Sticking a weight on an object spinning 8000+ rpm is not a good idea. Removing weight is the better option

 

Yep, its not like balancing a crankshaft where you can do this.

 

For the sake of argument, if the object of weight was secured properly, what would be the difference?

 

Have you ever seen what happens when a piece comes flying off of a clutch? Losing a toe is an option, that's the difference.

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The stock covers have extra meat added to where they drill. So your not really taking away the strength of the cover. Its made to have weight taken out.

 

Ok. If something could be added without the fear of coming off, are there any drawbacks to doing it this way?
The added meat to the cover is about 3/8” at most. Now take 75% ofnthat away multiplied by about 10 holes drilled in the cover. I have drilled out plenty of them and went through the cover a few times.
And clutches that serve over 600cc sleds, seems like the fixed sheave center shaft is out of round also. Almost all of them have a wobble so I’ve noticed. Lower hp rigs seem to stay true to form.

 

Use some stick on wheel weights, I'm sure it will work great.

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I seriously can't comprehend why anyone would do this to a piece of cast aluminum. With a crankshaft, your dealing with more surface are to fill a drilled hole. If you have a wobble, its not a balance issue, either the crank has excessive runout, or you have a defective clutch that needs replacement.

 

3-8 grams is more than the factory tolerance. 8 grams is almost three times the factory balance tolerance. I have balanced many clutches. Adding weight would not be a good idea on a clutch. If you are static balancing at home and guessing how much weight to remove you probably make the balance worse than original.
Adding weight can be done, but I wouldn't do it with a stock cover. TPI 911 covers for Polaris clutches have tapped holes for adding weight to correct the balance. The fancy Bikeman covers don't have any balancing provisions.:dunno:

Tires spin at about 500 RPM at 60MPH on average depending on tire size to a tolerance of .25 ounce or about 7grams.


A snowmobile clutch at 8000 RPM and 7 grams unbalance equals 70 lbs of centrifugal force swinging around on the end your crankshaft. I suggest leaving the balancing to the pros or leaving the factory job alone. A catastrophic failure at 8000 RPM would not be pretty.


There is much more to balancing than just removing the static imbalance. You could create a worse couple unbalance. Modern professional balancing machines remove static and couple unbalance at the same time, its called dynamic balancing. These can achieve results of around 100mg residual unbalance. 30x better than the OEM tolerance of 3grams.:bc2:

 

Our engine machinest had to make a special fixture tool for the polaris clutch taper to dynamically balance these clutches on his computerized crankshaft balancer machine. The clutches are spun at 500 rpm to find what degree angle they need weight taken off. If you spend enough time you can make a clutch perfect.

 

Your over thinking it. The covers are made to take weight out for balancing. If your drilling through the covers. Your simply drilling too far. The ribs on the under side of the cover are there for strength too. Your not drilling into them.

 

I appreciate each post and an explanation of the whole process regarding factory tolerance. Good info to know. Maybe tomorrow I’ll mess around with the dial indicator to measure any wobble just for fun....but then again, we just got about 10” of new snow. Shouldn’t be a hard decision on what to do!

 

I made my own mandrel that weighs roughly the same as the crankshaft. The clutch sit on the tapered end just like it does when in the sled. It gets balanced with the sheaves closed, no springs or weights. Yes, I can get them perfect, less than 100mg if I want.

 

X2 with our guy.

 

Clutch Balancing - Patrick Custom Carbon – Online Store


Going to send mine out this year for balancing.

 

Drive the clutch over to Jeff for top-quality work and save the shipping, he's done all of ours for close to 20 years.

Wheeler Racing | Honesty, Dependability, Quality Since 1962

 

Could remember the last time getting my clutch balanced back in the 00...cost just a 1/3 of that. Seen where most stock poo clutches on the sleds sold were well within spec., especially if running a stock trail sled. Funny thing was their new clutches sold as replacement parts....many were so far off, those are the ones i'd definitely have looked at.

 

Cascade clutch and performance in Idaho or Indy Dan is where I would go.

 

Might as well do the secondary too, you can improve on them just as much or more. Its free hp.