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About Rocket416

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  1. I have many years of experience on the YZ125 and below is my recommendation for gearing. 13-48 is the best gearing to run if your track conditions and motor allow you to pull it without too much clutch abuse. It allows the gears to pull longer and effectively make a bigger sweet spot in the rev range. 13-49 is the best gearing for the vast majority of riders. Allows you to use third gear in some corners and second gear in all but the tightest corners. Even in the really tight corners you can use second gear with some clutch abuse. This is my current gearing of choice due to my local track conditions. 13-50 is my least favorite gearing. Way too much shifting and the power range is very short. Some folks like this gearing but for me it was not good. Makes the bike very responsive but to me it was not going anywhere, just making a lot of noise. FYI.... All of this gearing was on a couple of full mod YZ125’s over the course of 150 plus hours, I weigh 175-185 and ride at an intermediate pace.
  2. I have ran about 50 gallons of Avgas 100LL and 927 mixed at 32-1 in my YZ125 without any separation. Just recently switched to Motul 800 and don't have any problems with that one either. Temperatures from 45 degrees to 100 degrees.
  3. Here is an example of the spark plug reading method mentioned in the above post. You just cut off the threaded portion to expose the carbon ring.
  4. I would try contacting James Saylor at JMS to see what he thinks. He has always been super helpful with anything I needed.
  5. The 2002 YZ125 was a great bike. I bought mine new and raced it to well over 100 hours. The only mod I did to mine was a two teeth larger rear sprocket. This was a MXA mag hot tip for that model. Can't remember what the factory tooth count was. That bike was faster than the same model CR, KX, etc. When others would ride my bike they were blown away that it was so much faster than their bikes. Used to pull holeshots more often than not.
  6. Richer jetting isn't going to solve your problem. You need a higher octane fuel. Your jetting is already on the rich side. Do do you know if that is the stock head or has it been machined for higher compression?
  7. If the seal would have been damaged it would have been leaking oil prior to it crapping out. The seal was damaged when the ball bearings pushed it out. I wish this was a very rare incident but the below thread points otherwise..... http://www.vitalmx.com/forums/Race-Shop,42/YZ125-case-repaired-Common-problem,1301169
  8. Yes, I'm sure I had the proper chain tension. I don't rely on the 3 finger rule ever since I cracked a rear hub way back in 2002. Since then I measure the chain tension and always give it an extra 1/8" slack for wet conditions in the morning and dirt accumulation. I remove the rear shock when I get a new bike, travel the swingarm until it reaches full tension and then mark my square. On this bike you should have about 2.375 inches from the swingarm to the bottom of the chain. This is not a chain tension issue, it's a weak bearing issue. There are a ton of guys with this same problem. There is a thread on VitalMX about this.
  9. Well I just got added to the list. 2016 YZ125 with 25 hours on the meter since new. Countershaft Bearing just let go and took out the cases and spit ball bearings into the tranny. Don't know what other damage this caused until I get it opened up. Chain was properly adjusted, oil changed every other ride (3 hours), properly filled with 660cc of oil, etc. This doesn't look like an isolated incident. Thing that has me worried is if I fix it with OEM parts what's to say this doesn't happen in another 25 hours? Has Yamaha updated this bearing with a new spec? This is my 2nd new YZ125 in the last couple years. My 2014 had 100+ hours with no transmission issues whatsoever.
  10. One thing that should not be overlooked is that stock bikes to mod bikes make a big difference on exhaust systems. If you are porting the cylinder you need to see what exhaust the tuner doing the work recommends. If that tuner has done his homework he should have tailored his work around a particular exhaust to get the biggest gains.
  11. If you don't mind post up some pics of the head now that you have it all cleaned up. And also pull the plug after you put a few hours on it to see how it's running. Should look similar to this if your jetting is close.
  12. The pics are not very clear but it appears you have some detonation going on and the head is pitted in the squish band on the exhaust side. If that is the case you need to run higher octane fuel, retard the timing, or get the squish clearance reduced to about .045". Any of those or a combination of the three will get rid of the detonation. Also if that piston has 23 hours on it I don't want to run whatever oil and ratio you are using. That piston has a lot of skirt wear and blow by. See below pics of a 20 hour YZ125 piston. These were 20 really hard hours on a deeply tilled MX track. Premix was Maxima 927 mixed at 32-1 with Avgas 100LL. As you can see a 20 hour piston should have very little to no wear visible.
  13. When I see guys running the stock pipe and shorty silencer I always get a good laugh. In my expierence on my YZ125's that set-up kills the over-rev/top end power. It's a 125 so that is where you should be riding. It might be a good woods set-up but not a good one for MX tracks. You will take a bike that has a short, narrow power band and make it smaller. Not good for me.
  14. Just as the others have said If your bike is in good condition, has proper jetting, good fuel, cylinder that isn't worn out, etc. you can expect about 100 trouble free hours before ever thinking about a crank or cylinder replate. Should just have to replace the piston every 30 to 50 hours depending on if it's a 125 or 250. I'm very hard on my bikes but very meticulous on my maintenance. Here is a piston I replaced yesterday on my 125. This is a 20 hour piston and as you can see it shows zero wear. Could have gone much longer. It's all in how you maintain them. I don't cut my bike any slack and I'm over 200 lbs with gear. These YZ's are bulletproof.
  15. In my YZ125 which is jetted a little richer than stock, 927 runs very clean. I'm running 32-1 and straight Avgas 100LL. If you run the bike hard enough and your jetting is in the ballpark you will not have any more spooge than other oils. I choose 927 since it is recommended by some of the sports top tuners and comes at a cheaper price point than the newer synthetics. This is a pic of my silencer after this weekends Moto's.
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