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  • Paul Olesen

    Four Stroke Cylinder Head Reconditioning

    By Paul Olesen

    It's time to open up a can of worms and talk about a hotly debated topic in the powersport community - four stroke cylinder head reconditioning best practices. I've perused the forums and had discussions with people about reconditioning four stroke cylinder heads and there appears to be a lot of mixed opinion and beliefs on what is right or wrong. I'm certainly not going to say my take on the subject is the only way, but I do want to share my opinion, explain the technical details, as well as touch on the machining process. The text below is out of my book, The Four Stroke Dirt Bike Engine Building Handbook, and details why cylinder heads should be reconditioned a certain way.  Whenever new valves are installed in a cylinder head, it is best practice to recut the valve seats since the valves and seats are mated parts, otherwise the new valves are very susceptible to premature wear when run in the old seats. If a major overhaul is being performed, there is a good chance that enough seat wear will have occurred during the engine’s life that the valve seats will need to be recut before new valves are installed. This may be news to you, so I want to provide an explanation of why this is necessary. 

    The term concentricity is used to describe the relationship between the axis of two circular objects. When two objects are perfectly concentric, their axis match up precisely with one another. In the case of the cylinder head, the valve guide axis and the valve seat axis must be as close to perfectly concentric as possible and parallel to one another. Usually, guide to seat concentricity is kept around 0.001” (0.025mm) or even less for racing applications. This is achieved by the factory by using a manufacturing process where the valve guides are reamed first. Then the freshly reamed valve guide bore is used to center the valve seat cutter. Once centered, the valve seat is cut. This process is then repeated for all the valves and results in very good concentricity between the valve guides and valve seats. As the engine is run, the valve guides, valve seats, and valve faces will wear. The valve guides will wear from front to back in an oval shape at the top and bottom of the guides. In a cross sectioned view the valve guide will take on an hourglass shape. The guide will become oval as a result of thrust forces stemming from the way the camshaft contacts the lifter bucket or rocker arm. These forces are transmitted to the valves and cause the valves to thrust against the sides of the guides, eventually causing the guides to become oval shaped. Once the guides start to become oval shaped, the valve faces will no longer be as concentric to the valve seats as they originally were. When this happens the valves will start to slide against the seats, causing the seats and valve faces to wear. The valve seats will eventually become out of round and the sealing between the valve face and seat will suffer. Installing new valves into oval shaped guides and out of round seats will ensure that the new valves wear out very quickly!

    To ensure the new valves being installed last as long as possible, the cylinder head’s seats and guides must be reconditioned once they are worn out. Complete cylinder head replacement is always an option, but I want to focus on freshening up the original head which is usually a more economical option, but comes with many more variables surrounding the quality of the job.

    There are numerous services offered in the marketplace for valve seat cutting, however, not all valve seat cutting methods are equal in terms of quality. There are hand operated seat cutters, dedicated seat cutting machines, and a few other options to choose from. Selecting the correct seat cutting process and entrusting the work to a competent engine builder is very important. The valve seat cutting process should mimic the OEM process as closely as possible. A concentric valve seat will never be able to be cut without first servicing the valve guides. If the valve guides are out of round then they will either be reamed to a slightly larger size if they are not too oval in shape or they will be replaced. Once any issues with the valve guides are addressed and they are perfectly round from top to bottom, it will be possible to cut the valve seat. Ensuring the valve guide is perfectly round is extremely important since the valve seat cutter is centered off of the valve guide bore.

    Cutting the valve seat concentrically to the guide requires a combination of skill and using modern machinery. The best valve seat cutting equipment in the world is worthless without a good experienced operator running it. There are two main factors which make cutting a seat concentric to the valve guide difficult. To start with, the valve seat cutter uses a pilot which locates in the valve guide. Since the valve stems are very small in diameter the pilots used to guide the seat cutters are also very small in diameter. A small diameter pilot shaft that centers the cutting tool can flex easily, which presents a real problem when cutting the seats. The next issue that arises when reconditioning seats is that often times the cutting tool will try to follow the path of the old valve seat which can make it hard to cut a concentric seat. Couple these factors together with slop within the machine, setup error, and operator error and you can see how quickly things can come out of alignment and you can end up with a poorly cut seat. In addition to seat concentricity, the depth the seat is cut to will influence valve spring pressure, shim sizes, and the compression ratio of the engine. All three of these variables will be reduced the deeper the seat is cut, which is not a good thing. The surface finish of the seat itself will influence how well the valve seals. A seat with chatter marks or other machining blemishes will not seal as effectively as a smooth seat. The valve seat width and the contact point between the seat and the valve face are also very important. Due to the complexities involved with cutting valve seats on modern four-stroke dirt bike engines, the job should not be left up to just anybody. There are numerous businesses which specialize in valve seat cutting which have both the right equipment and expertise to do the job correctly. I highly recommend spending some time researching and finding a reputable cylinder head machining company when it comes time to recondition your head. If the cylinder head must be shipped off in order to do business with a reputable company, the additional wait will be worthwhile. If you found this information helpful and would like more technical info on maintaining your four stroke engine, check out my book, The Four Stroke Dirt Bike Engine Building Handbook. Thanks for reading and happy wrenching! As always if you have comments or want to share your thoughts please leave a note below.

    -Paul



    Available at: 
    - Amazon
    - Moto Fix Website
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  • Coach Robb

    10 Body Indicators That Tell You When to Workout & When to Back Off!

    By Coach Robb

    TIME TO REST - Pay attention to these 10 body indicators to gauge when to work out and when to back off!   If you don’t take time to rest and recovery, your body wont adapt to the stress of training and racing – and as a result you won’t get stronger or faster. If you neglect recovery for too long, you will start to lose strength and speed.   Here are some symptoms to look for: First your sleep patterns will be off (tired and you can’t sleep, restless sleep, etc.). Second your energy levels will be negatively affected. Third, you will begin to get sick more frequently (and take longer to heal from the virus). Fourth, your appetite will become suppressed.

