You really should do both sides and not just rebuild 1 of 2 cylinders.
Some people will argue this, but I'm telling you straight up, this is the right way to go about it.
When you re-build just 1 side and not the other, you are just asking for that other side to let go and cause another re-build and possibly other, more expensive damage.
Get your copy of a shop manual, or at least coppies of that section, and follow it exactly as shown in the book.
Flush your bottom end and check your crank run out while it's apart.
You don't want anything in there to cause you to re-build this again next week.
Don't forget to lube all bearings after flushing.
Be sure to measure out your ring end gap and bore diameter.
Get your bore diameter in 2 directions in 3 locations, 1 at top of cylinder, 1 at middle, and one at bottom.
Make sure everything is in spec.
Torque everything to spec and in the right order.
Very important to go in right order.
Take your time with it.
Replace both pistons, wrist pins and bearings, and sets of rings.
Do not re-use any gaskets or O-Rings.
Go with OEM and not Weisco, Seizco sucks.
Don't forget assembly lube.
You will have to break in your new top end too.
Warm up completely before each ride.
50:1 mix oil in the gas, no full throttle your first ride out.
Bring extra plugs, all that lube is bound to foul at least a set or 2 at first.
Plugs are cheaper than motors though, so go with it.
Vary the throttle lots for the first 2 rides out.
Be easy on it the first 2 rides out,
but some full throttle is OK on second day.
3rd day on, warm up for each ride and then ride like you normally would.
Do all these things and your motor will probably thank you by lasting a good long time.
A forum community dedicated to snowmobile owners and enthusiasts. Come join the discussion about performance, racing, troubleshooting, trails, maintenance, riding tips, modifications, classifieds, gear, and more!