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Found 29 results

  1. Why|did|they|stop|making|XRs

    2 Stroke vs 4 Stroke

    Hey, Now this topic is all over the internet and I know theres no real answer, but I just wanted to hear your opinion do think 2 stroke or 4 stroke is better and why? Thanks
  2. 450pole

    2010 YZ450f Setup recommendations

    I am racing the Baja1000 for the first time this year on a team. All of the guys I am racing with have years of experience and have raced on teams and iron manned the race. Most of the guys I will be racing with have KTM or Hondas but I myself have the 2010 Yamaha YZ450F. I am looking for any recommendations on setting the bike for baja. I am an advanced rider, my style is somewhat aggressive, I weigh 180lbs and am 6'1. I am looking to maximize my fuel capacity, connect a light, kickstand, and tires. I am curious about gearing, and mapping for the bike as well as any other ideas you want to throw my way.
  3. Today I want to shift gears, open the floor for discussion, and talk about the state of dirt biking as it relates to the bikes we buy, ride, and maintain. In my relatively short existence, a number of things have happened in the industry which has been interesting to see. A few examples, which are not by any means exhaustive of all that has gone on, include the emergence of the four-stroke power plant, electronic fuel injection, improved tire technology, electric bikes, and the development of air forks. On a more micro-level we’ve seen improvements to materials, new manufacturing processes, and coating processes which have allowed ever increasing performance. As a fellow rider and someone who has no bias or stake when it comes to manufacturers and product offerings, I’d like to hear your thoughts as they relate to today’s machines. My question to you is a simple one, are your needs as a consumer being met by today’s manufacturers and bikes? What aspects of today’s machines do you love and what are pain points for you? If you could do things your way, what would you change? Are there machine variants that aren’t being offered? Leave a comment below that addresses these questions or share your historical perspective! I look forward to your responses. Thanks and have a great week! - Paul https://www.diymotofix.com/
  4. I have a chinese WildFire dirt bike 250 pro and i got the thing on new years day 2018 for $300 it ran but it wasnt healthy its a four stroke and just recently completely cleaned the carb and it runs but i have to physically pour gas down the cylinder to start it.. Its got electric start but it doesnt spark and only sparks when the bike is warmed up so the only way to start it is pour gas down the carb and kick it or use starter fluid in which i dont have nor do i want to use it.. I just need help right now i have a scheduled trail ride with my buddies in a few weeks so i really need this thing to start without pouring gas down the cylinder (i dont pour much at all) UPDATE: the intake tube from the carb to the engine was not screwed in all the way so i tightened the &%$#@! out of it and i kicked it and it started after 4 kicks (not too cold but its 35 degrees Fahrenheit out right now) thanks guys for the suggestions!!
  5. Hi, I recently bought a used 2014 Yz250f (efi bike) and i have been having a problem with it. So i bought the bike from a guy who raced motocross, he kept the bike in tip top shape. When i got the bike, it had a fresh top-end with a high compression piston, and stage two hotcams and a aftermarket exhaust systems. I race a mix of woods and moto races so i figured i could just add a few things for the woods and it would be set to go. When i was riding the bike before buying it, the seller mentioned that the bike almost "hesitates" when going from low to high rpms, he said that this had something to do with the new sprockets but to just stay on the gas. i bought the bike not thinking much about that because it was all around a really nice bike but now i cannot for the life of me figure out what is a causing that bog. On a moto track you hardly notice it because your always riding in the top end of the rpm range, however in the tight woods it makes the bike difficult the ride. It almost feels like there is a gap inbetween the bottom and top end powerwise, and you have to roll on the throttle real smooth in order for it to not sputter. If your going slow and then try and grab throttle quickly (to get over a log for example), it sputters out and there is no power. I tried giving the bike more bottom end power by adding a bigger sprocket, which gave more bottom end but didnt make the bog go away. Then i bought a GYTR Power Tuner, thinking i could retard the Ignition timing and move the power to the bottom end. I haven't gotten to test it a ton yet, but so far maps have helped take away the bog. Aside from that the bike runs perfectly, i have looked online and found no one else who seems to have had this problem which is why i am posting this. Any ideas would be greatly appreciated, as i have no clue what to do next, Thanks.
  6. Hey guys, I have a 2012 KX450f and it is giving me major issues. I will give you a run down of the history of it. I bought this bike a few months ago and have only ridden it really once, yes once! When I bought it everything seemed to check out, it ran fine, started fine, sounded fine, so I bought it. Took it out to ride and the first hill I hit it got really hot and overheated like a SOB and spewed coolant everywhere. I thought to my self maybe it was because we were riding trails slow before so maybe when I actually got on it it got too hot. After that though, it began to overheat every 3 minutes no matter what, I would ride it for 3 minutes, and have to stop to let it cool down because I was scared I was going to melt the top end. Got home and started inspecting, found out that oil and coolant was mixing both where the oil is supposed to be and where the coolant is supposed to be. After some research I found that the 2012 450 had head gasket issues. Assuming that was the issue, I took the head off and got it resurfaced (it was actually decently warped) and put new gaskets in everything top end related. Piston and cylinder looked brand new by the way. So I put it back together, started it up, and it instantly started spewing coolant and oil mixed out of the crank case breather hose. Like literally as soon as i started it and it would make a puddle on the ground in 10-15 seconds. I'm at a loss here, brand new coolant and brand new oil, brand new head gasket and resurfaced head, and it instantly started doing the same thing again? What could it be? Is it worth my time or do I part the bike out? I have put way too much time into this bike to want to tear back into it again unless it is something cheap to fix, if not I am going to post it on craigslist and let someone else deal with it. Overall this whole experience makes me want to go back to a 250T! XD
  7. MotoXRacer_19

