Need some advice from the tech gods.

[TheMuffinMan]

Hey guys. I'm trying to shake down a hard starting skandic 440 fan. She's a bitch to start cold but once warmed up it seems to run and start just fine. It likes to die when engaging the rer as well...it works maybe one in 5 times. Cleaned the carb, new plugs, clean air filter = no change. I'm thinking compression is the culprit: I'm at 85 on the mag side, 75 pto side. I'm assuming this is low even for a fan cooled sled, web search turned up mixed results but most say it's too low. Just hoping someone could confirm my suspicion before I tear the jugs off this thing. Thanks!

 

[boots]

Ski doo had primers but if you primed it wrong it was a really bitch and if you didnt prime it was impossible to start


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[underdog]

The compression does seem a little low, but even more of a concern is the 10 psi difference between the sides.

 

[Modman]

Hey guys. I'm trying to shake down a hard starting skandic 440 fan. She's a bitch to start cold but once warmed up it seems to run and start just fine. It likes to die when engaging the rer as well...it works maybe one in 5 times. Cleaned the carb, new plugs, clean air filter = no change. I'm thinking compression is the culprit: I'm at 85 on the mag side, 75 pto side. I'm assuming this is low even for a fan cooled sled, web search turned up mixed results but most say it's too low. Just hoping someone could confirm my suspicion before I tear the jugs off this thing. Thanks!

Is that hot compression or cold compression? Seems low to me, although hard starting when hot is usually a sure sign of too low compression. Is it choke or primer? Choke may need to be adjusted higher for cold starts if cable has stretched over time. The fact that it dies when going into reverse suggests that it might be compression as well though. Yes, 10 PSI difference is too much if those are the actual numbers, but this could be some margin of error in the gauge. Need to pull head and y-pipe at least and measure piston to wall clearance and look at blow-by on rings to determine if you are at the wear limit. Sounds like it though.

 

[TheMuffinMan]

Thanks for the help guys. I checked the compression both hot and cold and oddly enough it didn't seem to make any difference in the numbers. I pulled the cylinders off and sure enough, piston to cylinder clearance was double the limit and the ring end gap was right out to lunch. Luckily the cylinders are in good shape so I think with a quick hone, new pistons and rings she'll be ready to rock. At least until some idiot at work breaks something else on it.