Jump to content
Sign in to follow this  

Broken trans?

Recommended Posts

I did a quick search and didn't really find what I was looking for.

Yesterday:

I've got a 96 yz125 and it just recently flipped out on me. I was putting around my yard after lowering the needle in the carb. I was pulling the bike into my garage and put it on the stand(still running) and turned the gas off. I was gonna let it run the gas out of the bowl so i just let it idle. Now I know that the rpms raise a little when about to run out of gas, but my bike went full throttle. I hit the kill switch and it didn't work, I opened and closed the throttle in case the cable was hung up, still nothing. I waiting a moment to see if it would run out of fuel, but it was really making me nervous screaming at full throttle. I jumped on it and mashed the rear brake and jammed it into first gear. I immediately fired it back up, and it idled fine, and the kill switch worked fine.

Fast forward to today, and I crank it up and put it into first and putt around the yard again. I notice that it was making an awful clank noise when I let the clutch out. I pulled the clutch cover off and everything seemed to look okay. I pulled the chain off and ran through the gears( with the bike on the stand) and it made no noise. So I guess it has to have a load to cause it.

I really don't wanna split the cases, but I fear I must. Any ideas what could be it?

Share this post


Link to post
Share on other sites

Could have bent a shift fork, or done hard part damage. You can drain it and flush it to see if any parts fall out, but it sounds like you are gonna have to pop the seal

Share this post


Link to post
Share on other sites

Ok, finally started tearing into the yz. I noticed this noise after I pulled the clutch halfway out. The trans is in neutral and there seems to be a lot of slack in this motion. The clunk happens when it runs out of slack and I reverse direction of the sprocket. Any more thoughts as to what this could be before I split the cases?

th_VIDEO0002.jpg

Share this post


Link to post
Share on other sites

Wow, that sucks. Why did you want to drain your carb like that? It causes your bike to run super lean, and then the killswitch don't work because it don't even need spark to ignight when it is pinned like that.

Share this post


Link to post
Share on other sites

I've always drained my carb like that. The rpms usually pick up a little, but never went WOT. I don't ride this bike every weekend, sometimes it could be months before I ride it, so I like to run the fuel out of the bowl so it doesn't gum up the carb. After a while, the ethonal in the gas nowadays turns to goo.

Share this post


Link to post
Share on other sites

Having been through this years ago (bike sitting a while, didn't want fuel in it) I went to the problem of draining the tank after each use, even had a setup with an extra length of fuel line and a special cap for the gas can that the line plugged into. I don't think the amount left in the bowl would be that big of a problem, as it has the oil in it.

I do believe that leaving gas for high performance engines in plastic containers, fuel tanks, gas cans, etc, is a really bad practice and will get you 75 octane gas after about a week or so. The goodies they put in gas to make it high octane migrate right through the plastic, leaving only low grade petroleum residue behind. I have all of my gas in steel containers, some I've had for years. It seems to be good for about three months in the steel ones. I only mix up the amount of pre-mix I need, otherwise the can for the weed wacker gets more and more full. I used to have a lawn Boy 2 stroke mower where some of it could go, but no longer. Any pre-mix over about two weeks old is suspect.

The engines in the YZs and similar high performance two strokes have a lot more than listed compression ratio in reality: when the pipe and reeds are at full sync, you almost get a supercharging effect from the sonic action in the intake and exhaust system. So you are probably getting about 12-14:1 compression under those conditions. So crap gas doesn't cut it. Sorry for the wordy post, I read too much Gordon Jennings as a kid.

I wouldn't sweat the gas in the bowl if you use it more than once a month. If it bothers you, pull the jet access cap and drain it onto a rag. But I wouldn't store any gas in the tank if it sits for prolonged periods of time.

Share this post


Link to post
Share on other sites
Ok, finally started tearing into the yz. I noticed this noise after I pulled the clutch halfway out. The trans is in neutral and there seems to be a lot of slack in this motion. The clunk happens when it runs out of slack and I reverse direction of the sprocket. Any more thoughts as to what this could be before I split the cases?

First up: the "play" you feel there on that movie is normal: it is the amount of "freewheel" for lack of better term that comes from the engagement areas of the transmission. That isn't a problem. Every gear should have the same amount, or very close. They are all like that. If you don't believe me, go find a guy with a street bike that has a center stand: put it on the stand, put in in gear, and grab the back wheel: you'll get anywhere from 5 to 10 degrees of wheel rotation. I just tried it with my road bike: easily that much in first gear.

