vmax 800 Engine problem?

D

Dennis

Banned
I Just bought a 800 95' today. Wery cheap. The intension was it was for spares, but beside hood, seat cover and suspension it looks quite okay. so maybe it is a rebuild projekt.
But i noticed something about the engine when i tried to turn primary back and forward.
It seems like there is something wrong with the gear from engine to primary.
I can turn primary back and forward cuite a bit before it turns the engine. maybe 20 degrees. in all before engine turns.
There is no strange sounds when engine turns. I tried the same on my 750, and there is no free play in that one.
The engine was running when they stopped using the snowmobile. it has 7200 km. on it.

Is this okay?

I Dont want to take any chances and try to fire it up, before i know all is good.

Thanks.
 

Maybe the spline or the absorbers (dampers?) in the crank gears? Do they shrink with age maybe?
 
I know it's alot of work but I agree I would not light a fire in that until I figured out why that slop is there......

+1 on opening that motor.
 
and your sure the clutch is`nt slipping on the shaft?

i think they all have some play, but exactly how much i don`t know? (talking about the gears, not the clutch..LOL
 
well. I took another look today. i removed spark plugs to see when piston moves, turning the primary. It turns out, when i rock primary back and forward, recoil side cylinders has a freeplay compared to clutch side.. so you can turn engine a bit at the primary clutch but only clutch side responses at once. recoil side is slow on responce. this freeplay is when i move clutch 1cm each side. The other 20 degrees turn "funny noise" is linked to this problem i think. It is not a 20 degrees freeplay to engine. this noise comes when i turn engine a little faster each way

So it is time to open engine.

Thanks for advices.
 
The 750's have two different sized gears on the crankshaft that fit inside each other and the larger one drives the clutch shaft. They are metal to metal mounted to the cranks (if my ageing memory serves me). The 800's have two same sized gears that sit side by side to drive the clutch shaft. They are rubber mounted to the cranks. This was done to help eliminate the harmonic vibrations that came from the 750's when they were run over 9000 rpm (the reason for phasing to 180*). If your recoil side rubber coupler is hooped, the crank will still turn but there will be slop and freeplay. Many guys running their 800's over 9000 rpm went back to the 750 gears with the solid mounting. The rubbers seem to break down at high rpm. It would seem that the harmonics caused by high rpm is still there and destructive in a 90* firing pattern, it's just masked by the rubber mounts of the 800's cranks.
Hope this helps shed a bit of light on your issue.

Ian
 
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