    Remember, over training is not applicable only to elite athletes and professionals, recreational athletes have to balance, personal, professional, bills, children, inadequate sleep, etc. which is what makes recovering from your workouts and racing even more difficult.  
    Symptom Evaluation
    See if you are experiencing any of the following symptoms:   Symptom #1-Body Mass
    A 2% drop in weight from day to day indicates a body-fluid fluctuation. More than likely, you didn’t hydrate enough to offset heat, humidity, intensity and duration. Dehydration negatively impacts both physical and mental performance and could compromise the quality of your next workout or race.   Symptom 2-Elevated Resting Heart
    An elevated resting heart rate is a significant indicator of stress within the body. An elevated HR indicates that your nervous system is in that “fight or flight” mode which results in elevated hormone levels to provide more oxygen to the muscles and brain. Your body doesn’t know the difference between and physical and psychological stress. A hard day at work and/or a hard workout or race both require additional recovery protocols.   Symptom 3-Sleep Quality: you wake up and don’t feel fresh.
    Quality sleep: falling asleep quickly, deeply and staying there for a long period of time will allow your body to release the much needed growth hormone (hGH) necessary for rebuilding muscle and burning body fat. Several low quality nights of sleep will decrease your reaction time, immune system, can cognitive functions – not a good scenario when it comes to quality workout or high end performance on race day.   Symptom 4-Hydration: your urine is dark yellow
    Unless you are taking B vitamins, a dark colored urine can be an indicator of dehydration. Your urine is an easy indicator of your water levels throughout your body.   Symptom5-Energy Levels are Low
    Honesty is the key here. You know the difference between being tired and having low energy. Being tired is about recovering from yesterday’s workload. Being low on energy is a at a completely different level. Athletes think they can block out signs of fatigue and push to the next level of fitness, performance just doesn’t develop in this environment.   Symptom 6-Mood State: your moody (and even cranky).
    When your body is overwhelmed by stress (training, racing, work, family, etc.), it produces the stress hormone cortisol that can cause irritability and/or anxiety. Stress also halts chemicals like dopamine, a neurotransmitter in the brain that has a big bummer effect on mood when depleted. Crankiness means not enough recovery.   Symptom7-Sick Frequently
    Any illness or even a woman’s menstrual cycle, will increase your need for energy to refuel your immune system, which is having to work overtime. This translates into fewer resources available for recovery from training.   Symptom 8-Pain: your excessively sore or have a nabbing injury.
    Whether you are sore from over worked muscles or have an injury that continues to linger is an indicator that your body needs more energy to put towards the repair, which extends your total recovery time.   Symptom 9-Performance is sub-par.
    This is a subjective measure of workout quality, not quantity nor intensity. If you perform well on a particular workout, you would rate that workout as “good”. If you have a sub-par performance or feel like you are struggling to complete that same workout, you would rate that workout as “poor”. Trending workout quality – multiple poor workouts in a row – is one of the easiest ways to identify the need for more recovery.   Symptom 10-Oxygen Saturation: low oxygen levels.
    The amount of oxygen in the hemoglobin of the red blood cells can be measured and is thought to be an accurate assessment of recovery because of the association of high oxygen saturation levels and higher energy levels.   Evaluation Time: count how many of the above symptoms you have experienced over the last week and then compare this against the following:
    0-1: Green Light: you are recovering adequately and can maintain your normal volume and intensity
    2-4: Caution: You can complete your hard workouts; however, cut the workout short if you are struggling to complete the first couple of intervals after a long warm up
    5-6: Warning: This is the zone where you are close to tipping the scales and becoming over-worked, sick and injury prone. You need to add a second rest day to your week
    7-10: Danger: You are IN the danger zone and need to take one week completely off (no sport specific training); increase your high quality food intake and take 2 hour naps each day.   If you want me an my staff to review if you should take a break from training and racing, please feel free to contact us at Contact@CoachRobb.com.
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  • Coach Robb