    KTM 350 XC-F Reviews

    Hi Guys. I'm in the market for a different bike as mine isn't cutting it for me anymore. I have a 2010 KTM 250 XC and have the opportunity to buy a damn near brand new 2014 KTM 350 XC-F. I've heard a lot of mixed things about the 350, and was wondering what the owners of them have to say about them. I've read a lot about different years but haven't heard much of anything about the 2014. Can someone help me out?
  8. Anyone who could help would be a great help and im in the missouri area interested would be great too
  9. Paul Olesen

    Three Easy Ways to Improve Engine Cooling

    This month I want to discuss three easy ways to improve engine cooling for your dirt bike or ATV and explain why they are effective. As improvements are made to an engine that increase its power, the amount of heat the engine will create will also increase. Effectively removing heat from the engine and cooling it is very important as the power output of the engine goes up. The cooler an engine runs, the more power it can produce. There are three ways that the aftermarket attempts to improve the cooling system of a particular engine. 1. Increase flow through the cooling system. 2. Increase the cooling capacity of the radiators. 3. Increase the pressure of the cooling system. Let's dive in. 1. Increase flow through the cooling system The flow through the cooling system can be increased by installing a water pump impeller designed to increase the flow rate of the coolant. The reason increasing the flow rate of coolant works is because the rate of heat transfer from the engine to the cooling system is directly proportional to the mass flow rate of coolant. This is thermodynamics jargon, but there are two key parts to consider. First, how much coolant is flowing, and second, at what speed the coolant is flowing. The more coolant that flows and the faster it flows will reduce the temperature difference between the point where the coolant enters into the engine and where it exits. This next part is not quite as intuitive. When the temperature difference between the inlet and outlet is reduced, the average coolant temperature is lowered. When the average coolant temperature is lowered the engine will run cooler. This is why fitting a water pump, which increases the flow of coolant through the engine, improves cooling. 2. Increase the cooling capacity of the radiators Radiators consist of a series of tubes and fins which run from the top to the bottom of the radiator. These are often referred to as the radiator’s cores. As coolant enters the radiator it moves through the series of tubes and heat is transferred from the coolant to the fins. Air passes over the fins and heat is transferred from the fins to the air. This transfer of heat from coolant to air is how radiators reduce the temperature of the coolant. Coolant temperatures can be reduced by upgrading radiators in three ways, by increasing the frontal area of the radiators, by making the radiators thicker, or by using materials with better heat transfer properties for the cores. For all practical purposes, increasing the radiators’ frontal area and improving the core materials is rarely a viable option for dirt bike applications. This is because there is little room for the radiators to begin with and they are susceptible to damage, making the use of expensive core materials a risky affair. Unfortunately, both of these options are better improvements to make before resorting to increasing the thickness of the radiators. Increasing the thickness of a radiator is not as efficient of an improvement as increasing the frontal area of the radiator. In order for thicker radiators to cool more effectively than their stock counterparts, airflow past the radiators is key. When the thickness of a radiator is increased, air must travel a greater distance through the radiator before exiting. The speed the air is traveling plays a big role in determining how quickly the air heats up as it moves through the radiator. If the air is not traveling fast enough through the radiator, the air temperature will rise and equal the coolant temperature before reaching the end of the radiator. Once this happens, heat transfer stops and whatever portion of the radiator remains will not help with cooling. In order for a thicker radiator to be effective, air must flow quickly enough through it so that the exiting air temperature is at, or better yet, below the coolant temperature. In conclusion, benefits from adding thicker radiators will be more prominent in applications where speeds are relatively high. Whereas in applications where the bike is hardly moving, improved cooling may not be noticeable. 