Why do Snowmobiles not have a wet clutch before the primary?

[Donnyvan]

I recently purchased a Yamaha Grizzly 550 and had to replace the one way bearing on it. I thought it was a really cool design that yamaha decided to use a centripetal wet clutch before the primary. This allows the clutch plates to rub as opposed to the belt, allowing for a belt to never slip and more or less never need to be replaced. The polaris quads have a similar set up to sleds with just the dry clutch which causes belts to blow out more than the yamaha ever would. This also creates a similar "snap" when taking off from a stop, similar to sleds. The grizzly can crawl just like an automatic trans in a car without any fear of burning a belt. The only reason I can think of for sleds not having that is added resistance in the drive train, but for those who use their sleds for work as opposed to going fast, I feel like the added reliability would be worth it. And then you can crawl along in the garage/parking lots without spinning a track (which I find super annoying with low snow and studs). Could also help you crawl out of a hole instead of digging it deeper. Is this just a stupid thought because sleds are meant to go fast and not crawl? are there machines made with this setup that I am unaware of?

Love to see what others think.

 

[MrSled]

I recently purchased a Yamaha Grizzly 550 and had to replace the one way bearing on it. I thought it was a really cool design that yamaha decided to use a centripetal wet clutch before the primary. This allows the clutch plates to rub as opposed to the belt, allowing for a belt to never slip and more or less never need to be replaced. The polaris quads have a similar set up to sleds with just the dry clutch which causes belts to blow out more than the yamaha ever would. This also creates a similar "snap" when taking off from a stop, similar to sleds. The grizzly can crawl just like an automatic trans in a car without any fear of burning a belt. The only reason I can think of for sleds not having that is added resistance in the drive train, but for those who use their sleds for work as opposed to going fast, I feel like the added reliability would be worth it. And then you can crawl along in the garage/parking lots without spinning a track (which I find super annoying with low snow and studs). Could also help you crawl out of a hole instead of digging it deeper. Is this just a stupid thought because sleds are meant to go fast and not crawl? are there machines made with this setup that I am unaware of?

Love to see what others think.

My first guess would be added weight and all the grease you have to pack into the primary would not be great in the winter months.

 

[Donnyvan]

My first guess would be added weight and all the grease you have to pack into the primary would not be great in the winter months.

all but one bearing is inside the oil on the quads so I don't think it would be any more issues than the bearings already present and the belt clutches would function the same way as they do already, there's just a wet clutch between the primary and engine output shaft. Weight makes sense though, it would probably add 20lbs and take up alot more space in an already cramped area. But are we yamaha folk really one to comment on weight?

 

[RON HYDRAULIC YAM]

Yamaha did similar in some sleds in the early 70's .. I discovered the patent was applied for
in 1968 and first production was the 72 EW643. I'm guessing they figured out quick that slipping
belts were trouble.
Of the near 40 fluid drives i've brought home , only one had a bad belt because the tunnel had rusted
out under the engine and probably got closer to the driven every time these goosed it.
Eventually they all figured out how to build better CVT units and you no longer had to carry two extra belts ..
..
They rode a bit like an automatic stuck in 2nd and no reverse... the wide tracks used the HI N Low chain case.
.
The Almn engine pulley weighs near zero and the convertor was all Almn as well so they weighed about
the difference of a quart of dextron ... BUT cost more to build then a stamped out clutch..
The 1/2" pitch timing belt also just weighs near zero.
...
I also have a VIP Cat with their version . They originally had no disconnect and were difficult to start cold but
the Yams had a Neutral in narrow sleds and the H neutral L in the wide sled .
... 1972 to 1977
Ron