    4 Reason (and solutions) Why Your Training is Making You Fat and Slow!

    By Coach Robb

    Mistake #1: Not knowing YOUR sport specific heart rate training zone Your maximum heart rate number changes specific to the sport that you are training and racing.  For example, your maximum heart rate on the motorcycle will be higher than on a bicycle (because of the amount of muscle you are using).  A frequent mistake athletes make is completing a maximum heart rate assessment within one discipline and then use the established heart rate training zones across all forms of training and racing.  An additional mistake is using the generic algorithms that are programed into heart rate monitors.  When you plug in your age, height, body weight and activity level, the watch is programmed to provide you GENERIC heart rate zones.  The most accurate assessment of your maximum heart rate is to complete field testing every 6 – 8 weeks. Solution #1: Complete Sport Specific Time Trials and Determine Your Maximum Heart Rate [Note: your maximum heart rate varies from sport to sport – the more muscle you utilize, the higher your heart rate] Your maximum heart rate changes as your aerobic engine improves.  The stronger your aerobic base, the lower your resting heart rate.  With this being said, your maximum heart rate will come down as well because the heart can pump the necessary amounts of oxygenated blood to the working muscles at a lower number because it is “stronger” and pumps more volume of blood with each beat.  Over the duration of my career, I have found the following field tests as a solid indicator of maximum heart rate along with muscular endurance: Swimming: 500 yards (capture your interval at each 100 yard interval) Cycling: 10 miles (capture your elapsed time and heart rate at the five mile and ten mile mark) Running: 3 miles (capture your elapsed time and heart rate at each mile marker) For physical strength, I have a customized Plyometric routine that I feel tests your lactate tolerance and anaerobic thresholds.  This test is EXTREMELY difficult and requires a doctor’s approval.  If you have your doctor’s approval and would like a copy of this Plyometric Assessment, please email me directly.   Mistake #2: Not Testing and Evaluating Your Training Efforts Correctly When you complete your maximum heart rate assessments through time trials, you want to make sure that you are not fatiguing the muscles too quickly which keep you from accurately testing the strength of your heart (specifically oxygen volume as it fuels your working muscles with oxygenated blood). Keep in mind that there is a difference between muscular endurance and muscular power.  If you muscles fatigue due to excessive load or exertion, you will not push your heart into its upper limits.  The key is knowing how to evaluate your time trial results.  Below mistake number three, I will outline testing protocols along with how to evaluate them correctly.  Solution #2: Allow for an Adequate Warm Up When you are attempting to test your aerobic engine, you need to make sure that you don’t increase your intensity too quickly for two reasons. First: the muscles need adequate time to warm up (usually 20-30 minutes) so that you don’t use the first half of your assessment as your “warm up”.  Second: trying to hit maximum effort too early.  The idea is to see what your maximum is over the entire duration, not the first five minutes.    Mistake #3: Following a Generic Training Plan Following a generic training plan that doesn’t take into consideration your training background, physical abilities and availability of time to train will lead to performance plateaus, illness and injuries. Within our performance programs, we factor in your testing results, physical limiters (see Mistake #2), goals and objectives as we develop your training program.  Too frequently I interview new clients who are frustrated with their last year of training and racing because they don’t see any improvements despite the consistency in their training.  The reason for this is that the efforts are not being quantified and the athlete spends too much time in the “grey zone” that yields little to no improvements in performance.  Solution #3: Begin Following a Scientifically Backed Training Program If you would like to begin maximizing your training efforts, please email me and let’s get a nutrition & performance program built for you ASAP!  I guarantee that you will burn body fat, build muscle and improve both your speed and endurance in as little as 12 weeks.  Stop the insanity of training without a plan and email me today.   Mistake #4: Not Eating Enough Fat, Protein and Raw Fruits & Vegetables Many athletes become fat and protein phobic because of the misinformation that is floating around on the internet and morning shows.  The truth of the matter is that the body needs more protein and fat than you can even begin to imagine. Simply put, lean protein re-builds torn down muscle.  If you want to build more muscle you have to eat protein.  Lean protein also supports your immune system which helps protect you against viruses and being down and out being sick. Clean fat will help your body recover from the oxidative stress of aerobic exercise (at all intensity levels).  Eating raw fruits and vegetables will provide your body with the necessary vitamins and minerals to both produce energy as well as recover from your daily training.   Solution #4: Begin Eating More Protein, Fat and Raw Vegetables & Fruits to Burn Body Fat and Improve Your Speed & Endurance The only two things that satisfy appetite is fat and protein – NOTHING ELSE.  If you are on a low fat, low protein diet, you will never experience the true feeling of being full.  This will negatively affect your ability to sleep (which makes you gain weight because your body doesn’t have the chance to release human growth hormone (hGH) which is responsible for making you lean).  The key to burning fat and building muscle is to satisfy your appetite so that you can sleep deeply (REM patter three).  When you get to REM pattern three your body rejuvenates from the inside out and allows your body to release human growth hormone naturally – you will wake up both refreshed and leaner.  However, it starts with real, raw fruits, vegetables, high quality fats and lean protein. You can now see that by training with a scientific, yet simplistic approach will yield the long-term results that you have been always wanting.  I look forward to hearing from each of you and how me and my staff can help you and your program. Until next time, Train Smart-Not Hard! -Coach Robb   About Coach Robb and MotoE (CompleteRacingSolutions.com)  Coach Robb has been working with riders and racers since 1987 and is the founder of the Complete Racing Solutions Performance System, the Mental Blueprint of Success, the MotoE Amateur Development Program, the MotoE Educational Series and a nutritional consultant to Nutritionally Green Supplements based out of Orlando Florida. CompleteRacingSolutions.com is a premium resource center for motocross, supercross and GNCC riders of all abilities and ages.  Visit CompleteRacingSolutions.com & subscribe to his monthly newsletter that outlines the training solutions used by Factory KTM/Red Bull Ryan Dungey, Geico Honda's Jeremy Martin, Factory KTM/Red Bulll Alix Martin, Factory Kawasaki/Pro-Circuit Adam Cianciarulo, multi-time Loretta Lynn & Mini O Amateur Champion Jordan Bailey (Factory Rockstar/Husqvarna), Factory KTM/Red Bull Broc Tickle, Factory Kawasaki/Pro-Circuit Stilez Robertson, off road riders Charlie Mullins (Factory KTM/Red Bull), Chris Bach and Ryan Overton along with quad racer Roman Brown (Factory Yamaha) along with thousands of riders all around the world who have families, hold full time jobs and just love to ride and race motorcycles.   Instructional videos with Coach Robb can be found on the Coach Robb’s YouTube Channel addressing rider’s questions about speed, endurance, strength, nutrition, biomechanics, stretching, and soft tissue maintenance. You can also find articles and videos at CompleteRacingSolutions.com relevant to riders of all abilities.  If you are into social media, you can find him on Twitter: @MotoCoachRobb, Instagram: CoachRobbBeams and Facebook: Coach Robb.  If you are into podcasts, CLICK HERE for his first three shows where he outlined: How to Eat Healthy on $10 a Day; Importance of Sleep and It's Influence on Weight Loss; The Dangers of Over-Hydrating.    
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  • Paul Olesen

    Checking and Setting Cam Timing

    By Paul Olesen

    Today I'm going to cover how to check and set cam timing, which is something you can do if you have adjustable cam gears in your engine. This is a procedure often performed by race engine builders to ensure the valvetrain performs just as they intend, and ultimately so that they extract the desired performance out of the engine. Adjustable cam gears typically aren't a stock option but are abundantly available in the aftermarket. The following text is exerted from my book, The Four Stroke Dirt Bike Engine Building Handbook, so if you find this info valuable please take a look at the entire book.  

    Degreeing the camshafts is the process of checking, and if necessary altering, the cam timing so that the timing is set perfectly to specified timing values. On stock and performance engines, cam timing can be off slightly due to manufacturing variations in parts such as the camshafts, cam gears, cam chain, cylinder, cylinder head, crankshaft, crankcase, and gaskets. With so many parts having an influence on cam timing, it is necessary to adjust and correct the timing so it coincides precisely with the desired timing values.  The biggest factor determining how the camshafts must be timed is whether the cam lobes are symmetrical or asymmetrical. Camshaft lobes that are symmetrical have opening and closing ramps that share the same profile. Asymmetrical cam lobes have opening and closing ramps with different profiles. Symmetric and asymmetric camshafts are timed differently. First we will focus on the timing of symmetrical camshafts. Symmetric camshafts are timed most accurately by determining the position of the camshaft’s lobe center in relation to crankshaft position. A camshaft’s lobe center is where peak lift occurs, which is the most important timing event of the camshaft. Since the tip of the camshaft is rounded, it would be difficult to determine the lobe center by taking a direct measurement of peak valve lift. The opening and closing points of the camshaft are also of little use because the cam opens and closes gradually. This makes it difficult to determine the precise position in which the camshaft opens or closes the valves.

