Question

[400excaleb]

my 400 is smoking at deceleration and burns a lot of oil. im gonna change the rings and valve seals. how hard is this to do, and should i do n e thing else while i got the motor tore apart that could be causing this

[GOTFEAR]

new piston and probably new bore.

[honda400exr]

new seals and rings won't be too hard but you might wanna check the cylinder walls before you order rings..most likely you can get away with just honing the cylinder but if there are deep scratches or anything you'll need to bore it to the next size. you're better off checking that before you order rings for the piston you have now and then findout you got them for nothing cause you have to bore it. just a suggestion though.

[fastredrider44]

I agree. Mine was doin the same thing. I went to hone it and found out my cylinder was starting to form a slight oval shape. It wasn't bad, but I went ahead and punched it to a 426. I've always heard good things about that size.

[honda400exr]

forgot to mention that it would be a good idea to replace the cam chain with a heavy duty chain while the engine is apart especially if you're going to bore it out and run higher compression. Also check the tensioner and guides. The guides may need replaced if they never were.

Probably don't have to do all this but it's a good idea to go ahead and do it now while it's apart instead of a couple months after it's back together.