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Hey gang!
A good buddy of mine just melted a piston (see picture).
The sled is a 1999 Ski-Doo Formula 3.
The top end was re-built about 5 years ago for a leaking base gasket.
It has run good since but hasn't seen a lot of miles (maybe 1000 - 2000miles since last rebuild)
He was running 87, 89 or 91 Octane fuel in the tank (waiting to get confirmation as his buddy filled it last, not him)
Typically 87 and 89 octane around here are 10% methanol mix and most 91 is not.
He was doing some drags on the lake and it was cold that day (about -35 Deg C or -31 Deg F)
As far as I know carbs are jetted stock.
Compression is stock (not shaved anything or aftermarket gaskets etc).
No after market pipes that I know of.
I haven't seen everything in real life only this picture.
At first i thought it looked like a hole blown in the side perhaps due to backfiring but the top edge of the piston is melted as well.
The damage is on the exhaust port side though.
He does believe he did the damage AFTER the drag when he let off the throttle, not while running full out as he heard a noise after letting off.
So, do you guys think this was caused by simply running too lean because of the cold outside temps? Or any other theories....obviously running drags at cold temps doesn't help but is there a possibility of more issues?
If so is there any way to prevent this (besides simply not running it that hard when it's that cold).
He'd rather not re-jet as it's already running a little rich at higher temps.
(but perhaps that's his only alternative).
Would a higher octane fuel have helped prevent this (like in the case if he was running 87)?
Or is that not likely?
Is he just being too hard on his machine?
Thanks for any info you can give us!
A good buddy of mine just melted a piston (see picture).
The sled is a 1999 Ski-Doo Formula 3.
The top end was re-built about 5 years ago for a leaking base gasket.
It has run good since but hasn't seen a lot of miles (maybe 1000 - 2000miles since last rebuild)
He was running 87, 89 or 91 Octane fuel in the tank (waiting to get confirmation as his buddy filled it last, not him)
Typically 87 and 89 octane around here are 10% methanol mix and most 91 is not.
He was doing some drags on the lake and it was cold that day (about -35 Deg C or -31 Deg F)
As far as I know carbs are jetted stock.
Compression is stock (not shaved anything or aftermarket gaskets etc).
No after market pipes that I know of.
I haven't seen everything in real life only this picture.
At first i thought it looked like a hole blown in the side perhaps due to backfiring but the top edge of the piston is melted as well.
The damage is on the exhaust port side though.
He does believe he did the damage AFTER the drag when he let off the throttle, not while running full out as he heard a noise after letting off.
So, do you guys think this was caused by simply running too lean because of the cold outside temps? Or any other theories....obviously running drags at cold temps doesn't help but is there a possibility of more issues?
If so is there any way to prevent this (besides simply not running it that hard when it's that cold).
He'd rather not re-jet as it's already running a little rich at higher temps.
(but perhaps that's his only alternative).
Would a higher octane fuel have helped prevent this (like in the case if he was running 87)?
Or is that not likely?
Is he just being too hard on his machine?
Thanks for any info you can give us!
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