Space behind primary?

[Doc Harley]

Soupy, I'm glad for you to be moving forward. If Tarzan is correct, be prepared to accept some responsibility to get the necessary repairs made so you can end this season on a high note. Good luck!

 

[Stubbs]

My dealer has a theory that ever since YAM went to this stub shaft, lots of noisy clutches and belt life became an issue...It has not had this stub shaft for that long.

Dan

I’m pretty sure the stub shaft goes all the way back to original carbed 973 triple found in the Vector/Rage Dan, although I think the “fit” of the splines is a little higher on the tolerance side now. This would help explain why the clutch noise seems even more pronounced than ever.

 

[Tarzan]

Before we are too harsh on this design - all the 1049's are constructed this way as well as the new 998's for the SW.
I have overhauled this 'shaft assembly' and that bearing and shaft are pressed to together with considerable force. For the number of them out there, not many have caused issues like described.
MS

Its not the shaft thats moves on the bearing,its the bearing thats moves on the bearing house and the shaft and the bearing moves closer to the crank.

 

[Tarzan]

I’m pretty sure the stub shaft goes all the way back to original carbed 973 triple found in the Vector/Rage Dan, although I think the “fit” of the splines is a little higher on the tolerance side now. This would help explain why the clutch noise seems even more pronounced than ever.

I have drilled a hole tru the crank shaft into the oil-channel ,and mounted a plug that Yamaha sells into the drilled hole. The plug is cut a little bit so oil comes out of the crank and into the spline/stubshaft and the noice from the shaft is almost gone. Just a little bit noice left from the clutch weights. I have run the engine now for 4 seson with 1,9bar turbo pressure like this

 

[XP123]

This is a 1200 Doo engine and it looks like the same design. The poster claimed that the bearing on the end kept pushing inward. What is up with these three cylinder 4 strokes?

 

[Stubbs]

This is a 1200 Doo engine and it looks like the same design. The poster claimed that the bearing on the end kept pushing inward. What is up with these three cylinder 4 strokes?

Does BRP use this engine in other applications? I’ve always figured the OEM’s go this route to make the basic case design adaptable to other applications with a simple change in this assembly bolted to the end of the engine’s cases.

 

[jaydaniels]

I believe the reason for the stub shaft is to eliminate any axial force to the crankshaft. The primary clutch can apply side force to the crank and the 4 stoke crank isn’t designed to take this load. Stub shaft wasn’t needed in the Apex as the clutch wasn’t mounted directly to crankshaft as there was a reduction gear.

 

[Beerman]

I'd wonder if that post has grown and is on the shaft further than it should be. And if that post has grown, the movable would stick on the shaft when warm and bind not shifting properly because of tight bushing to shaft clearance. That WILL BLOW BELTS ALL DAY LONG and run super hot too!

That clutch needs to be warrantied!!! I think you have found the problem. Not that is sits closer to the engine, (it would however throw off the shimming) but IMO that shaft has to have expanded to sit on the shaft that much further and be binding on the movable bushing.

Mike, can you elaborate on this? I'm chasing my tail on my clutching, it's making heat with setups that no one else's does and not shifting all the all the way out. I have 2 SW primaries and both the moveable sheaves "stick" a little while fully open.

 

[ClutchMaster]

I believe KA is thinking it has slid on the taper therefore expanding the clutch shaft. It would affect offset a lot tho.

 

[KnappAttack]

Mike, can you elaborate on this? I'm chasing my tail on my clutching, it's making heat with setups that no one else's does and not shifting all the all the way out. I have 2 SW primaries and both the moveable sheaves "stick" a little while fully open.

Art,
The movable bushing needs about 7-8 thou clearance min. because as the clutch heats up, the clearance will close up and bind the bushing on the shaft making the movable stick. I've seen bushings pull right out before.

If the movable is sticking it can only be the bushing to shaft clearance, (possibly gummed up with rubber or belt debris or dust too) or from too tight tower to button clearance also.

 

[ClutchMaster]

My old primary with 2000 miles would stick a little when fully closed I never blew a belt at top speed .007” is worn out IMO, but don’t take my word for it look up the service limit.
I make my own bronze bushings and pressed in they have .002” clearance.

 

[ROCKERDAN]

I’m pretty sure the stub shaft goes all the way back to original carbed 973 triple found in the Vector/Rage Dan, although I think the “fit” of the splines is a little higher on the tolerance side now. This would help explain why the clutch noise seems even more pronounced than ever.

My dealer talked about a change in 15 I think it was? I know he said it was some change the same yr the vipers had the rod or crank recall thing. Maybe he will chime in. But that was when something was changed to make the new engine easy to be used in other power sports.

 

[ClutchMaster]

That primary looks like it should be a warranty replacement.

Did you ever try taking the clutch guard off, and then running the sled on a stand to make sure the belt is running true.

My brothers viper used to blow belts and have hot clutches, we had to machine 60 thou I believe off the back of the secondary clutch to get it in spec. Someone else had to do the same with their sidewinder I believe too.

Having to machine the secondary to achieve proper offset might be a sign that your bearings have moved.
I guess now that we know it does happen we will have to double check offset after every belt failure. Not such a big deal until it actually moves when your 100 miles from home.
Sorry for getting so pissed about all this, I just feel this is due to a bad design. Plenty of ways to prevent this other than just press fitting to hold it. Housing should have a internal snap ring installed. M2C

 

[ClutchMaster]

Unfortunately yamaha has no specification on wear limit for the primary sheave bushing. Skidoo recommends .0025”~003” clearance.
Calculated expansion of a 41mm solid steel shaft from 77 degrees fahrenheit to 300 degrees is approximately .001”
Remember that as the sheave gets hot (usually hotter than the shaft) the bushing I.D. will also get larger.

 

[**sj**]

also...theres a possibility over torquing could swedge the pin...weve seen this with the cats...

in the off season I will clearance mine minimally for smoother operation