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

[KnappAttack]

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....

Thats great to hear on the TEAM secondary. It sounds like this might be the only option moving forward as Yamaha may use the Cat clutches? I have a 2020 Thundercat in here this week but have no experience with that secondary. I put a new TAPP on for the primary.

 

[stone88]

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?

I’ve never had issues with the old button clutches other than breaking to many belts trying to get it dialed in lol lots of guys using them on there sidewinder I have an almost brand new one if my race sled it’s a viper secondary but I like the back shift of the roller clutch.

 

[max rolph]

Thats great to hear on the TEAM secondary. It sounds like this might be the only option moving forward as Yamaha may use the Cat clutches? I have a 2020 Thundercat in here this week but have no experience with that secondary. I put a new TAPP on for the primary.

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hey knapp how did you align the sec with the Tapp, just in case i ever need to take the stm off. obviously using a 827 0r 829 belt

 

[KnappAttack]

hey knapp how did you align the sec with the Tapp, just in case i ever need to take the stm off. obviously using a 827 0r 829 belt

Same way I do all/any clutches. Push in on the primary and the secondary to full shift and line up with a straight edge outside the secondary and measure to the belt making sure its perfectly in alignment. I have a bolt I welded a nut on to be able to compress the primary to full shift using a threaded rod and parts of a clutch compressor.

 

[KnappAttack]

I’ve never had issues with the old button clutches other than breaking to many belts trying to get it dialed in lol lots of guys using them on there sidewinder I have an almost brand new one if my race sled it’s a viper secondary but I like the back shift of the roller clutch.

Agree, the Winder roller backshifts much better after trying them both, figured just in case, I'd keep the Viper secondary around as a spare. It works well enough for acceleration.

 

[Turboflash]

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....

My riding group has a combined over 18,000 miles at 280HP or more on stock Team secondaries and there has been zero issues. They just don't show any wear at all. Original rollers are still same diameter, bushings are tight.

 

[Upstater57]

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 am looking forward to the new TAPP secondary when it is released. I am sure it will be as well built as their primary clutch.