valve seals bad??

[TD53]

The 400 is smoking at start up, also when i am at high rpms and i let off it always puffs out white/blue smoke. Does this mean my valve seals are bad?

[400exrider707]

Could be that or a combination of that and rings. Time for a rebuild.

[SHADETREE101]

i would replace the rings and seals, just to be sure.

[kd5sfq]

I would tear it down and look at things... It's easy to say it's this or that, but the truth is, you won't know what is wrong until you open it up and inspect everything. Rings or seals may fix it but you might also have a scoring around your piston and sleeve as well. You may or may not need to bore it some to correct your problem.

If your a do it yourself kind of guy. Buy a service manual, read it, understand it and then proceed. Else take it to someone you trust and is honest.

[TD53]

ok thanks guys! Never took apart any kind of engine before but I'm a pretty smart guy, if i had the service manual could i do it myself?
is there any certain tools i'd need other than wrench, sockets etc.?

thanks

tyler

[kd5sfq]

Nothing special for the top end... The Clymer repair manual for the 400ex has a good list of what you need. Lot's of photo's and easy to follow instructions...