    The lobe center position is a calculated value based on the position of the camshaft at two specific points of valve lift, typically with valve clearances set to zero. Normally the position of the camshaft is recorded at 0.050” (1.27mm) of lift as the valve opens and 0.050” (1.27mm) of lift when the valve closes. By recording the position of the camshaft at a specific valve lifts, the cam lobe is on a predictable portion of the opening and closing ramps. The center of the cam lobe is exactly in the middle of these two measurements. To calculate the lobe center of a symmetrical cam lobe you will need to do the following: 
    1. Add the measured opening and closing timings together
    2. Add 180 degrees to the sum
    3. Divide the answer by 2
    4. Subtract the smaller value of the two opening and closing numbers from the answer to reach the lobe center value.

    Once the actual lobe center value has been determined on the engine, it can be compared to the specified lobe center timing presented by the manufacturer, aftermarket cam supplier, or the engine tuner. If the measured lobe center position coincides with the targeted position, all the work is done. If not, the cam gear will need to be adjusted so the timing is corrected. 

    If you are checking the timing on stock cams and lobe center information isn't presented, you will need to determine the lobe centers the manufacturer recommends. To do this, the opening and closing timing information supplied in the service manual can be used. Aftermarket camshafts should come with a timing card full of useful information to set the cams correctly if they are adjustable, otherwise the lobe centerline can be calculated if the opening and closing timings are known. If you don’t like math, there are plenty of lobe center calculators available on the internet you can use. 

    For the Kawasaki KX250F engine with the stock camshafts, the timing information is as follows: 

    Intake Opens 40° BTDC (Before Top Dead Center)
    Intake Closes 72° ATDC (After Top Dead Center) 
    Intake Lobe Center = ((40 + 72 + 180) ÷ 2) - 40 = 106° 

    My calculated lobe center timing is 106°. When I check the cam timing, this will be the value the real engine hopefully yields. The lobe center for the exhaust cam can be found the same way. For the KX250F exhaust cam: 

    Exhaust Opens 69° BBDC (Before Bottom Dead Center)
    Exhaust Closes 49° ATDC (After Top Dead Center) 
    Exhaust Lobe Center = ((69 + 49 + 180) ÷ 2) - 49 = 100°  Something not obvious I want to touch on is that if the intake opens after top dead center, a negative value for the opening should be used. If the exhaust closes before top dead center, a negative value should be used here as well.

    To start the process of checking the timing the valve clearances should be set to zero. Thicker shims can be used and zero clearance can be confirmed with a lash gauge. A degree wheel and pointer will need to be installed on the engine. There are many ways of attaching these items and each engine will provide its own challenges.

    Here I’ve left the flywheel on and installed a couple washers behind the degree wheel to space the degree wheel from the flywheel. Then the flywheel nut is used to secure the degree wheel. The pointer can be made from welding rod, a coat hanger, or anything else you can find. I’ll be finding TDC with the cylinder head installed, so I used one of the exterior head bolts to secure the pointer. If you will be finding TDC with the head off, choose another location. 



    Before the cams can be timed, TDC must be found. This can be done with the cylinder head on or off depending on the process you use. The piston dwells a few degrees at TDC so more accuracy than zeroing the degree wheel to the piston’s highest position is necessary. Similar to finding the cam lobe center, TDC can be found by measuring equal distances on the piston’s up and down stroke and then confirming that the degree wheel timing is equal on both sides at the measured distances. Dial indicators or piston stoppers are commonly used to do this. 

    HOT TIP: Piston stoppers can easily be made by removing the center section of a spark plug and then tapping a suitably sized threaded hole in the remaining part of the plug so a bolt and lock nut can be installed. The stopper can then be easily threaded into the spark plug hole. 

    Whichever method of finding TDC you decide to use, start by moving the crankshaft to the approximate TDC position. Then without rotating the crankshaft move the degree wheel so that TDC on the wheel coincides with the pointer. Next, set up your piston stops or measure piston travel on both sides of TDC. In this example I’m using a dial indicator which extends through the spark plug hole down into the cylinder. I’ve decided to take measurements at 0.050” (1.27mm) of piston travel before and after TDC. At each measurement point the number of degrees indicated on the degree wheel before and after TDC should be the same if I have found true TDC. 



    If the degree wheel values don’t read the same before and after TDC determine which way the wheel must be rotated so that the values become equal. Then carefully rotate the degree wheel without rotating the crankshaft to alter the degree wheel’s position. Once altered, recheck and confirm that true TDC has been found. This can be a tedious process but is extremely important for checking cam timing accurately. Repeat the procedure for checking TDC 3 - 5 times to ensure repeatability and accuracy.

    After true TDC has been found, be extremely careful not to inadvertently move the degree wheel or pointer. Do not rotate the crankshaft using the nut securing the degree wheel to the crankshaft. Instead, use the primary drive gear nut or bolt to rotate the engine over. 

    Next, set up a dial indicator on the intake or exhaust lifter bucket, depending on which camshaft you are checking. You’ll have to use some ingenuity here in determining the best way to secure the dial indicator to the engine. I’ve used a flat piece of steel and secured it to the cam cap using the cylinder head cover holes. Make sure the indicator travels as parallel to the path of valve travel as possible for accurate readings. Also makes sure at least 0.060” (1.52mm) of travel from the indicator’s resting position is possible so adequate valve lift can be measured. 



    Once the indicator has been set up, the cam timing can be checked. Whenever checking timing only rotate the engine over in the direction of engine rotation. Reversing engine rotation will result in inaccurate measurements due to the reversal of gear meshes and chain slack. If you miss a measurement point, rotate the engine over until you get back to the previous position. 

    Slowly rotate the engine over until 0.050” (1.27mm) of valve lift has occurred. Then record the position of the degree wheel. Next, rotate the engine until the cam begins to close the valve. Once only 0.050” of indicated valve lift remains record the position of the degree wheel. Repeat this process of checking opening and closing positions 3 - 5 times to check for repeatability before calculating the cam lobe center. 

