toydoc
Member
Maybe the weights are a hair short and can overshift to the point of rolling past center. Without the belt, clutch would slap face to face and weight could go by the rollers and endup on the outside of the roller. That would break all 3, and give you the odd break spot in front of the weight.
Just a thought...inside of the weight should have some marks also if that happen.
Just a thought...inside of the weight should have some marks also if that happen.
failure analysis
I have been trough failure analysis classes and can help to guide you to the initial point of failure. Look at all the fracture surfaces on the weights and clutch. If they had any stress cracks in them that grew longer over time the fracture surface will look dull along about 3/4 of the fracture surface and then be nice and shiney/grainy at the point where the catastrophic failure occurred. If the fracture surfaces of the parts are shiney/grainy all along their length then they were snapped off by an impact (brittle failure) most likely caused by something hitting them. Deformations at the edges of the fracture surfaces can tell you something as well. If they are dull they are from an impact or force that caused the defromation in the past. If they are shiney they are from a very recent impact/force. The most common location for a stress crack to start is along the edge of a surface that may have been damaged by a tool hitting it or a pry bar pressing against it all of which I have seen people do when taking clutches off and repairing them. They also start at a sharp interior/exterior surface/corner. Find the fracture(s) that look partially dull and partially shiney and you will most likely have the source or one of the sources of your initial failure.
If it has been several days since the blow up or someone has handled the parts on the fractured surfaces it may be difficult to determine what is what.
Mills
I have been trough failure analysis classes and can help to guide you to the initial point of failure. Look at all the fracture surfaces on the weights and clutch. If they had any stress cracks in them that grew longer over time the fracture surface will look dull along about 3/4 of the fracture surface and then be nice and shiney/grainy at the point where the catastrophic failure occurred. If the fracture surfaces of the parts are shiney/grainy all along their length then they were snapped off by an impact (brittle failure) most likely caused by something hitting them. Deformations at the edges of the fracture surfaces can tell you something as well. If they are dull they are from an impact or force that caused the defromation in the past. If they are shiney they are from a very recent impact/force. The most common location for a stress crack to start is along the edge of a surface that may have been damaged by a tool hitting it or a pry bar pressing against it all of which I have seen people do when taking clutches off and repairing them. They also start at a sharp interior/exterior surface/corner. Find the fracture(s) that look partially dull and partially shiney and you will most likely have the source or one of the sources of your initial failure.
If it has been several days since the blow up or someone has handled the parts on the fractured surfaces it may be difficult to determine what is what.
Mills
I looked for stress cracks in them, I didnt see any however it was hard to determine beacause of the plastic from the belly pan they hit, The area where the weight broke is fresh gritty looking, not like a fatigue crack.
The best I can figure is WOT the belt decided to come apart when that happened it spun the clutch weights, over extending them and thus ripping them off. I am going to rebuild it but I am going to use the 8DN weights instead of the 8CA.
The best I can figure is WOT the belt decided to come apart when that happened it spun the clutch weights, over extending them and thus ripping them off. I am going to rebuild it but I am going to use the 8DN weights instead of the 8CA.
toydoc said:
I think Doc is right on here. If you look at the pic of the cover, you can see where the weight came past the roller, the cover slammedshut, broke the cover and the weight. JMO
sgauthier
Member
had a comet clutch come apart like that years ago on my 95 vmax 600. caused $2000 worth of damage. destroyed the primary, clutch cover, side panel, and secondary. chunks came out the side panel and right throw the left foot well. good thing i didn't have my foot where it was suppose to be. i would have lost a couple of toes for sure, made a inch hole right in the middle. I learned 2 things from that experience. i will never use a comet clutch again and i will never use a crappy dayco belt. i've always stayed with Yamaha parts after that. I am running heel clickers in my SRX thou. I always check for stress cracks on everything, sheaves weights, rollers and the cover. they are known for stress cracks on the fixed sheave ( i've replaced that last year) and on the moving sheave, look at casting were the weights are mounted, around the pins, they can crack there as well. friend of mine found that on his wives SX at the beginning of the year. glad to hear your alright and didn't get hurt, the machine can be fixed.
PS you might want to check your crank after an explosion like that, it sometimes bends it which means you might need a new crank as well.
PS you might want to check your crank after an explosion like that, it sometimes bends it which means you might need a new crank as well.
Last edited:
maxdlx said:
Yep, I agree. I just dont want it to happen again...=)
Danger Dog
Member
Well I must of got lucky. I had a belt snap last weekend on the lake running heelclickers and doing 120mph by the dream meter. It did tear up the clutch guard pretty good. I figured it was because I am geared for 660 and I ran way past that.