TTR125 gearbox noise

[robertlw]

I just bought an 05 Scorpa SY175F that has the bored out TTR125 Yam engine, no e-start, and magura hydro clutch. It is in very good shape and well maintained, original trials tires still like new. Yesterday the kickstarter kicked back hard against my boot, then a strange knock,rub,peck noise. It speeds up with engine and slows down at idle. Its not in rythym with the engine, but slower like a geartooth on a very large gear every revolution. It does it in neutral, riding slow, with or without clutch pulled in, in gear or out. I pulled the clutch cover and clutch, closely inspected the starter idle gear and the big gear behind clutch basket and all other visible gears. nothing visual could be found. Found a few very small metal chips in the oil screen. Used a magnet thru the holes inside the transmission. No chips. Checked the timing chain and upper sprocket, looks normal. The little bike runs great, no smoke. The noise sounds like inside transmission or behind clutch.Lower end in other words. Anybody know what this could be? I really was not planning to split the case on my newfound treasure the first week!

[Hawker]

I can only guess by your post. Take the cover off and remove the whole kick start assemble and check that there is no play in the end of the countershaft. Thats the shaft the idler gear rides on. And they sometimes break. The other thing is that mabey the kickstarter spring broke. I installed and kickstarter wrong one time I wound the spring the wrong way and it would kick back all the time.

good luck

[Olalla7700]

The same noise was created by my son when he piled the chain up against the case - but since you didn't have that issue - I don't think it was a sheared gear... that's what ended up being the culprit in his case. The first gear pinion and drive shaft were missing teeth, as well as a damaged second gear pinion. So, yeah, I've split the case on the TTR.

We've also had the dreaded kick stop - that was caused by a kick idler's bad circlip. We replaced it, but it still would occasionally clank and stall when the bike was running. Eventually we modified the kick shaft gear by grinding a chamfer... it was just weird, the spring was wound in the right direction and it was tight, the circlips were brand new - the shaft did not show any sign of being out of tolerance, but it would still occasionally cause the clank and stall the bike.

Hope you track down the issue without splitting the case.

-Kerry

[robertlw]

Latest report, flogged the trials bike pretty good yesterday, then drained the oil. No metal chips. Took off flywheel cover, everything looks normal at the stator. Upper cam sprocket looks fine. Ran the bike with the cam cover off, listened for noises. backed off the camchain tensioner and let it back, no difference. The noise is definetly coming from either behind clutch or farther back. I took out the whole clutch basket and kickstat assembly. Nothing really visible. Kickstarter idler gear and big gear on clutch basket looks fine. There is one thing we could not figure out though! Between the outer clutch basket and the inner hub, there is a spacer/bushing made from hard steel and has the star splines on the inside hole to slide over that input shaft. After sliding it over the splines, it reaches its final destination against the clutch basket, where it has no splines and is real loose on that part of the shaft. Just weird. The clutch works fine. I sorta think the knocking may not be in the transmission because it don`t matter if it`s in neutral idling, in gear with clutch pulled in, riding the bike with clutch out. The timing of the noise is much slower than the revolutions of the engine. Don`t you guys think the only gear large enough to make noise at a much slower pace than the engine almost has to be the very large gear behind the clutch basket? Idling in neutral, none of the transmission gears should even be turning? May just ride it til the noise gets louder, or metal chips appear in oil. The noise gets quieter the hotter the bike gets. thanks, Robert

I can only guess by your post. Take the cover off and remove the whole kick start assemble and check that there is no play in the end of the countershaft. Thats the shaft the idler gear rides on. And they sometimes break. The other thing is that mabey the kickstarter spring broke. I installed and kickstarter wrong one time I wound the spring the wrong way and it would kick back all the time.

good luck

The same noise was created by my son when he piled the chain up against the case - but since you didn't have that issue - I don't think it was a sheared gear... that's what ended up being the culprit in his case. The first gear pinion and drive shaft were missing teeth, as well as a damaged second gear pinion. So, yeah, I've split the case on the TTR.

We've also had the dreaded kick stop - that was caused by a kick idler's bad circlip. We replaced it, but it still would occasionally clank and stall when the bike was running. Eventually we modified the kick shaft gear by grinding a chamfer... it was just weird, the spring was wound in the right direction and it was tight, the circlips were brand new - the shaft did not show any sign of being out of tolerance, but it would still occasionally cause the clank and stall the bike.

Hope you track down the issue without splitting the case.

-Kerry

[Olalla7700]

With the bike in neutral and the clutch lever not engaged the pinion shaft side of the gear set can still turn within the transmission. This gear set is on the same shaft as the clutch basket and its gear, just within the case halves - your clutch cable/actuator ties through this shaft from one side of the engine to the other as it is hollow and accepts the clutch push rod set up. In neutral and clutch lever out, you have a set of gears spinning within the transmission -regardless. What causes the bike to stand still is the final drive gears and the pinions are all in position not to allow a transfer of rotation between them - in other words the shift barrel has aligned the shift forks to push/pull the gear sets into a position so you don't have any transfer of power from the top end to the output/counter shaft.

As far as your transmission spinning while the clutch lever is engaged, the forum has had a discussion about whether the output/counter shaft should spin if the rear wheel is off the ground and clutch is engaged - the answer is yes. The reason I bring this up is even with the clutch lever engaged and your transmission is in neutral the oil viscosity and engine vibration may make enough rotational energy to cause the pinion shaft to rotate within the case. So, even with the clutch lever engaged you may get a clanking with a broken tooth floating in the transmission.

If you have a gear tooth floating it may be stuck above the transmission gears with no way down, which was the case when we checked the first time to find the noise, it'll make a ting as it hits a gear. Eventually it made its way to the lower half of the case and we found it. When I split the cases I found two more broken off in the transmission. The teeth had also damaged the second gear.

The method for retaining the cutch basket is odd, but when you reinstall the clutch linkage, this is what gives the clutch some of it's "play" internal to the clutch basket. By removing the clutch springs and the push rod it seems as though there is more play than there should be.

The kick idler issue that most people speak of seems to be related to engine performance mods, as all people that post here with the issue seem to have a big bore kit installed. That problem, though, is apprent if you've already removed the clutch basket - the idler pretty much should have fallen out with the basket - the shaft usually shears at the case on the clutch side. If it was a kick idler within the case, that's the main/counter shaft.

I have a theory that the kick gear walks for some reason having to do with removal of the gear at some point in the engine rebuilding process. The idler collides with it while the engine is running and it shears the shaft... you'll see the nicks in the kick gear if the gears have been hitting at odd angles while the engine's at speed.

Other than splitting the case if not a kick idler, assuming you've gone over the flywheel and clutch cover areas, I am at a loss.

-Kerry