I have a '97 315R which runs pretty good, but needs a little help. When cold it will start on the third kick most every time. When hot, and it sits for 5-10 minutes (like when you're waiting for your turn at a section) it won't start without using the choke. The spark plug indicates that it's running pretty lean (whitish, light brown color). Another thing, maybe related, when I'm riding it with no load, level ground at steady speed, the engine, as best as I can describe it, oscillates. It sounds like "whump, whump, whump". Any problems there? I figured I'd ask you guys before I try to fix this on my own.

Start by cleaning the carb, it sounds like a bit of dirt is restricting the pilot jet

Yeh...I agree with Ishy sounds like the pilot jet is dirty.Classic symptom of hunting from the engine.Give the carb a really good clean and try again.

Had the same prob some years ago on a 311 mont and it turned out to be the jet,learn't my lesson then.

I cleaned the carb and blew out all the jets. It all looked pretty good. No obvious restrictions. Put it back together and it started right up. Ran it for 15 minutes, adjusted the carb, then shut it off for 10 minutes. Wouldn't start without a choke. It's still pulsing (better word than oscillating) too. Any other ideas?

Ok...check that the connections between the engine and the carb/air filter box are airtight .