XL500's smoking, got me stumped (long)

I've restored an 82 XL 500. Part of it was getting it bored one size over and a Wiseco 12.5:1 piston, rings, pin installed. Put new valve springs and seals on and lapped the valves. After about two hours of riding, the piston froze. Autopsy revealed that the inboard end of the cam was galled, some chafing on the cam chain, slight galling on piston/cylinder but didn't affect rings.

I changed a gear around to solve the chain chafe problem, got new valves and had new seats put in for the exhaust valves. Clean up the cylinder, piston, and ensured that the rings were free and aligned properly. Greased/oiled everything while buttoning it up. I checked the oil pump parameters and ensured the o-rings were seating properly (new o-rings). Poured in 2 qts of oil and a shot in the plug hole. Kicked it over a few times then lit it off. Plenty of smoke. Some was the shot in the plug hole, more may have come from the freshly oiled air filter. Rode it around the block a few times, it got hot, wouldn't start till cool. Started, rode it home still smoking. Detached the compression release cable attached to the kickstart to ensure it wasn't holding the valves open and started it again. Still smoking but less.

Is this just part of the valves/rings seating or is something wrong. Tomorrow I pull the rockerarm covers and see if there's oil in there and check out the cam/chain.




From what you describe, it sounds like you reused the piston and rings. Even what looks like a little scoring can burn a lot of oil. If you could feel any scratches in the cylinder it needs at least a hone and probably new rings. That would explain your smoking. What I would be more worried about is why did the piston seize and why is the top end damaged? It sounds like a lack of lubrication. I have seen the exact same symptoms on a newer XR when the oil filter is put in backwards. I don't know a lot about 82 XLs, but if its like the newer XRs I would loosen the oil line going to the top end while its running and make sure oil comes out.

Good luck with it and let us know what you find.

If the oiling system is working properly, are you sure it's not running lean?

If your piston siezed after a bore, I would suspect the piston/cylinder clearance was not correct. Maybe it was calculated for a water cooled engine? Did the shop have the piston when they did the bore? On second re-build, (after the seize), did you mic the cylinder for roundness? If the piston did sieze, there is cylinder damage and will need at least a hone.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now