    Once you are confident in your measurements proceed to calculate the cam lobe center. On the KX250F engine my intake lobe center is as follows: 

    Measured Intake Open (0.050” Lift) 39 ° BTDC
    Measured Intake Closure (0.050” Lift) 74 ° ABDC 
    Intake Lobe Center = (( 39 + 74 + 180 ) ÷ 2 ) - 39 = 107.5° 

    On my stock KX250F engine the actual lobe center is 107.5°. At this point if I had adjustable cam gears, I could rotate the gear slightly so that the lobe center corresponded to the specified lobe center value. The same procedure is followed for checking and adjusting the exhaust cam timing. Remember if mistakes are made when setting cam timing big problems can result, so it is best to be very patient and focused when performing this task. Always check your work 3 - 5 times to make sure the timing is repeatable and making sense. When tightening adjustable cam sprockets, use a locking agent and be sure to torque the bolts to their specified values. 

    When working with single camshafts that have both the intake and exhaust lobes ground on them, focus your efforts on achieving correct intake timing. Correctly setting intake timing is more important since it has a larger effect on power. The intake valves also have higher lift than the exhaust valves, potentially creating clearance troubles between the piston and valve if the intake valves are mistimed.  

    With your new fangled ability to adjust cam timing, you may be wondering what happens if you advance or retard the intake and exhaust cams from their standard positions? The lobe separation angle refers to the number of degrees which separate the lobe center of the intake lobe from the lobe center of the exhaust camshaft. The lobe separation angle can be calculated using the following formula:

    LSA = (Intake Centerline + Exhaust Centerline) ÷ 2 

    As a rule of thumb, reducing the lobe separation angle by advancing the intake and retarding the exhaust camshaft will increase valve overlap, move power further up the power curve, increase cylinder pressure, increase the chance of detonation, and reduce the piston to valve clearances. On the contrary, increasing the lobe separation angle by retarding the intake cam and advancing the exhaust cam will have somewhat of the opposite effect. There will be less valve overlap, power will move to a lower RPM, chances of detonation will be reduced, and the valve to piston clearances will increase.



    The likelihood of finding more or better power by advancing or retarding the camshafts is not all that likely because manufacturers, tuners, and aftermarket companies already test specific combinations of cam timings to death. In addition, if the lobe separation angle is reduced, the piston to valve clearances should be checked to ensure they are adequate. My advice is to run the prescribed cam timings to reduce the chance of problems occurring.

    Asymmetric camshaft timing can be set in a similar fashion to symmetric camshafts, however instead of focusing on the lobe center position, the specific opening and closing points will need to be measured. Timing cards supplied with asymmetric cams should have specific instructions for setting timing, but normally valve clearance is set to zero and cam positions are recorded at specific lift heights. Based on the measured opening and closing positions, adjustments are made to the timing until the timing matches the specified values.

    I hope you enjoyed this exert on checking and adjusting cam timing. As always feedback is appreciated so please leave comments below. 

    If you're interested in more engine building info check out my book The Four Stroke Dirt Bike Engine Building Handbook. Right now we are having a 4th of July Sale where everything on our site is 20% off with the discount code fourthofjuly2017. Just be sure to enter the code upon checkout so you receive your 20% off!  So if you've had your eye on our Four Stroke Dirt Bike Engine Building Handbook or even our Value Pack, but haven't pulled the trigger yet - go for it!
      Availabe at: DIYMotoFix.com - Paul
    • 2 comments
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  • Scott Meshey 141

    The Beginning of the Journey

    By Scott Meshey 141

    I’M BACK! Hello ThumperTalk readers! My name is Scott Meshey. If you’re from the Motocross community there is a good chance you might know me through my blog series from Vurbmoto “Life with the Mesheys”, if not, please check my profile. Get to know me, and I hope you follow along with this blog series. For this entry, I’ll dish out some background and where I am headed right now, kicking off the start of the series. So let’s get to it! My blog series for Vurbmoto ran for 3 and a half years until their recent shutdown. The opportunity to share my experiences through Vurb and now on ThumperTalk is something I truly enjoy. This blog series will follow my progression, good, bad, and everything in between to the pro ranks, sharing my experiences and wisdom I gain along the way. Whether you ride the trails on the weekends, hit the back roads after work, are a serious racer, or a parent of a racer, I hope my experiences give insight not only to just Motocross racing, but I hope they give a unique perspective of the challenges behind the goggles. I want readers to enjoy reading my experiences, but I also want others that aspire to achieve the same goals as myself, particularly the youngsters of the sport, to learn from these blogs in their quest to be the best.  I’ve been riding since I was 4. I started competing at amateur Motocross nationals when I was about 9 or 10 years old, contending at the Loretta Lynn’s Amateur Motocross National 9 years in a row, the Winter National Olympics or “Mini O’s”, the RCSX at Daytona, the Lake Whitney Spring Championship, the Mill Creek Spring Classic, and the JS7 Freestone National Championship. I’ve ridden for several amateur teams, and had the privilege of working with some legends of the sport. In 2016, I jumped into the pro Arenacross series for a few rounds to get experience in the pro ranks. Unfortunately, my experience was cut short by unresolved health problems from a bad case of pneumonia in 2015.    Loretta Lynn’s 2015, Picture by Sarah Behrens Photography  This brings me to where I am today. After hitting the reset button and off the bike for a year, I’m back home in the motocross scene, eager to continue sharing my story and experiences with the dirt biking world, back to good health with amazing people behind me. I’ll be going to Loretta’s for my 10th year in the 250A and Open Pro Sport classes, and jumping into the pro Motocross series thereafter.  Come along for the ride and tap/click the follow button! I’ll see you at the races. Scott Meshey #141
     
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Our community blogs

  1. Frequently I discuss the importance of proper hydration and nutrition as it relates to building and repairing muscle tissue, burning unwanted body fat and consuming enough water, sugar and electrolytes to perform optimally every day when you head out the door.

    With this in mind, I want you to begin keeping a very detailed analysis of your sweat rate. Nutrition as it relates to performance is an interesting subject; we look at the quality and quantity of your food intake and evaluate if you have enough energy to finish your workouts feeling strong throughout the duration of the workout. If you begin to fatigue, we know that we need to adjust the quantity (we assume that the quality is there at this point).

