(this scenario presumes that the engine will NOT be
torn down and the crankshaft replaced)
A check should be made to make sure there is not oil or gas sitting in the bottom of the crankcase area – remove the spark plugs, push the bike (down a hill if possible) and put it in gear – if there are any signs of liquid coming out of the spark plug holes as the engine is turning over, STOP and take measures to remove ALL liquid in the crankcase area before going any further.
A crankcase leakdown/pressure test should be performed to insure that the crankshaft seals are good and to confirm that you do not have air leaks somewhere that will cause the bike to not run properly or could cause damage due to a “lean” condition
- IF it passes these tests – you MAY not need to replace the crankshaft – however, the crankshaft bearings still may be bad and if the engine is run, you may suffer damage as a result
A compression check for each cylinder should be done to see if the rings and head gaskets are OK (should have between 130-150 psi)
The cylinder heads should be removed and carbon should be removed from the heads and piston tops
It’s a good idea to remove the exhaust head pipes and mufflers and remove any carbon build-up.
Try to remove the baffles from the mufflers and remove any carbon build-up on the baffles also.
Check to see if the carburetor intake manifold gaskets are in place, not rotted and the mounting nuts are snug (on the H2 verify condition of the rubber adapters).
Check the ignition timing for your bike, including air gap or point gap – adjust to specs if needed
Always a good idea to install a NEW set of properly gapped spark plugs
If possible, put bike on center stand or elevate the rear wheel so that you can shift through all gears and listen for any unusual noises to make sure the transmission is OK and you don’t have any bad gears or clutch parts.
Remove and replace the transmission fluid with a good transmission gear oil, i.e. Belray Gearsaver 80-85 wt. Fill to proper level.
Tighten all nuts/bolts – especially check engine mounts.
It is a good idea to check/adjust the shifter
parts/linkage so you do not have any "slop" in it. You want to make sure the
shift lever does not hit a footpeg or the muffler before it "solidly" rotates
the shift drum to engage the next gear.
Check the kickstarter and make sure it is firmly secured on the kicker shaft. It is common for the kick boss (the part that is attached to the shaft with a bolt) to get "stripped" and turn on the shaft w/o turning the engine. Make sure the bolt is tight and the splines are not stripped.