3. Increase the pressure of the cooling system The last alteration to the cooling system that can be made is to install a high pressure radiator cap. As coolant temperature increases, pressure increases inside the cooling system. The radiator cap is designed to be the pressure release point in the cooling system in the event that too much pressure builds up. This can occur as a result of overheating or a blown head gasket for example. By designing the radiator cap to be the weak link in the system, other parts of the system, such as seals, don’t end up getting damaged from being over pressurized. The radiator cap features a plug and spring on its underside. The spring is designed to compress once a certain pressure is reached, at which point the plug will move upwards and uncover a pressure release hole where excess pressure will be vented. The coolant’s boiling point and ability to conduct heat are necessary factors in understanding why a high pressure radiator cap can help improve engine cooling. Water alone boils at 212°F (100°C) while a 50/50 mix of water and antifreeze boils at 223°F (106.1C). Radiator cap pressure designations are usually advertised in bar, with most stock radiator caps designed to withstand pressures up to 1.1 bar (16psi). The more pressure a fluid is under, the more difficult it becomes for the fluid to vaporize, and the higher its boiling point becomes. When water is under 1.1 bar of pressure, the temperature water will boil at is 260°F (127°C) while a 50/50 antifreeze mix will boil at 271°F (133°C). By installing a radiator cap designed to withstand higher pressures, an additional increase in the coolant’s boiling point will be seen. High pressure caps are usually designed to withstand 1.3 bar (19psi) of pressure. This 0.2 bar (3psi) increase in pressure over the stock system will increase the boiling point of water or antifreeze by 8.7°F (4.83°C). This will then bring the boiling point of pure water or a 50/50 antifreeze mix to approximately 269°F (132°C) and 280°F (138°C) respectively. While this small temperature increase alone won’t do a lot for your engine, coupling a high pressure cap and using coolants with better heat transfer properties can do wonders. Antifreeze (ethylene glycol) alone is not an inherently good conductor of heat. In fact, pure antifreeze conducts heat about half as well as water, while a 50/50 mix of antifreeze and water conducts heat approximately three quarters as efficiently as pure water. This means a cooling system using a 50/50 mix of antifreeze would have to flow faster than a cooling system filled with pure distilled water in order to achieve the same cooling efficiency. What this means for you is significant cooling gains can be made by using distilled water and an additive called “Water Wetter” in place of an antifreeze-water mix. Water Wetter is an additive that improves water’s “wetting” abilities (another whole subject), adds corrosion resistance, and slightly increases the boiling point of water. A high pressure radiator cap in conjunction with distilled water and Water Wetter as the coolant is by far the best route to go for high performance applications where freezing is not an issue. For applications which must still be resistant to freezing, the antifreeze-water ratio can be altered in favor of mixtures incorporating more water than antifreeze so that the cooling efficiency of the mixture is improved. Just bear in mind the freezing point of the mixture as it is thinned with water will be reduced, so you will need to pay close attention to the environment you are operating in so that the coolant is never susceptible to freezing. A frozen coolant system can ruin an engine and makes for a very bad day! I hope you enjoyed this post on three easy ways to improve your engine’s cooling. One more thing before I wrap up! April is Autism Awareness month, and here at DIY Moto Fix we couldn't be more excited to announce that we will be donating 15% of all profits made in April to AutismMX. If you haven't heard of AutismMX, this amazing non-profit brings Autism awareness to the motorcross community. Founder, Matthew Dalton, created this non-profit after finding that motorcross