    Now let’s take a detailed look at your hydration as it relates to your performance. Proper hydration is going to affect your body in two ways: one, it helps you regulate your core body temperature. The cooler you are from the inside out, the better you will perform.

    The second benefit to proper hydration is that your muscles (and brain) are receiving enough water, electrolytes and sugar to perform properly: good mental clarity and strong muscle contractions.

    To improve your confidence on race day, you need to know what your sweat/replenishment rate is specific to your intensity with the factor of temperature & humidity. Though it sounds tedious during the week, it is invaluable on race day – you will know exactly what your hydration strategy to implement to race up to your fullest potential.

    Until next time, work smart - not hard!

    -Coach Robb

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  2. Had a great day of riding Saturday with my buddy @Bryan Bosch in the Withlacoochee National Forrest just north of Dade City, Fl. It's still pretty wet from the summer rains and Hurricane Irma didn't help! But, like always, the 701 took everything in stride, even with worn Continental TKC80 tires. Well, "almost" everything...

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    Unfortunately, the trail riding portion of the day got cut short because of a little mishap that resulted in my clutch perch letting go of the handlebars...

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    As we left the sandy trails, turning onto a damp, hard-packed clay road, just a tiny little goose of the throttle caused the bike to walk sideways into an unrecoverable low-speed drop...

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    Since the fall seemed so minor, I was surprised to see that the pinch bolt for the clutch perch had pulled out the threads! Uhhhhh, this is the "Enduro" model, not the wimpy SM version or even more girly-man KTM 690 Enduro R! IT'S a HUSKY!!!!! ;)

    Fortunately my riding partner is a zip tie junkie, so we patched things up enough to get 'er home.

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    When I got it home, I noticed that the threads went quite a bit deeper than the factory installed bolt was taking advantage of, so I was able to thread it back together using a longer bolt. Clearly this is a bit of a weak spot on the big girl, so I'll be installing REAL hand guards shortly.

    What hand guards do you guys like? Hit me up in the comments section below and don't be afraid to share your pictures. I'd love your help in picking out a pair of hand guards. Time to replace the stock wannbe  "bug guards" er, huh... "hand guards". 
     

    Bryan Bosch
    Steve Claus
    #dualsportduo

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    Moto the big girls? Thought about it!!!! ;) - Dade City MX park on the way home. At least the KTM comes with full wrap around hand guards.

  3. Scott Meshey 141
    Latest Entry

    Hello ThumperTalk readers! Been some time since my last post. After Loretta’s some take a small break, which is good for the body and for re-evaluating plans going forward. For me, it’s been a mixture of both.

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    Things have been calm or the calm before the storm, Hurricane Irma, yet hectic in the Meshey camp. The rush and intensity of getting to Loretta’s is over. Next the new academic year; college starting, sponsorship season renewing, training, and then throw a hurricane in the mix… it’s safe to say that things continued to stay busy for me. However, to be honest, I wouldn’t have it any other way! Looking back just a year ago, I was  not cleared to start physically training yet by my doctor, no running or working out, no riding or bikes, and unclear when I was going to be able to race again and questioning if I would regain my standing within the racing community (don’t mess with the flu, kids). I knew I had the ability, but how long was this going to take get up to speed from my last national gate drop in 2015. It does not happen over-night and learning to be patient, can be hard when you breathe racing. I am pleased with my progress and recognize that you have to be grateful and appreciative of your own evolution, it’s not about where everyone else is…it’s about you and your efforts.

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    Loretta Lynn's Amateur Motocross National 2017

    Some really cool things have happened in the months of August/September, lots of new opportunities. One of those  being the opportunity to write for Wiseco on their Racer Elite piston, so be sure to keep watch on their site or stay tuned to my profile/blog series, I will be posting the link when it is up and running, the product is awesome and the new relationships formed from giving valuable feedback has proven to be not only in the products performance, but those who work within the company, it’s a great group of people and I am thankful for the new avenues to explore. Also, I had the privilege of being EVS’s athlete of the month for September! (Link: http://evs-sports.com/explore/blog/athlets/scott-meshey/ ) Despite my time off, they have stood behind me and continue to do so through the good and the bad. Thanks Brad!! Along with a few new product review opportunities, including the Fly Tri-Pivot levers, Excel/FasterUSA wheel build, Race Tech Engine Services, and the Acerbis X-Seat. I’ll be putting all those products to the test to see how well they hold up, how well they perform, and if they add an edge to your racing program. I will also be adding new video content to my blogs and reviews using the new SENA Prism Tube camera, putting it through the paces to show its capabilities.

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    So, what are my plans going forward? Balancing college, work and training isn’t exactly the easiest, but where there is a will there is a way, if you want something bad enough you relentlessly pursue every avenue, no matter the obstacles, for those are just challenges to test you, to live to your fullest potential. The focus to continue building through practice and hitting races in my area, along with the Evergood Open  race. I’m looking forward to re-connecting with those who have given me the chances to evolve as a racer, the track looks awesome and good times to be had by all. Mini O’s is the next national and is probably my favorite national of the year, between the atmosphere of the race and the track, it has the feel of a family-oriented event, Thanksgiving and Mini O’s, go together if you are a racer. From there, Arenacross and spring nationals. Thankfully, I have already learned the basics of Arenacross and the process of pro race day and it will allow for a better result and not something that will come as a shock to me as previously. My health, breathing in particular, working with me instead of against me,  Lots of exciting things coming up!

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    MXGP Amateur Race Day @ WW Ranch, photo by MEPMX

    This entry may seem short, but there is always more to come from me! Be sure to stay tuned to the blog series and click/tap the “follow” button to stay updated on any new entries! You can also click the “follow” button on my profile to stay updated with anything I post on ThumperTalk. Thanks for following along, I’ll see you at the races!

  4. This week I want to talk about two-strokes. To kick off this post I have some awesome news. The Two Stroke Dirt Bike Engine Building Handbook is off to the printers and will be available for pre-sale very soon! Getting the book off the ground has been no cake walk. It's been two years coming and we are so thankful our riders and fans have been patient with us! At the end of this post I'll give you instructions on how you can stay updated on the launch. With that said, let's get started. Today's post aims to provide an overview of the important aspects of the two-stroke cylinder and answers a couple commonly asked questions relating to cylinder modifications.