Next: Do you have any play the shock absorbing part of the clutch basket? You were holding onto the clutch hub, not the basket. Should have no motion that you can feel between the two. Really check that clutch basket. If you keep the spark plug in, try and rotate the clutch basket and see if it moves a lot before the crankshaft starts to turn. Should have a very small amount of rotation, but only as much as it takes to load the cushion system. Certainly not clunk-clunk back and forth.

Before I spilt the cases, I would do this:

Turn the trans shaft and run through each gear, try and feel if anything is not smooth motion in each gear. Have someone hold front sprocket with a rag or something to provide resistance. Don't cut their fingers off. The Rube Goldberg setup is needed as you really can't tell any problems with transmission without some load/drag. That's why running it on the stand with the chain off didn't show anything. If there's a gear problem, you'll no doubt feel it this way. It has to be somewhere, nothing is nowhere.

But what you found in the movie isn't a problem.

Edited by Yamaguy55

Share this post


Link to post
Share on other sites

Thanks yamaguy. I will definitely try that when I get home after work. As for the gas in the bowl, my bike was in storage for about 10 months and the gas in the bowl had turned to syrup. Drained the tank and had to soak the carb in cleaner for 2 days to get the sticky stuff out of the carb. But I guess i'll be draining it the proper way from now on. Thanks again.

Share this post


Link to post
Share on other sites

Finally some answers! Luckily I can get individual gears. Too bad its about $55.

IMAG0073.jpg

Share this post


Link to post
Share on other sites

Teeth! We don't need no steekin' teeth. I like the crack better than the missing tooth. Actually, since you have it, it isn't missing, is it? Check to be sure you have no case cracks as well. Lots of ways, but easiest way and cheapest, it to completely degrease it, then put in a container of gas ( outside, so you don't blow yourself up) then pull out, wipe off. If cracks are there, gas will seep out. works surprisingly well. I doubt you have any, but you never know after that episode.

Of course, if you have access to dye penetrant or Magnaflux testing, use it instead!

Share this post


Link to post
Share on other sites

Don't forget new seals, Yamabond4, and fresh gaskets. While you're there, Check everything...no use going in twice. Check the shift forks: if one side is more obviously worn more than other, replace it. $55.00 is cheap, even adding gaskets and seals to it.

Again, do it right the first time saves greater expense and aggravation later. No one I know NEEDS more aggravation. I certainly don't. Let us know how it turns out.

Share this post


Link to post
Share on other sites

thanks for the advice. All the bearings feel good and I think the shift forks look okay. Time to do some shopping. Any favorite companies to source oem parts? A friend pointed me to service Honda(yamaha section). I was thinking of this moose kit with seals. http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=261919&store=&catId=110&productId=p261919&leafCatId=11006