was an amazing way to connect with his autistic son. At DIY Moto Fix this non-profit also touches a chord with us. Our filmmaker and photographer, Kelsey Jorissen, loved dirt biking with her autistic brother throughout their childhood. The Autism MX Project focuses on four areas: Autism MX Day Camps are days for ASD kids and families to have the chance to ride AMX’s little dirt bikes and quads and enjoy the sport of motocross. Team Autism MX Sponsoring amateur MX racers, riders as well as sponsoring AMA pro racers. Through doing so, they are getting out the word on Autism Awareness to millions. AMX Puzzle Piece Apparel from shirts, graphics, goggles, to help stand out and support Autism Awareness. AMX Ride Days for Autism Awareness AMX celebrates Autism Awareness and is a fundraiser for The Autism MX Project. So for the entire month of April - if you buy a book, a video, even a poster - 15% of that purchase will go towards AutismMX and their amazing cause. Thanks for reading and have a great rest of your week!
  10. I had a disastrous oil change today. I only drained out one of my drain bolts (the one on the back right side of the engine) at first. After draining that one bolt, I put 1 and 1/4 quarts of oil in the bike. And then, "OH CRAP!" I realized I had only drained that reservoir.... I thought maybe if I drained one bolt it would also drain most of the other? But I wasn't taking any chances so I drained out both bolts this time and started over. I then put 1 and 1/4 quarts back in and finished up. I checked the oil level window, and it looks like the oil goes over the window? This bike has no dipstick which sucks. I took the bike for a 10 minute ride and stopped and held it upright and it still looked like it was over the window. Where is the level supposed to be? Is it supposed to be over the window? I don't think I put too much, if I did please let me know. I ALSO CHANGED THE OIL FILTER. Thanks!
  11. I'm and intermediate rider who rides very aggressively and on hard, but fast-paced woods/cross-country/harescramble riding. Sometimes I'll do technical, really tight trails, log crossings, and hillclimbs, etc. and I also will ride motocross tracks every once in a while. I currently own a 2008 KTM 250 XC-F with a bigger rear sprocket, FMF exhaust, aftermarket piston, and I typically run high octane fuel. I won't be upgrading for quite a while but I am planning ahead trying to decide what to save up for and all that. I'm sure this forum will also help others in similar situations. I'd like something that can top out faster than my bike but something that can accelerate quickly and have more torque as well. The majority of my riding is very fast-paced woods with hard corners and lots of roots and steep hills as well, so I'd like something that can blow through corners and accelerate quickly. But, I also ride a lot of tight technical trails so I'd like something that's torquey and has explosive, yet controllable power and something I can take over big logs and rocks. I'm fine with a bike that likes to be revved a lot as that's what I do on my 250xcf now. I'm used to four strokes although I'll probably adjust to a two stroke very quickly as I ride constantly. I'm leaning towards a 250 XC or a 350 XC-F although I've heard lots about KTM's 125 and 150 2 strokes, the 450 and 500, the wide ratio "w" models of the cross country bikes, and their respective motocross models just because I know how explosive they are. I understand that this is a lot to ask out of one bike but I'm going to be adding a lot of aftermarket parts to whatever I end up getting if it doesn't already have any. Tell me all about these bikes if any of you guys have ridden them! I'm probably going KTM because I've heard nothing but good things about them but I will still consider any other brands as well. Tell me any aftermarket you had to do, improvements to be done or downfalls of each bike, and all their advantages and things they're better at than the other ones if you've ridden more than one of these. This is more of a harescramble/cross-country racing post, but since some of my races have parts of motocross tracks I'd like to hear how they do on the track. Also, money isn't too huge of a concern with me but I will definitely not be able to get a brand new bike. I will be racing so if it's bigger than a 250 then I'll have to be sure that it can compete with bigger bikes. Thanks, in advance!
  12. Paul Olesen

