SNOWRULES
New member
Had the sled out last weekend and all of a sudden sled was down on power so pulled over pulled the plugs and found aluminum on the PTO plug. Towed the sled home pulled the head and found the piston had melted on the exhaust side and ring snapped and cooked the cylinder and head. Have had at least 250km's on it this seaon with my new power inc pipes and the jetting setup that was in it when it burned down. Was doing full out speed runs the day before in the same temperatures holding it wide open for over 2000' runs. Just wanted to get some input on what you guys think might have caused the burndown. I was thinking bad crank seal or air leak somewhere. seeing as it was pretty sudden i guess it could have been dirt in the carb, but i had cleaned them at the start of the season when i changed my jetting. also filled the carbs with seafoam and ran seafoam in the tank of gas that same weekend. also had done plug checks the day before in the same temps (i'm pretty decent at jetting by plug color) and to me they were plenty rich.
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the_dream_theater_nut
New member
Am I wrong in thinking that since you only have one bad one, it cannot be oil delivery, but must have to do specifically with that one cylinder,which almost has to be an intake air leak or lean carb? I'm trying to learn by asking questions, so I hope you'll bear with me. Perhaps I can pass it along some day. Thanks. Steve.
Skidooslayer687
Member
might be worth the $ to get a crank seal and pop it in while your this far.... peace of mind when its back together... just my 0.2 cents
SNOWRULES
New member
ya i'm getting all 3 cylinders replated, new base gasket, crank seals, cylinder head o rings, all new pistons and rings while it's apart. has 13 000 km's on it it's due for a freshen up.
SNOWRULES
New member
anyone know if that piston wash looks ok ? the domes look pretty clean but then again i ran seafoam through it and it's supposed to be a decarboniser. and there was still some in that tank when it went.
Do you have a leak in that carb boot or you could have something blocking that jet?
I think the other 2 pistons look pretty good, the wash looks good, I can see the rear transfer swirl and it has brown in the center, pretty much perfect. Remember these things like fuel upstairs, fuel is MPH!! The one thing I do see is alot of oily residue on the bellypan/front frame, are the exhaust pipe donuts in good shape? if these are leaking or your pipe joints sloppy and leaking could be the problem, it looks like to me in the pics the pto was the worst offender.
When you do those boost holes in the piston, be carefull they are offset to the top, not just drilled out.
When you do those boost holes in the piston, be carefull they are offset to the top, not just drilled out.
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SRX7
New member
Any time I take my carbs off to clean them or any thing I take off to do with the intake I always spray some carb cleaner around those areas to make sure I have no leaks. But in your case could have been a little dirt or water you never know.
You wanna play you gotta pay just the nature of the beast.
You'll get her back together and away ya go. Good luck.
You wanna play you gotta pay just the nature of the beast.
You'll get her back together and away ya go. Good luck.
SNOWRULES
New member
hey don sorry was away for a few days. what do you mean by the holes are offset to the top? do you mean the hole isn't just enlarged from the existing center but that it's enlarged but the center is slightly moved towards the piston crown? beleive it or not that oil came from the powervalves not from the bottom of the pipe joints. i usually grease where the cable slides into the end of the powervalve and that whole kinda spring area in behind where the cable connects. i think maybe i was too liberal with the grease and when it got hot and melted it all it turned into a black mess that sprayed out the weep hole underneath them. i did however have a bad seal where the pto pipe met the exhaust silencer. using powerinc pipes and the fitment is a littl off hard to get a perfect seal on that one pipe. maybe next time i need to be more careful about that sealing up right.
yes, thats exactly what I mean on the holes.
SNOWRULES
New member
ok sounds good, i'll just measure off an old one and make sure the new ones match up in exactly the same spot. thanks again. hope she runs good as new with the new plating and pistons.