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myr1hatesme
05-24-2009, 05:59 PM
Me and my friend both have 400ex's. His is a 02 and mine is a 04. The problem is both are starting to smoke. His is alot worse than mine. We did a topend rebuild on his ( new piston,rings,gaskets,ect). His is still smoking pretty bad. We have only ran it about 15min. Should we run it longer to see if it will stop? I'd like to get it figured out before we do mine.
brian76708
05-24-2009, 06:05 PM
Originally posted by myr1hatesme
Me and my friend both have 400ex's. His is a 02 and mine is a 04. The problem is both are starting to smoke. His is alot worse than mine. We did a topend rebuild on his ( new piston,rings,gaskets,ect). His is still smoking pretty bad. We have only ran it about 15min. Should we run it longer to see if it will stop? I'd like to get it figured out before we do mine.

did u do valve seals does it only smoke when you first start it up. and if its just after the build of course its going to smoke more because of all the excess oil you put in the cylindar when putting it all together. Also if you re ringed it did you get the cylinder honed if you didn't this could be your problem cuz the rings need to seat to the walls and with out honing the cylinder they wont.
myr1hatesme
05-24-2009, 06:09 PM
we didn't do the valve seals and we didn't hone the cylinder it looked pretty good. We might take the head off and do the seals but the jug looked real good
racer 557
05-24-2009, 07:37 PM
my 06 has same problem i was told that its a honda just triple check oil i was thinking rings were going bad but i have no clue
timmy400exfast
05-24-2009, 08:52 PM
yea sounds like seals the same thing happened to me to i just got it rebuilt everything but the head and one of the exhaust valve seals went bad
racer 557
05-24-2009, 09:06 PM
mine only does it on hard decel like real high rpm to letting off all way but does not do it at all on accelartion
brian76708
05-24-2009, 11:56 PM
Originally posted by myr1hatesme
we didn't do the valve seals and we didn't hone the cylinder it looked pretty good. We might take the head off and do the seals but the jug looked real good

honing is not only to repair the cylinder it is used to aid in seating the rings. and if it only does it after start up then its probably just the valve seals.
hypersnyper6947
05-25-2009, 12:44 AM
have your head serviced, valve seals etc... its relatively cheap and should fix your problem
myr1hatesme
05-25-2009, 05:57 PM
ttt
Which 450?
05-25-2009, 07:16 PM
hoping for an easier answer?
myr1hatesme
05-26-2009, 06:18 AM
pretty much lol. Thanks for all the info guys
myr1hatesme
05-26-2009, 06:19 AM
Originally posted by Which 450?
hoping for an easier answer?

where you at in maryland? I'm in southernmaryland, calvert county
Which 450?
05-26-2009, 06:22 AM
Im in white marsh, one thing to think about, if the smoking doesnt start till the bike is warm, it could be old oil in the pipe burning off. When does the smoking start? also, if the bike smokes after it warms up it is most likely NOT valve seals. Smoking at start up is valve seals. Oil sits in the head when the engine is stopped and oil drips down through the valve seals, then burns when the engine is first started.
myr1hatesme
05-26-2009, 03:40 PM
it smokes on start up. Mine right now only smokes on deceleration
Which 450?
05-26-2009, 06:59 PM
smoking on startup is probably the valve seals, smoking on decel is rings, probably because you didnt hone the cylinder.
Which 450?
05-26-2009, 06:59 PM
btw if you ever need a hand, I work on bikes, quads, scooters, trailers and such on the side.
myr1hatesme
05-28-2009, 07:37 PM
update: did the valve seal all smoking gone running great now. Thanks for all the info. I'm gonna do my bike tomorrow