Valves or Rings ??

[yungair23]

I am blowing blue smoke out and its a good amount too also i have noticed my atv getting slower than it use to be bofore this problem i know i have ruined one of the two valves or rings but which is it?

[jak1389]

sounds like rinfs, but i doubt its your vavles, if anything it would be vavle seals. time for a tope end rebuild, and replace to valve seals.

[yungair23]

ok so its rings and valve seals or eather one also i am thinking of putting a 416 kit in my 400ex and i am wondering will this kit fix my blue smoke problem and where can i get a 416 kit?

it isnt as easy as a kit. you need to have the piston sleeve pushed out and the new one pressed in.

[prepracing]

Originally posted by mittimj
it isnt as easy as a kit. you need to have the piston sleeve pushed out and the new one pressed in.
Thats a big negative, you do not need a new sleeve to bore to a 416. If you have it bored to a 416 you will have new piston and rings, and have whoever does it put in new valve seals ( also check valves for wear) and replace if needed. Then yes your smoke problem should be taken care of and also bump up your power :macho C & D racing on this site seems to be a popular place to buy/order these parts, any local machine shop where you live should be able to perform the work once you have all your parts.

[F-16Guy]

I would go with a 406 (.040" over), it will leave you more cylinder for the next rebuild. Buy a .040" over 11:1 piston (JE, Ross, Wiseco; your preference), and an OEM (Honda) top end gasket set for an XR400. Take the new piston, cylinder, and head to a shop and have them bore the cylinder (about $50), grind the valves and install new seals (probably $100), and grind the rings to the proper gap ($10-20??). After that, you'll have a ready-to-assemble top end with no guess work. It's really not worth it to cut corners on stuff like this.