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440 snowmobile

A

Anonymous-0

Well-known Member
i have a scorpion 440 cuyuna engine in it put new pistons in 2 years ago started this year riding with fresh gas went out riding for an hour when it started bogging down tore it down found holes in both pistons trying to figure out why.
 
Did you clean the carbs before you went out this year? Gas will gum up and plug up the carbs, hence you may have been to lean. Also was there ethonal in the gas?
 
Detonation/knocking/pinging. As previously stated from lean mixtures and low octane fuel.
Too much lube oil will also cause the same symptoms.
 
Buickddeere, "too much oil will cause the same symptoms" What planet are you on. Too much oil would never cause a 2 cycle to burn holes in the pistons. Maybe foul it out or be to rich, but never do that. Im assuming this guy has a pre mix sled, if not how would the oil injector add to much lube.... Yes poor octane fuel could do this, but not too much oil.
 
I had an ultralight aricraft, Rotax Ralley 2B, and it had a Cuyuna engine two cylinder two stroke on it,I think it was a 440 found out later the engine was no good as it was replaced later with a Rotax engine...

Glad I only flew it two times


~Will
 
Buiuckddeere has it..you leaned the mixture screw too much and it got too hot and took the pistons out,BUT....it could also have leaned itself out if the carb got gummed up from sitting..I took the pistons out of a year old machine because I didn;t drain the carbs for storage...now I use fuel stabalizer and I start the machine every month and let it run a while
 
Detonation, but why?

Where are the holes located?

If they are close to or right on the edge of the exhaust port side of the piston, a lean condition stemming from improper carburetor operation or vacumm leakage likely caused the problem.........

If the holes are closer to center of the piston, causes may lean towards too low of octane fuel, overheating(inadequate coolant circulation or air flow if engine is fan cooled), incorrect timing, etc............

Before the engine is operated again after the pistons are replaced the carburetor/s should be completely disassembled and properly cleaned. Proper jetting(or high speed adjustment) for your altitude should be confirmed at that time.

Proper cooling system operation should be confirmed. Proper heat range of spark plugs used. Confirm there is no leakage from engine crank seals, base gaskets, carburetor boots etc., that could causing a lean mixture...........

Lastly, use quality fuel. Premium at least............
 
To much oxygenators present in street fuel these days for fuel stabilizers to be truly effective, better to drain everything before storage!



Scott
 

Oil has a very low octane rating and oil displaces gasoline.
So too much oil lowers the fuel octane causing detonation. Reducing the amount of gasoline by displacing it with extra oil makes the engine run lean.
Things are not what they seen at 1st glance.
Most engine fail not due to "no oil". It's usually one of the three factors and usually in a combination together.
Too much lube oil, too low octane 87 cheap grade gas and too lean of a mixture.
 
I had 3 of those rotten snowmobiles years ago and had the same problem. I was told that the scorpions had throw away engines and need to be replace instead of overhauled. Good luck
 
I had a 1980 Scorpion Whip with the 440 Cuyuna. One of the best little engines I've ever seen, that thing was bulletproof, extrememly reliable, and powerful, it just kept on going. I heard that this is why they were put in ultralight aircraft. Now my engine could have been an anomaly, but I would not hesitate to buy another.
 
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