    Checking and Setting Cam Timing

    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
  13. Paul Olesen

    How to Separate Your Crankcases The Right Way

    “Splitting the cases” is often referred to as a daunting or undesirable task, but if you are well prepared and properly equipped then it can be a straightforward job. To alleviate any concerns you may have with the task, I want to discuss best practices and share some tips that you may find useful when dealing with crank bearings that utilize an interference fit with the crankshaft. We’ll get started by discussing preparatory items and work through to completing the job. Preparation I always recommend prepping for crankcase separation by thoroughly reviewing the service manual. This is important in case any special instructions are present, such as guidance on how the crankcases should be positioned. Typically, it is advantageous to lift one half off the other in a certain orientation due to the way the gearbox or other components are installed. Secondly, a review of the manual may highlight any specific hardware that must be removed prior to attempting to split the cases. From a tools standpoint, a crankcase splitter tool is a worthy investment because it will help ensure the job goes smoothly. Case splitters are relatively inexpensive and widely available. Alternatively, for the budget conscious or lesser prepared, a case splitter is something that could be fabricated. Whether buying or making, ensure you pick up a model with a protective end cap for the crankshaft or fabricate one. We’ll discuss the end cap later. The other tools required are all fairly standard and include your typical sockets, wrenches, and soft mallets. Wooden blocks or other soft semi-malleable spacers should be selected which level and raise the crankcases off the tabletop. This allows the cases to be positioned so that the split line between the cases lies horizontally and subsequent splitting can be done vertically. This will help ensure evenness of separation as well as reduce the likelihood of components falling out of the cases unexpectedly. As much as shortcuts are desirable, just about everything external to the cases must be removed in order to successfully split the cases. Clutch, stator, crank gear, etc. must be removed prior to case splitting. Your service manual will provide further clarity as to what needs to come off. Technique & Tips Once you’re ready to separate the cases, the first thing we’ll need to do is remove all the crankcase bolts. The crankcase bolts should be removed via any prescribed patterns outlined in the service manual. Since the crankcase bolts are typically several different lengths, ensuring the location of each bolt is well documented is extremely important. As I discussed in my post on keeping track of bolts, the cardboard gasket method or any other you find suitable should be utilized so that the reassembly process is straightforward later on. After the crankcase bolts have been removed, the crankcases should be inspected one final time to ensure no hardware that should have been removed prior is hitchhiking. Trust me, trying to separate cases only to find there is one last forgotten bolt is quite frustrating! Once you’re confident all the necessary hardware has been removed, position the cases on the blocks with the correct half facing up. Next, install the protective cap over the crankshaft. I advise using the cap whether you own a two or four-stroke simply because in both cases it helps preserve the end of the crankshaft. This is of particular importance on four-stroke engines that utilize an oil feed that passes through the crank. Once the crank end is protected, proceed to install the crankcase splitter. Select threaded holes that are as close to equispaced from one another as possible to promote uniform loading of the case splitter. When threading the case splitter studs into the crankcase, make sure you engage at least 1.5 times the diameter of the stud diameter. For example, if the stud is 6mm in diameter make sure at least 9mm of thread engagement length is achieved. This will help ensure the threads are not stripped when you attempt to separate the crankcases. With the crankcase splitter installed begin tensioning the main bolt against the end of the protective cap. Proceed to tighten the bolt until the crankcases begin to separate about a 1/16” (1.5mm). Once separation has occurred, make sure that separation is even all the way around the cases. Due to the way the case splitter loads the cases, the area near the output sprocket tends to lag. Case separation needs to be even so that the dowel pins used to pair the cases together don’t bind. If the output sprocket end of the cases hasn’t separated, use a soft rubber or plastic mallet to gently tap in that area. Tap carefully and only on case areas that appear sturdy. Once you’ve created an even gap, proceed to tension the splitter bolt, tap when necessary, and fully remove the crankcase. Upon separation, make sure that no gearbox components, such as washers, have stuck to the case. What I’ve described is the ideal sequence of events for a successful case separation, however, occasionally the cases won’t be as cooperative. In the past, I’ve had to deal with crankcases where moisture has found its way into the dowel pin bores and corroded the dowel pins. This effectively seizes the dowel pins in their bores and makes the separation job more challenging. If the crankcases are being resilient to separation, stuck dowel pins may be a potential problem. Most dowel pins are located opposite one another and their exact position can often be referenced in the service manual or in the crankcase section of part microfiches. Once the location of the dowel pins has been confirmed, a torch can be used to lightly heat the dowel pin areas. Heat will expand the metal surrounding the dowel pin and aid in freeing up the stuck pin bore. Usually, a few careful rounds of heat, tension on the splitter, and well-placed tapping is enough to free up the pesky cases and get them separated. Alternatively, if the heat does not help, applying a penetrant to the pin bore areas is another option that may help free things up. If you find yourself dealing with stuck cases, the key is to be patient and think through all your options. In these types of situations, most mistakes are avoidable and are usually the result of rushed decisions. Once the cases have been separated, the remaining tasks of removing the gearbox and pushing the crank out of the remaining case half can commence. I hope you’ve enjoyed this write up on crankcase separation and that it makes you more prepared for the job. If you’ve got additional crankcase separation tips that you want to share, please leave a comment below. For additional engine building information, whether two or four-stroke, check out my engine building handbooks. Each handbook is offered in print or digital form, contains over 250 color pictures, detailed instruction from start to finish on full rebuilds, and contains a wealth of information pertaining to diagnostic testing and precision measuring. Thanks and have a great week! -Paul
  14. MotoXRacer_19

