I'm new to the forum and trying to get an 86 trx200 back in good running condition. After cleaning the carb up, I started it up, but could not get it to run smoothly and it was burning oil bad enough to fill my garage in a couple of minutes.
I began pulling the cylinder and head and checked the marks on the cam sprocket before I removed it and found them to be off by a couple of teeth (probably the cause of it not to run smoothly). After getting it all apart I found a lot of carbon build up on head, valves, piston and the valve seals were pretty hard. After cleaning all the carbon off, polishing the valves and piston, I put new valve seals, O-rings and gaskets on and put it all back together. I didn't replace the rings because I did not see any excessive wear or damage.
I started it up and noticed it was running much smoother, but after about a minute it began smoking heavily again.
I've got it all apart again, and the only thing I can think to do now is to replace the rings and maybe the piston but I can't really see anything wrong with the piston. I checked the cylinder again really close and can't see any damage and the diameter measures within a few thousandths from top to bottom and front to side.
Any other suggestions would be welcome and appreciated.

 

The exhaust will be full of oil, take it for a long run then let it cool down, and it may stop smoking. If it does need to be stripped again, to measure rings for wear is the easiest job, yet no mention of you having done so. The piston skirt diameter should also be measured, preferably by micrometer rather than digital calipers. Acceptable tolerances for both ring gaps and piston diameter will be in the service manual. All this is irrelevant if that "few thousandths" is more than about 0.003" as that is the maximum bore wear I would leave. Over 0.004" and Honda say you need a rebore, so new oversize piston and rings anyway.