Motorcycle Repair: 1984 honda blowing smoke., honda xl600r, cylinder hone

Question
I have a 1984 Honda XL600R. When I start the bike, it blows blue smoke for about 3-5 minutes then clears up. Just had the carb. cleaned as it was sitting for a few years in storage. Wondering if it is rings or something more serious. The bike is in excellent condition and if it is worth fixing. Appreciate your feed back and thanks for your time

Clint, Canada

Answer
Clint, a compression or leakdown check would verify compression readings, which indicates any wear or leakage at the piston rings.

Blue smoke is oil smoke.... Sources are: Piston/ring wear, rings sticking in the piston grooves from sitting for years and most probably worn/cooked valve stem seals. Worn or sticking rings will also result in some blow-by coming out of the breather system.

Depending on the mileage and care it has had in the past, it would be worth pulling the motor, doing a freshening up of the top end.. new rings and/or pistons, gaskets, valve stem seals and/or valve job and putting it all back together again. It may not need a bore job, just a cylinder hone and a thorough cleaning of the piston ring lands. Definitely replace the valve stem seals and decarbon the head's exhaust ports and combustion chambers.

If the engine has over 20k miles, it might be wise to replace the camchain and tensioner parts, too.

Bill Silver