    AMA Numbers

    Does anyone know how to, or if you can, change your AMA number? The race number, not the full thing.
  15. frontline510

    Need help with Timing

    Hello everyone, I am currently rebuilding my top end on my 2001 Wr250f. Everything has been going smoothly until it came time to set the cam timing. I have set the motor to tdc, and slipped both cams under the timing chain. No matter what I do, I cannot seem to align the camshaft timing marks level with the head of the motor. The exhaust side cam aligns perfectly with the dot sitting flush with the head line. The intake side cam mark always ends below the head line or above. Neither way looks natural. The dot is either too deep to the point I can't see it, or too high to the point it floats above the head line. Which way is correct? Thanks in advance for any input.
  16. throttle127

    Kx250f vs yz250f?!

    I was wondering which bike is better. I have heard many things about both bikes, good and bad. I will be using it for track and trails.
  17. In the past I've used foam air filter oils like uní oil and Yamalube's air filter oil, but Im bottles are dry. I still have some 2 stroke oil from my old bike, will it work just as fine for oiling the air filter? It's Yamalube 2-cycle oil. Thanks for any help you give me.
  18. So i never owned a fuel injected dirt bike, I got a 2016 yz450f for a steal at an auction. It ran great every kick since this last ride, it started dying when i wasn't on the throttle. I got it home and now the second i put the choke in it dies/ it runs/rides when im on throttle but if im not on the pipe it dies. I went check the valves all in spec, found a video how to flush fuel injector with a battery, flushed it still doesn't idle with choke in. Now im clueless what to do usually a problem like this I clean out the carb and that fixes the problem (get a fuel injected bike they say...) ha, I only run non ethanol fuel through all my machines. so what are my next steps? and is the upgraded ecu with the tuner worth the $? any specific tips/things to do to make sure thing runs like a top every time/ things to know when Im out in the field to trouble shoot a injector? thanks
  19. Hey guys I just bought a bike last night. So the seller said the bike will turn on but then die. We didn't try it because it was really late at night and it was raining (seat was wet). But he said if you bump start it, it will turn on and ride. So what do you think the problem is? I just want to make sure it runs... I probably won't be able to bump start it till Saturday (rain)... It's a four stroke, and I know absolutely nothing about them. Thanks.
  20. Paul Olesen

