Primary clutch exploded

[snowbeast]

Many are switching back to the previous style primary (Viper, Nytro, Apex...etc.) with great results and zero issues

The 2018 apex is the last year of its life,and if that ape clutch is still any good,and a direct bolt on,you can buy it on babbitts for $429 plus shipping,that complete and ready to install,less ramps or spring.

 

[sideshowBob]

I still think gearing these sleds so the clutch doesn't fully shift out will help or totally alleviate these failures.
When the primary fully shifts out and comes to a mechanical stop, the engine/clutch RPM will start to increase which continues to increase the fly weights energy that now has no where to transfer its weight except to the clutch rollers/sheave. The energy is normally transferred and absorbed by compressing the primary spring, squeezing the belt, and opening the secondary, all of which absorb the energy cushioning the flyweight mounting pins and roller mount/sheave.
Everything has its breaking point and a 75-80 gram weight spinning at 9000+RPM on a 3-4 inch radius has huge mass/energy.

JM.02c

 

[BlueByYou2000]

I still think gearing these sleds so the clutch doesn't fully shift out will help or totally alleviate these failures.
When the primary fully shifts out and comes to a mechanical stop, the engine/clutch RPM will start to increase which continues to increase the fly weights energy that now has no where to transfer its weight except to the clutch rollers/sheave. The energy is normally transferred and absorbed by compressing the primary spring, squeezing the belt, and opening the secondary, all of which absorb the energy cushioning the flyweight mounting pins and roller mount/sheave.
Everything has its breaking point and a 75-80 gram weight spinning at 9000+RPM on a 3-4 inch radius has huge mass/energy.

JM.02c

This is spot on. Gear higher or get out of the throttle when you see 120.

 

[Sidewinder Bob]

Just checked for cracks around set screws. okay at this time with evo stag 4 and 3000 miles. I also use the 911 cover. wonder if this help to stop the cracking?

 

[kviper]

Just checked for cracks around set screws. okay at this time with evo stag 4 and 3000 miles. I also use the 911 cover. wonder if this help to stop the cracking?

I ordered a 911 cover a couple days ago! Certainly can’t hurt!! I think blowing up and roller wear is from movable shiev flex. 911 cover will make the clutch more rigid. If the cover can’t flex the towers can’t flex and the movable shiev will be less likely to flex. If the movable shiev flexes the weight is working on the roller.

 

[kviper]

This is possible, I have a set off HH kicking around here from an old turbo RX-1 though and they too are shorter. It's quite easy to see, or maybe I should say were shorter than all the others. Not to say they haven't changed them over the years. I'll dig around and see if I can't find them somewhere.

The part that gets me is every picture THAT I HAVE seen of broken or blown Winder clutches, has had HH's in them when they have let go, haven't seen any other pictures of blown clutches mentioned anywhere else with stock or any other brand of weights. It's always the HH weight, just what I have noticed in all these pictures, so is it too much dead weight on the heel and pivot point just over stresing the pivot? Could it be the weighs are breaking at the threads and then blowing out? I've seen pics that show these weights broken at the threads, but which came first, the broken arm or the broken clutch?

If theres other clutches out there with something different in them for arms, then I'd like to see the postings or pictures of stock or other weights along with that blown clutch. There must be some links to all these blown clutches that are out there. From the sounds of it there must be a rash of them coming apart. Weird part is this being the go to Yamaha site, I've only seen talk and pictures of a select few. And everyone of them had the same weight design in it. I'd be pizzed if it was my clutch exploding because it wasn't strong enough and posting plenty of pics to warn others of the impending doom so it wouldn't happen to them.

My clutch eats rollers for breakfast and rattles like a SOB at idle and 35-50 MPH or so, same as my 1200 did with the rattling bucket of bolts TRA. Hence the reason to try the Team Primary and the PB80 at some point.

My friends clutch had STM’s in it when it let go.

 

[journeyman]

I'd guess thats the problem here. Worn rollers and those shorter than most, Heavy Hitters rolled right past the worn out rollers and bang, ripped them right out of the clutch as it was fully shifted out. Every one I've seen broke has had these HH weights in them.

The clutch did not completely explode though, which is good. I don't see this as a Yamaha clutch problem, other than the worn out bushings. The HH arms are just shorter than they probably should be. Fine with good rollers, but worn out bushings and they roll right off the roller. Set them side by side with most any other brand weight and you'll see how much shorter they are.

Yes they do appear shorter but maybe it's the heavy heel area that creates the illusion?? I ran them on my 2 stroke Yamaha's some years ago with good success. Obviously those machines did not have the HP and torque these things are capable of putting out. I do like the Dalton weights being you can add weight to the arms without taking the clutch totally off.

Interesting info from Thunder Products though. I have been wondering if Yamaha has sourced the manufacture of this clutch to someone else?

 

[Warren Silliker]

I had this happen as well, STM Weights 270 flash, Arm flew thru belt gaurd, airbox, hood and into orbit i believe. Thinking bad roller may have been the issue tho

 

[Wingwong]

Has anyone experienced any problems with dalton weights?

 

[Crossfire12]

It’s the clutch, clutch, clutch sucks with big HP, not the weights, big HP ,bigger weights, or get bigger stronger clutch, or stay stock HP. You can’t fix that clutch! STM! TAPP etc.

 

[Fleecer]

The 2018 apex is the last year of its life,and if that ape clutch is still any good,and a direct bolt on,you can buy it on babbitts for $429 plus shipping,that complete and ready to install,less ramps or spring.

The older clutches will work, but they dont have the overdrive like the winder clutch.

 

[Fast]

I still think gearing these sleds so the clutch doesn't fully shift out will help or totally alleviate these failures.
When the primary fully shifts out and comes to a mechanical stop, the engine/clutch RPM will start to increase which continues to increase the fly weights energy that now has no where to transfer its weight except to the clutch rollers/sheave. The energy is normally transferred and absorbed by compressing the primary spring, squeezing the belt, and opening the secondary, all of which absorb the energy cushioning the flyweight mounting pins and roller mount/sheave.
Everything has its breaking point and a 75-80 gram weight spinning at 9000+RPM on a 3-4 inch radius has huge mass/energy.

JM.02c

What about machining the clutches .020" to allow for some more overdrive instead of gearing it?.010" off each primary sheave .020" off split collar and
.020" off the helix?

 

[Fast]

The older clutches will work, but they dont have the overdrive like the winder clutch.

The overdrive is easy to add simply machine the clutches

 

[Fleecer]

The overdrive is easy to add simply machine the clutches

Yup, that can be done however opinions vary on whether or not that is a good mod. Some swear by it while others have experienced belt flipping over at full shift. Might be dependent on who does the machining perhaps.

 

[1049triple]

In my opinion if you want top speed frequently dont machine for overdrive. Gear for it. Anyway the clutches are dropping efficiency over 1:1. And think about turbo drag cars. They are geared way up.