sled only runs on one cylinder after full rebuild. HELP!

03viperguy

03viperguy

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so, my 500f skandic had a noisy bearing on the crank. sure enough, the plastic races disintegrated and it needed a crank. new crank from ski doo, along with pistons, rings, bearing, and full seal kit, all oem. reassemble everything (with the help of a doo tech) and now it only runs on one cylinder. tried readjusting the air gap on the coil pickup, no change. swapped the plugs around, no change. seems to have decent spark.I pulled the carb for the mag side (the side that wont run) cleaned and reinstalled. didnt see anything in there, but now I am certain its clean. no change. BUT, if I put my hand over the carb air intake (airbox off) an block almost all the air that side picks up and starts to run. could the crank seal have fallen out on that side? anyone have ANY ideas? thanks, been scratching my head for day and a half and really just want to get it running, broken in, and start grooming again!
 

What you describe is typical of a crank seal or crankcase leak of some sort. Perhaps the tension spring of the seal came off during installation.

If you rev it up does that cylinder wake up?

Is this a rotary valve engine? If not, maybe reeds?
 
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swapped carbs around, no change. pull out the choke just a tad and it picks up the other cylinder. really sounds like an air leak
 
found the issue, a misaligned intake gasket between the aluminum intake tube and the motor itself. runs great now!
 
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