Motor Rebuild

[Zeppelin03]

I stripped my 400 down to the frame today because im planning on replacing the piston and rings with a wiesco 11:1 piston. What i want to know is can i still run gas from the pump through it and are there any other things that are worth/should be replaced while the motor is appart.

[DieselBoy]

well definately inspect your valves. Do a leak test with kerosene, and if they are still sealing real good, there's not much else to do, except inspect your wristpin hole, rod spacing on the crank, and all that. you'll be boring it anyway so all you need other than that is to check your cam, your chain, your tensioner, your guides, etc.

and as far as i know, i think your machine will run fine on pump gas with 11:1.

[AR15 guy]

You should be fine with 11:1 as long as you can get 91+ octane in your area.

[400exrules]

what things should you look for on the cam chain to know if it needs replacing?

[dirtbikerider5]

if its loose. if the cam chain tightner is all the way out. i just put a new cam chain in mine. It was $88 from honda!!

[QUADBANGER305]

I JUST RAN MY HONDA 05' 400EX W/ NO OIL TILL IT TURNED OFF (NOT ON PURPOSE) IM PRETTY SURE I BLEW THE MOTOR BUT I WANNA KNOW HOW MUCH IT SHOULD COST TO FIX

[scruff_mcruff]

Originally posted by QUADBANGER305
I JUST RAN MY HONDA 05' 400EX W/ NO OIL TILL IT TURNED OFF (NOT ON PURPOSE) IM PRETTY SURE I BLEW THE MOTOR BUT I WANNA KNOW HOW MUCH IT SHOULD COST TO FIX

wont know till you get it apart. coulve just wiped out the crank and piston, couldve broke some tranny parts, coulve ruined your jug, coulve seized the cam in the head. if it shut itself off and was dry on oil, id say just start looking for an entire replacement engine.

[QUADBANGER305]

IT WAS BLOWIN A LITTLE SMOKE BEFORE I WAS KINDA HOPONG IT WOULD BE JUST A VALVE CUZ THE PISTON STILL TURNS OVER EASILY JUST FEELS LIKE NO COMPRESSION

[kalebarellano]

I am tearing down my 400ex too. I am boring to 406, and I plan to replace the valve seal that wears out commonly on the 400, I believe it is called a valve stem seal. Are those the seals that are tested with kerosene?

I am also replacing the cam chain with a crf cam chain, and I am painting the frame/subframe and a-arms as well.