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

  • Similar Content

    • By Lone Danger
      Ok so I'm looking for opinions from those who have been on yz125s and 150 exc/xcw's and maybe the ktm 200's exc/xcw's. You gotta be out there.
      Here's the deal...I'm 5'7" 165lbs. A couple years back I was looking for a small bike for my wife to learn on and for me to play around with and race. Could only afford one bike. I got a '09 ktm 105 sx. Once I got it sprung for my weight it was great. I have been top five consistently in my local harescrambles B class, believe it or not. Ya, you were not the only ones shocked. And did pretty good in the local mx races as well, junior class up here in Canada. Lack of power was sometimes an issue but I learned to deal with it and just scream, scream, scream!
      However my wife is a complete beginner and she is scared of it. I have since moved her to a 4 stroke.
      Just got a mint '01 yz15 mid summer. Like less than 200 hrs! I have absolutely loved it on the mx track. Suspension is perfect and I love the extra power. I had planned to set it up for woods/mx with a suspension revalve. However, did a harescramble race a month ago that was really technical. Granted I have not done anything to the suspension minus clickers, had too much psi in the tires (13 front and 15 rear) (yes I know that's wonkey, I only had time to get a heavy duty tube in the front and had a stock tube in back. Less psi in the back would have been instant pinch flat because its so rocky) and it was running rich. I had to scream the thing to keep it running and even changed a plug mid race. Well I'm sure you can guess but it was the worst experience I have ever had on a motorcycle. The more open sections I passed a lot of people but the tech sections required way more effort than I liked and the suspension beat the hell out of me!!! Like my knees, wrists, and shoulders were just done. (I was out there for three hours).
      So keep in mind that I just came off a 105sx with suspension mods (set up for woods/mx). I have no problem slipping clutch and shifting precisely, yatta yatta. (I don't think the 105 would have done well here either due to even less power, however...) I've been second guessing fixing this 125 up for woods ever since I rode a friends '09 ktm 250xcw. I rode it on a local mx track. The power was just so effortless and I was absolutely floored by how the suspension worked. I never thought that I could hit the woops that hard and clear every jump on the track on an xcw and feel THAT good! It felt a lot heavier though, and I think the price tag on these things are going to be a stretch.
      So here's my question. I want the lightness of a 125, but want to be able to race both woods and mx. How does a 150 exc/xcw ENGINE compare to an mx 125 engine? I love the 125 engine, but more low end would be usefull in tech areas. But if there is not a huge difference, I will probably just revalve the yz for woods and go tubless, etc. The 150exc's are so expensive and I hardly ever even see one for sale unless its brand new. I don't want the weight of a 200/250/300. I barely touch the ground on a 125....so it has to at least be light. Is it worth waiting for a 150 engine? Thanks guys.
       
       
    • By doolan
      Hi guys I have a 2018 yz250 looking at changing springs front and rear I'm 200 pound ride b class moto.
      Having problems choosing spring weights using the calculators as mx tech say I need .45 fork springs and 5.2 rear but racetech say .48kg forks and 5.8kg rear.
      What are other bigger guys
    • By YamahaYz1
      Hey TT, I know there's endless topics on YZ250/ two stroke tuning in general but I have not been able to find one that helps me get my 09 YZ250 set up for my riding style and where I ride so I'm here asking for help. I got this bike around 1.5 years ago and have not known how to set it up properly. I know no one can give me a perfect set up but I'd like a good starting setup to work from and tweak to perfection. Throughout this time I've had this bike, its always been covering the bottom of the entire silencer and dripping all over the swing arm and rims with oil. Also, the joint between silencer and expansion pipe has oil around it too but I've heard I have to close the gap a little to squeeze the silencer a little tighter and stop the leakage there. I don't have too much experience messing with carbs but I've messed around with previous two strokes and tuned them a little better. I change the oil on my bike after 15-20 hours on it and clean and oil the air filter after almost every ride. The sparkplugs never last me more than a few months but recently have been lasting me no more than a few weeks. With the excess oil from the pipe and spark plug fouling you can see why I need to set my bike up to stop this. 
      The bike:
      Completely stock with V-Force 3 Reeds and a FMF Shorty silencer. 
      Usually running around 32:1 premix with 91 pump fuel because I prefer to keep it well lubricated instead of running rich.
      Riding:
      I ride enduro in Ontario, Canada. So mostly single track and some fire roads but nothing close to MX and not a lot of time wide open. Therefore, probably mostly 1/4-1/2 or 1/4-3/4 throttle range.
      Where I ride:
      Usually 0-500' above sea level. With temperatures ranging from around 15-35 degrees Celsius (55-95 Fahrenheit).
       
      If anyone can give me a setup to go from, that would be very much appreciated. Even multiple set ups for different temperature ranges or any suggestions would be much appreciated. Thanks and sorry for the long read, I just didn't want to leave anything out. Ask any questions if you have any, too.
    • By Goon Rides
      Hey guys... so I have a problem... I took the bike at Cal City, broke it in, and while I was doing so, the bike was bogging in first gear (Yes, first gear). Also it doesn't idle at all. I have to keep blipping it otherwise it'll stall. So I adjusted the screw circled in image 1. Well I was listening to the sound of the of the bike, yet the rpm's weren't increasing, and it was still stalling. So then, I unscrewed the screw in image 2, well I found out that it was fully twisted to the right. So then, I twisted it to the left, still nothing; it was still stalling... where's the idle screw? I am sure that the screw in image 1 is for the air/fuel mixture screw, and the screw in image 2 is the idle screw, just broken? I don't know, any and every help would be appreciated.


×