my 400ex started smoking

[Slapasack]

ok so a few days ago i noticed my 400ex would blow smoke out of the exhaust after giving it a good rev when i first started it up but then wouldnt do it after it got warmed up until today when i was riding my friend noticed it smoking when i was in the higher rpm range but it wasnt a lot of smoke and i think my motor may have been like ticking or knocking so do my valves need readjusted with some new valve seals or is it the rings or what?

[UNBROKEN]

i would give it a compression test but just those symtoms alone arent good sounds like ull be needin piston/rings and valve seals at least but if u do plan on opening the motor u might as well do it right with new cam and cam chain and also rebore the cylender so nothing will be second guessed

[rideracelivemx7]

spend the 20 or 40 for a compression test. if its the stock motor it should have around 100-120 if its below lets say 100 then its your rings. but if you put out like 110 or 115 then you know its myour seals. you dont need to replace everything he said. you can always make do with whats there if your budget says so. but deffinetly check your cam chain and how loose it is.

[UNBROKEN]

well if u like ure quad and plan on keepin it and have the money u might as well rebuilt the top end , but thats my opinion

[02' trx400ex]

it could be your oil ring on your piston id get that checked out

[416exman21]

you dont need to replace everything he said. you can always make do with whats there if your budget says so. but deffinetly check your cam chain and how loose it is.


i agree -as long as your sleeve looks fine and the pistion still good just put rings on it .....(their's no reason to replace all that crap if you dont need it and the stuff in good shape)... mine has a lil bit of smoke when its cold ,but not real bad ...go buy you a compression gauge for bout $10 or $15 and start there.....and why you are doing that go ahead and get the filler gauge for the valves and check that too make sure it's at top dead center when your messing with the valves .....i would do that before tearing in to the motor.....

[quadmad16]

my 400 is only a few weeks old and it has started blowing blue smoke in higher rpm's but only after it has warmed up.:confused:
what could be wrong like its brand new..and totally stock...need help:ermm:

[scdirtdobber]

mine too

[honda400ex2003]

I sure am glad mine did not do that. you guys are having a heck of a time with your new machines smoking. mine took 3 years and the valve seals were going out. in your case slap that is what it sounds like for you. smoking on start up and under accelerations is valve seals most of the time. do a comp test to check out the rings and you can do a leak down test to see how good your valves seal. steve

[scdirtdobber]

I'm about 35 miles from where mine was built and know a few guys who work there,I can blame them for getting slack LOL!!:devil: Really though I think some issues come up after they made changes in 05,mine as you know is like quadmad16's 400 with a identical problem and have visited other sites with smoking issues especially the newer models.Must have been a bad batch of engines somewhere along the line

[honda400ex2003]

yeah something must have got messed up with some of them. sorry to hear that anyway, you know. it does suck but hey now you can mod it out faster. it is more fun to go for a year or two between some mods to keep it interesting instead of doing them all at the same time. lol, steve

[scdirtdobber]

Gotta make the best of it,I plan on a jet kit and a pipe in next month or so.If the smoke gets worse think I'll go with one of the BB kits on e-bay,at least if I do it I'll know it's right.May need some tips later on w/selection.With the price of the new 450cc & up I think I'll stay with the 400.Charles