    Maintenance Readiness

    I hope you all have been out riding and enjoying spring. I got back into the hare scramble racing scene over the weekend after a three year hiatus and had a blast. Today, I just want to share a quick tip and start a discussion on preparatory things that help shorten the time it takes to do complex maintenance tasks, such as rebuilding an engine. Quick Tip Prior to turning a wrench carefully look over the service manual scanning through all the applicable procedures and subsystems. If I’m working on an unfamiliar model, I find it is helpful to jot down a rough outline of the disassembly sequence. This saves me time in the long run as I don’t have to rely as heavily on the service manual or continually flip through various sections. Another option is to use post-it notes to bookmark each relevant section in the manual. Mark the post-it notes with numbers or headings so you know where to turn to next. Earmarking or bookmarking the torque tables is also a huge time saver no matter the task. Be sure to scan through the manual as well to identify any specialty tools that are required that you may not have. Discussion Points What other preparatory things can be done to help speed up the major maintenance process? Is there a method to your madness or do you dive right in? Thanks for reading! Paul https://www.diymotofix.com/
  21. Daniel Wolfe

    Do i get a 06 CRF250

    So i've only owned 2 strokes and i now own a 01 KX250 that i've fully rebuilt from ground up and i've enjoyed my time on it even though it's been short i rebuilt it in november so not much riding on the old girl but i've been thinking about getting a honda 250 so i found a guy who wants to trade his 06 crf250 for my KX he says he's more of a kawi guy and wants a KX250 2 stroke to go with his kx yard thumper problem is A i don't know much about four strokes he says the bike has 20 hours on it since the previous rebuild is that a lot for a 4 stroke B i heard the 06 is a boggy valve eating &%$#@! with proper maintenance can this be avoided i know a lot of people neglect the bikes so i don't know do any of you guys think this is a good deal or should i keep the kx and if there are any other known issues with this year 250 i should worry about or i just don't want to buy something i immediately have to throw a grand into
  22. Paul Olesen

    Four Stroke Cylinder Head Reconditioning

    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
  23. With warmer weather and the riding season around the corner for many of us, I wanted to cover a topic that can either make or break an event. Whether you’re competing in a racing series or traveling to the track or trail, let's talk about event preparedness. More specifically, what spare parts should you keep on hand? Plus, what methods do you use to keep your spares organized? Honestly, I struggled with organization until I started working on this post. I had no method to my madness. Every time an event came up I’d do the same thing; throw a bunch of stuff in a box or the back of my van and head to the event. The sad part is I now realize this was a weakness of mine for quite some time, but didn’t do anything about it! Maybe you can relate? I finally said enough is enough. I don’t throw my tools in a cardboard box when I go to a race, leaving what I bring to the fate of my memory. So why would I do that with the spare parts I bring? I started solving this problem by compiling a spreadsheet detailing what spare parts I keep on hand for ice racing and hare scrambles. I realize that each discipline will differ and may have niche parts that should be kept. The goal here is not to definitively define what spares one should keep on hand, but to have a conversation and provide a resource that can be used to help people get set up based on their own needs. Once I took inventory of everything I felt I wanted to bring to a race, I went to Menards and went hunting for the perfect organized storage bin/toolbox. Here’s what I ended up with: Naturally, once I returned with the toolbox, my list grew and I probably need to go back for a bigger one. I intend to store a copy of the spreadsheet in the tote so I can keep tabs on inventory and know exactly what I have available. Should I get another bike, this system is easily replicable and my plan is to get another organized toolbox that goes with it. This system is how I went from being an unorganized “throw it in the van at the last minute” rider to a more relaxed well prepared rider. I’d love to hear how you handle event readiness, what you bring, and how you keep track of it. My hope is that by sharing our strategies we’ll save someone the misfortune of having a bad day at the track or trail. Perhaps I'll even end up with more things I need to add to my list. -Paul If enjoyed this post be sure to follow my blog and sign up for my newsletter! DIY Moto Fix Newsletter
  24. Hi everyone, new to the forum seeking advice. I want to buy another bike. I've been riding a 2002 KTM 520 EXC and it's been a great bike but looking to upgrade to a newer 500 KTM or a 300 XCW. I ride mostly Northern California single track, double track, and occasionally fire roads. Having a plate is not a priority since I have a plated xr650. I'm 6'3'' and have always ridden big bore bikes, so bike weight hasn't been an issue....But I haven't ridden a 300 yet, and I hear they're awesome. Which model would you buy? Should I look at a Husky? If I buy used, what year range is best? Thanks!
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