Keep an eye on the STM billet secondary clutches for cracks...

[KnappAttack]

A public service announcement brought to you by Clutchmaster, who we haven seen here in a while, which really bums me out... He is a wealth of information!

Clutchmaster just purchased my Pro-4 secondary to replace his STM secondary that cracked. He sent me pics of cracks in the webbing on the STM.

It sounds as though that this is a reoccurring theme with the STM secondary. He mentioned STM claims the Yamaha "triple harmonics" are to blame. Clutchmaster said his STM secondary has only 3500 miles on it and has never blown a belt with it installed. He thinks the heat cycling, thin sheaves and thin webbing are to blame, for the cracking, not harmonics. He has run on the 270 tune 90% of the time for those 3500 miles.

He has the Pro-4 in his hands and has measured the webbing to be thicker on the Pro-4 along with the sheave thickness to be thicker, not to mention the Pro-4 has more webbing in it than the STM does too.

He googled the cracks on STM & there's also cracking reports on the 1100 Cat twins and Ski-Doo triples as well, so this appears to be a more common theme than just the Yamaha triple engines. Keep a close eye on them! Just because there billet, doesn't mean they won't crack.

 

[Hammer70]

Thanks knapp for the information I definitely will keep eye out.

 

[DooZ]

Welderup...
Seriously tho I'll be checking mine

 

[Upstater57]

Thank you for the update.

I think blaming harmonics damage on a clutch that not directly mounted to the engine is a smoke screen.

Looks like a TAPP clutch with a Pro 4 might be the best set up for big HP.

 

[max rolph]

Dave is working on a TAPP secoundary ... that would be nice... along with an alinement tool for each install!!!

 

[Upstater57]

Dave is working on a TAPP secoundary ... that would be nice... along with an alinement tool for each install!!!

I would sign up for a TAPP secondary with the alignment tool ! LOL

 

[Simplespeed]

Could these cracks be caused from Harmonic’s?? Yes its possible but in my opinion highly unlikely… The motor does have 60 degrees of wasted vibrating rotation that causes some unwanted harmonic’s at lower Rpm but goes away as soon as you start spinning over these area’s with some higher RPM where all major time ( use ) is spent .. The location of cracks are at the deepest thickest part of the webbing where the belt is at full shift out or very near 1 to 1 or even overdrive .. so is this the area where the most force is applied ??? lets look at it from 200 hp and 300 hp angle.. we know 300 is 50% more than 200 but what about force??? Their is 55,000 more force needed to make 300 horsepower vs 200 horsepower . in simple terms it takes enough force to move 165,000 pounds one foot to make 300 horsepower and 110,000 pounds one foot to make 200 horsepower.. Now how much of that force will be applied to a clutch system if the wrong spring, wrong helix, wrong tension, weak design, coil spring bind, busching bind, wrong off set, wrong center to center, bad raw metal when made and so on not to mention blown belts, clutch imbalance, and excessive heat all caused from above…. Thank You Mike for the post as STM should be figuring out a way to keep their customers and not so fast to blame other variables.. We now know its not bulletproof and crossed off the list…

 

[STAIN]

I have seen this in the past with STM secondaries on my buddies tuned 1100's. They both cracked. STM offers no support. One reason I dont buy STM stuff....

 

[SideHogger]

I had to replace a stock one that cracked also but I can’t remember precisely where on clutch. I’ll have to look tomorrow.

 

[Rtbo]

Found this early this year when I noticed I was missing a roller and another roller was cracked. Stock tune 9400 miles

 

[justinator]

Ive seen this before with the stms.......dont remember if it was on hcs or facebook but definetly saw it. Buddies brand new srx has a totaled belt guard, destroyed lower pan and side panel due to a 500 mile stm supertipweight breaking. Unfortunate to spend all that money on "top notch" stuff and have issues like this. The tapp stuff is nice quality but itll cost you 1/4 the cost of what you paid for your new sled to have a primary and the new secondary.

 

[stone88]

A public service announcement brought to you by Clutchmaster, who we haven seen here in a while, which really bums me out... He is a wealth of information!

Clutchmaster just purchased my Pro-4 secondary to replace his STM secondary that cracked. He sent me pics of cracks in the webbing on the STM.

It sounds as though that this is a reoccurring theme with the STM secondary. He mentioned STM claims the Yamaha "triple harmonics" are to blame. Clutchmaster said his STM secondary has only 3500 miles on it and has never blown a belt with it installed. He thinks the heat cycling, thin sheaves and thin webbing are to blame, for the cracking, not harmonics. He has run on the 270 tune 90% of the time for those 3500 miles.

He has the Pro-4 in his hands and has measured the webbing to be thicker on the Pro-4 along with the sheave thickness to be thicker, not to mention the Pro-4 has more webbing in it than the STM does too.

He googled the cracks on STM & there's also cracking reports on the 1100 Cat twins and Ski-Doo triples as well, so this appears to be a more common theme than just the Yamaha triple engines. Keep a close eye on them! Just because there billet, doesn't mean they won't crack.


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I don't buy the harmonics issue on the secondary its heat related guaranteed lots of slip even with a good set up its hard to mange 300 hp with the constant on and off of trail riding on a 2-300 mile day of riding especially when running beside another 300 hp sled all day. I had a stock secondary come apart on me a few years ago. Stm makes a great product thats why you see all the 600- 1000 hp sleds using them in the hypersports camp.

 

[Upstater57]

I don't think the hypersports guys ride their sleds for 200/300 mile rides holding them wide open for miles. LOL

 

[KnappAttack]

I don't buy the harmonics issue on the secondary its heat related guaranteed lots of slip even with a good set up its hard to mange 300 hp with the constant on and off of trail riding on a 2-300 mile day of riding especially when running beside another 300 hp sled all day. I had a stock secondary come apart on me a few years ago. Stm makes a great product thats why you see all the 600- 1000 hp sleds using them in the hypersports camp.

Clutchmaster and I don't buy it either. Its just plain not strong enough to go miles on a turbo trail sled with the heat cycles up and down involved.

There are no complaints of the Pro-4 cracking anywhere and thus the reason for him going that route. We'll see how that one holds, but its thicker where it needs to be in this area too compared to the STM he claims.

I see some reports of the stock Winder secondaries cracking as well, I'd guess from the same heat cycle problems. I'm sure any clutch could come apart but I don't recall many old style button Yamaha secondaries cracking do you Ernie?

 

[Richard Hodgins]

I had an STM on my 1100 turbo and also experienced the same cracking. Needed to replace it. Also had to replace bushings every year on the sheaves.
My Team secondary has been way more reliable on my xf9000 surprisingly! 18000kms trouble free at 270hp.
If I wanted an aftermarket secondary again it definitely wouldn't be an STM....