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    The ports found within a two-stroke cylinder in combination with the exhaust system have the greatest influence on power, torque, and the RPM at which maximum power is created out of the various engine subsystems found within a two-stroke engine. Typically when a new engine is designed the port characteristics are one of the first parameters to optimize. With this being the case they are also one of the first things anyone planning on altering an existing engine should consider improving or tailoring to their specific application. A two-stroke cylinder consists of exhaust, transfer, and occasionally inlet ports (true inlet ports are only found on piston or rotary valve controlled engines). The port heights, widths, areas, directions they flow, and relationships to one another all have a significant influence on how the engine will behave. The cutaway of the cylinder shown details the port arrangement and common nomenclature.

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    The inlet port/passage delivers air into the engine’s crankcase, most commonly through a reed valve, on a dirt bike engine. On older engines, a rotary valve or the piston may also be used to control the opening and closing of the inlet port. On modern machinery, the inlet simply connects the reed valve to the cylinder or crankcase. In this case, the primary restriction in the inlet port is the reed valve and as such the valve’s geometry and flow capabilities often dictate the inlet port's performance.

    The transfer ports are responsible for moving fresh air and fuel up from the crankcase into the cylinder. This occurs as the piston travels downward after the cylinder has fired. Once the piston uncovers the tops of the transfer ports the blowdown phase is complete, at which point much of the exhaust gas has been expelled from the cylinder. As the transfer ports begin to open, the exhaust pipe sucks fresh mixture up through the transfer ports into the cylinder. To a lesser extent, the downward motion of the piston also aids in creating a pressure differential between the crankcase and cylinder. The shapes and flow capabilities of the transfer ports play a big part in how effectively the cylinder can be scavenged of exhaust gases and filled with fresh air and fuel. The transfer ports also help cool the piston.

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    The exhaust ports dictate how much and how well exhaust gases depart the cylinder. Similar to the transfer ports, the duct shape, angle, length and volume have a large influence on how well gases can flow through the port. Typically, dirt bike engines commonly feature bridge port or triple port designs.

    General insights into a cylinder’s performance can be made by characterizing attributes such as the timing of the exhaust and transfer ports, the port widths, and the directional flow angles, but a deeper analysis is required to truly optimize a cylinder. Today, tuners and designers rely on computer software which computes a port’s specific time area (STA). As defined in the EngMod 2T software suite, “STA provides an indication of the effective port window area that has to be open for a certain length of time to allow enough gas to flow through the port to achieve the target power at the target RPM for the given engine capacity”. STA values are used to quantify the exhaust, transfer, and inlet port geometry as well as the blowdown phase of the two-stroke cycle. The blowdown phase occurs between exhaust port opening and transfer port opening and is one of the most important parameters in predicting engine performance.

    By manipulating STA values and subsequently the height, shape, and size of the exhaust, transfer, and intake ports, an engine’s power characteristics can drastically be altered. Port modifications can be made which allow more air to move through the cylinder, ultimately increasing the power of the engine. Conversely, ports can be filled or welded and reshaped which tame the engine and provide less peak power but a broader spread of power. Simple modifications to the ports can also be carried out which improves the air or exhaust gas flow through the port yielding better cylinder scavenging.

    Can I modify my own cylinders?
    Unless you have a deep passion for two-stroke tuning, are willing to spend money on software and porting equipment, and are comfortable throwing away botched cylinders, I would recommend having a reputable professional carry out any desired port modifications. Experienced tuners have developed a number of porting combinations that will work well for various makes/models and riding applications which will take the guesswork out of the situation and provide you with a good performing cylinder.

    Who should consider two-stroke porting modifications?
    For the sake of simplicity, I will lump porting modifications into two categories: major and minor.

    • Major port modifications would include tasks such as significantly changing the port timings (by either removing or adding material), altering the shapes of the ports, or changing the directions the ports flow. Anyone drastically altering their engine, such as turning an MX engine into a road racing engine, should consider major porting modifications. Other examples of applications that may require or benefit from major port modifications include drag racing, hare scrambles, ice racing, or desert racing.
       
    • Minor port modifications would include basic tasks such as removing casting flash, slightly altering the ports to achieve the stock port timing, and correcting areas that result in minor flow deficiencies. Just about everyone could benefit from these types of corrective actions; however, if the engine is already performing or producing adequate power, they often aren't considered. 

    I hope you enjoyed this writeup on key features affecting the performance of two-stroke cylinders. To stay officially updated on The Two Stroke Dirt Bike Engine Building Handbook we created an email sign up for our readers. Click this link to see the new cover, the Table of Contents, and some sneak peek pages right from the book.

    Thanks for reading and have a great rest of your week!

    -Paul

    The Two Stroke Dirt Bike Engine Building Handbook

     

  5. THE OFFICIAL TOUR VIDEO...Enjoy!

     

    The day started early. We wanted to get going early as the route was formidible and there was a high likelihood that we couldn't all make it to the other side. In fact, I didn't even call ahead and get hotel reservations. I was pretty certain we stood no chance.

    The day's ride was not long in distance, but in difficulty, it was overload. I had done the route once before as I rode it solo. Looking back on it, I realize I am an idiot. I am working on a solo documentary project and this route was the culmination of the film. So I rode it solo, filmed it solo, and suffered all by myself. The film is in post production at the moment and will be coming out in the next few months, at least that is the plan.

    As for the four of us, we had a plan to reach the pass at no later than 3pm. Any later and we would have to come back the way we came, defeated. All gassed up and ready to ride hard, we headed up the canyon to the trailhead.

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    The anticipation was high. Fernando Puga, who I just call Puga, told me that there is no option other than to reach the other side. He's a tough fella and a good rider. To put it in perspective, he is a bronze finisher in the 2017 Redbull Romaniacs. He is one of the top riders in Peru. He was determined.

    His buddy, Duilio, who stands at about 6ft 4inches give or take a few inches, is a beast. He, also, had no intention to give up. We either made it or we made it. No other options.
    In addition, there is Alex. He is my riding buddy from Cusco. This guy has a story to tell. I won't give it all away now, but he is as short as they come. I call him Chatito. That means "Shorty" in Spanish. He is starting the inning with a couple outs. His feet hardly can touch the ground when he mounts up on his KTM 300. However, the boy can ride.

