i just purchased an 02 400ex. the guy i bought it off of said it needs rings but im not sure. it sat for a good while and when i got it started it smoked really bad. i changed the oil in it and cleaned the carb. i also took the exhaust off and cleaned it out then checked the plug it was good. after all that it still smoked really bad. then i started it another time and the exhaust turned cherry red along with the smoking. does anybody have any suggestions?

 

If the exhaust turned red its getting to much gas, like the choke is stuck. I would for sure put some new rings in it if its a factory 02. Also check your valve seals. Thay could have dry rotted from sitting.

hope this helps

 

Hows the compression? If its still good, the rings proabably are too.
The red pipe comes from either too much time idleing...or a lean idle mixture. Did you check the pilot jet when the carb was apart...its probably partially blocked, or the mixture screw is screwed in too far.( It should be about 2 turns out, or more.)