Primary Clutch Balancing

[sweeperguy]

I'm wondering how many people have their clutch balanced?
Seems to me would be a good idea. I've not done it on the past but if I end up keeping this sled for many years could save me money in the long run. Indy Specialties charges $150 to balance a new clutch. With manufacturing tolerances, and the quantities that they run, can see more than a few being out of balance.
ANY THOUGHTS ON THIS

 

[whitedust]

I'm wondering how many people have their clutch balanced?
Seems to me would be a good idea. I've not done it on the past but if I end up keeping this sled for many years could save me money in the long run. Indy Specialties charges $150 to balance a new clutch. With manufacturing tolerances, and the quantities that they run, can see more than a few being out of balance.
ANY THOUGHTS ON THIS

I think you are better off blue printing if you want to spend the money. What good is a balanced clutch if everything else is off?

 

[ezra]

dan dose a good job and spins all parts separate .

 

[sweeperguy]

I think you are better off blue printing if you want to spend the money. What good is a balanced clutch if everything else is off?

Blue printing? Are you talking the whole internals of the engine? Seems to me that'd be EXTREMELY expensive.
My thinking is that with it (the clutch) being on the outside of the motor hanging off the end of the crank. It's in the spot that any imbalance would be worse there than anywhere else.

 

[ezra]

and if you are changing springs back and fourth you forget to mark or rub it off with dan balancing parts separate it is irrelevant.
for the money it cant hurt . I have had a few done by him over the yrs .he will resurface the faces and bead blast also

 

[whitedust]

Blue printing? Are you talking the whole internals of the engine? Seems to me that'd be EXTREMELY expensive.
My thinking is that with it (the clutch) being on the outside of the motor hanging off the end of the crank. It's in the spot that any imbalance would be worse there than anywhere else.

Just the engine to the,clutch, motor mounts and drive shaft and their relationship to each other if you want to spend some momey. I would not balance clutch or blueprint meaningless to me for trail riding just clutch alignment serves my purpose. If you are constantly in powder at high RPMs a clutch balance would be benefical but again not not necessary for me for big trail miles. Yamaha belts last many 1000s of miles and cheap usually I change just because at about 5000 miles. When I hear $150+for belts and maybe 1000-1200 mile replacement it blows my mind! Imo spend that $150 on gas food or lodging unless you have a clutch problem.

 

[tourguide]

keeps your crank bearings from getting beat down, my belts die of old age now, they get replaced when the rubber dries out and cracks.

 

[skeeter2010]

This is the kind of work I do, onsite balancing and vibration testing not specifically on snowmobiles but industrial machines. As a preventive item I don't think it would hurt to spend the $150 on a balance job for the clutch. I had a friend break off his crank right outside the PTOside bearing the motor ran just fine after it broke just no spot for the clutch. My guess it that was related to a clutch balance issue.
My concern is that most people will not have a way to verify they have truly reduced the 1x vibration of the engine. We have a soft stand at work for balancing and I have been working on getting an arbor built to balance my clutch and to see what effects it will have on the engines overall vibrations.
I will need to pre-check it at a few different RPM and make notes balance the clutch and retest.
Someone mentioned spinning all the parts separately not sure if that is truly necessary however I would most likely pull the weights before balancing.
Just my thoughts I will let you know if I ever get around to building a arbor.

 

[mikedrh]

Arctic Cat and Ski-Doo (at least in the last 15 years, or so, for Ski-Doo) balance the parts individually. They do that so they can sell individual replacement parts as far as covers, spiders and clutch faces.

Polaris and Yamaha balance the complete clutch assembly so they won't sell anything but a complete unit. If you have ever had a clutch disassembled you will never get the spider to tighten to the recommended torque and end up in the same spot (the spider will not be clocked in the same spot in relation to the fixed sheave). You can use shims to get it right but that usually changes the distance between the sheaves.

 

[skeeter2010]

Arctic Cat and Ski-Doo (at least in the last 15 years, or so, for Ski-Doo) balance the parts individually. They do that so they can sell individual replacement parts as far as covers, spiders and clutch faces.

Polaris and Yamaha balance the complete clutch assembly so they won't sell anything but a complete unit. If you have ever had a clutch disassembled you will never get the spider to tighten to the recommended torque and end up in the same spot (the spider will not be clocked in the same spot in relation to the fixed sheave). You can use shims to get it right but that usually changes the distance between the sheaves.

That makes sense to me about the clocking of the spider.

I have not balanced a clutch, however I would almost bet that the components, separately are within spec however once you put them all together and stack up any run out and imbalances once together they may not be acceptable. For example if we use clock positions, if the motor side sheave is 2 gram inches out of balance at 12 o'clock postion (within spec) and the outside sheave is 1 gram inch out of balance at 12 o'clock we are now at 3 gram inches out of balance and then spider is 2 gram inches out of balance at 5 o'clock which reduces the imbalance at 12 oclock and moved it clockwise some it will still be within spec.
However if the spider is out of balance 2 gram inches at 12 o'clock now it has stacked up and you have 6 gram inches out of imbalance at 12 o'clock. This is why with an overhung mass spinning at 8000 Rpm it is important to have the unit balanced. I had seen a chart that gave the forces caused by a known weight at a specific diameter in 1000 RPM increments the lbs forces were huge (in your best Donald Trump Voice)

I spoke with this company last year nice guy http://www.cascadecp.net/Cascade-Balancing.html

 

[mikedrh]

A from the factory clutch is balanced well within spec.

Excessive clearance (worn out) cover bushing and/or movable bushing is extremely hard on crankshafts and the clutch itself.

The extra clearance allows the cover and/or movable sheave to move off center. That mass being off center is way more destructive than a few grams of weight.

Bushings usually wear evenly over the full 360 degrees. If you spin and balance a clutch with a worn out cover bushing, and spin it again, you won't get the same results twice because the cover will off center differently every time you spin it.

It's never a bad idea to balance a clutch but it's only part of the story.

What about the secondary? Nobody cares about the secondary? lol