    The plan was to ride steady. No long stops. I was the only one who knew just how tough it would be. Alex had seen parts, but not very much of the trail. We began pounding through obstacle after obstacle. They just kept coming. Relentless, gut wrenching, head exploding obstacles that scream at you to quit. One by one, we conquered. I am not sure how many times the guys asked me if we were close, but it made me chuckle each time.

    There were a number of "filters" that we would face on the climb to the 15,800ft pass. Each one posed its own set of problems. The technical part was enough to make one give up. However, add the altitude to that, and the will to continue dwindled to hardly anything.

    It was a privilege to watch these guys battle the mental part of this journey. None of us had it in us to finish. However, there was something about the makeup of the team, that compounded the energy we had left, and turned it into a reserve for each other when we needed a little bit more boost. Somehow, we pushed through each obstacle to get closer to the top.

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    One of the obstacles, that is properly named for the biblical scripture painted in graffiti on the rock, is the Stairway to Heaven. The words say that the day of God is soon.  Pretty much spot on. We spent an hour climbing 100 feet of elevation. There are 13 switchbacks, and enough rocks to build a quarry. Literally a one foot lunge forward on your bike was all one could do in most parts. It was a war. Each in their own battle, working their way to the top. The arrival at the top was met with a view of the upper valley, a long break to recover from the chaos, and a bunch of fluids and protein which would lead us to the next set of filters that would certainly break us down some more.

    It seemed like forever, but we finally pushed through all of the obstacles to the pass with exception of the pass itself; a 15,300ft rock garden with an incline that makes me want to cry just thinking about it. One by one, we arrived at the top. Somehow, everyone made it.

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    I remember Puga asking about the downside of the mountain. He had this idea that it would be "just" a downhill. I chuckled again and informed him that we were not done with the filters. Just because its downhill, doesn't mean it's easy. After a short celebration on the top, our heads were ready to explode from the altitude. Air was light and nothing could get us off that mountain fast enough. Down we went.

    The highest altitude area is full of rock. We had to navigate hundreds of steps and drops to bring us down toward the Cuncani Valley. With our tongues hanging out, we pounded down the edge of the canyon. Little by little, the air began to provide more oxygen as we reached the 14,000ft range. It's crazy to think that one would be happy to breath the thin air at that altitude, but when you compare to the pass, we were happy with 14k.

    Before long,  the hot springs that awaited our arrival was on the forefront of each of our minds. Cramping arms, legs that no longer wanted to properly stand on the pegs, and minds that were exhausted from the 7 hours of intense concentration were beginning to let each of us know that the day was just about over.

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    We reached the little community of Cuncani and found a new dirt road that had been cut, which we were happy to use to reach the hot springs. It wasn't long before we found ourselves pulling into the hotel and pool area, ditching our gear and plunging into the steaming mineral water to soothe our hammered bodies.
    The ride was something only one could dream about, with the exception of the four of us. It's a privilege to be able to do this. Finishing a day of riding in this manner should always feel this good. I am so stoked to have shared and fought the trail with these guys. I can't wait to try the next impossible!
    Stay tuned for the next adventure!

    Scott

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  6. Hey ThumperTalkers, checkout my latest off-road motorcycle riding video tip on the proper techniques necessary to navigate rutted corners with speed, control, and confidence. Of course, if you have any questions, hit me up in the comment section below and I'll do my best to answer. Please be patient, I'm at the track and events a lot, but I'll do what I can!

    How would you rate your skills in tackling rutted corners? What's giving you the most trouble?

     

    Brian Garrahan
    http://garrahanoffroadtraining.com/
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  7. UNLV Rebel MX Club
    Latest Entry

    What is the Rebel MX Club up to today?  We have a lot planned for this upcoming school year and we are excited to tell you about it.  Our purpose is to grow the dirt bike community and that is what we plan to do! In Las Vegas, Nevada, our riding season is from October until March so of course we will be doing lots of riding and camping and having a good time but we also plan to expand the dirt bike community! In the spring of our last school year we held our first ride day where we taught 3 brand new individuals how to ride a dirt bike! We started the students out on a CRF 50 to learn some throttle control and shifting up into the next gears and coming to a stop. Once the students felt more comfortable we moved them on up to a CR 85 or a CR 125 depending on their size.  We put together a short little video of our first ride day on our youtube page if you'd like to go check it out at this link:

    For this upcoming Fall semester we have six Learn How to Ride Days planned and we are stoked to teach some new people how to ride a dirt bike but we need the dirt bike community's help!!  Our awesome student government called the Consolidated Students of the University of Nevada, Las Vegas (CSUN) has granted us $1000 to buy a dirt bike to teach our students on.  We are currently searching for a dirt bike to purchase for our club. If you or someone you know is in the surrounding area of Las Vegas, Nevada and have a dirt bike that you would like to sell please let us know! We are also looking for some possible donor bikes that might need a little work that anyone would like to donate to our club.  The more bikes that we have means more students and community members we can have learning.  If there are any vendors or reps out there that would like to sponsor some gear to keep people protected we would greatly appreciate it and would be proud to represent your brand. The same goes for gear as it goes for the dirt bikes, we would greatly appreciate some old donor gear or hand me downs that you would like to donate.  If you would like to help the Rebel MX Club achieve our goals you can contact us on our Facebook Page: UNLV Rebel MX Club or through our email at rebelmx.unlv@gmail.com or leave us a comment in the bottom of our blog! Our general meeting and first ride day will occur on September 6th and 9th. We will post more about the details on our Facebook Page. Anyone is welcome to come, you don't have to be a UNLV Student.  Thanks for reading. We will post an update on our first ride day after it occurs.  Keep on braaaaping.

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    Sure, it's fun to put some laps in on a motocross track. But, you'll fall short of your potential if you're not using this key practice law of practicing important techniques separately. This is true for motocross cornering skills as well as motocross jumping skills. Did you know that riding really well requires mastering as many as 55 separate techniques, all laced seamlessly together?

     

     

    If you'd like more of my riding tips, browse my blog here on ThumperTalk or my website. If you'd like to be notified when I post new riding tips, subscribe by clicking the "follow" button (upper right). :thumbsup: