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Rebuilt still smoking?
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Posted by: Westro

honed the cylinder and and put new rings in. New gaskets and new seals on the valve guides.

Fired it up and it is still burning oil. Any ideas on what I missed. (I rebuilt it because it was burning oil)

Posted by: 400exbiggun

i only have 2 guesses.

#1 The rings didnt set yet and are not making a perfect seal until they do set. thats why you do a comp check sometimes. Right after the topend and you can actually see the comp increase as the rings seat.

#2 Did you mic the cylinder to make sure that you have enough room and didnt need a bore?

Sorry but thats all i got.

Posted by: 2004exrider

ya, sometimes you can get away with just honing, but in your cases it sounds like it needs bored.

Posted by: 024ooex

I'd say adjust the valves

Posted by: limetimeracerII

If it is just puffing a little smoke, I'd wait till it breaks in and see if it goes away before you tear into it. I work at a bike shop and even brand new ones smoke a little bit. Plus I just rebuilt mine and it did the same thing but it eventually stopped after I rode it a couple times.

Posted by: Westro

no it's not puffing a little bit but is burning blue all the time. I have broke the motor in and it is still burning. about 40 minutes of riding

Posted by: TRXRacer1

What did the cylinder measure out at, was it within specs to just put rings in? How did you check it?

Posted by: MXRACER86

I hope you replaced your valve seals!!!! I am 99.9% sure that you need new valve seals!!!

Posted by: AtvMxRider

quote:
Originally posted by MXRACER86
I hope you replaced your valve seals!!!! I am 99.9% sure that you need new valve seals!!!

Posted by: 400exbiggun

quote:
Originally posted by Westro
honed the cylinder and and put new rings in. New gaskets and new seals on the valve guides .

Fired it up and it is still burning oil. Any ideas on what I missed. (I rebuilt it because it was burning oil)

Thats what he said.

Posted by: ReconRider25

did u line up the rings right? if theyre not in the right spots(should be staggered like) itll burn oil....

Posted by: Westro

Valve seals.. hum been through that.

And the rings are staggered.

Could the head gasket be leaking and sucking oil?

Posted by: TRXRacer1

LOL, you didn't measure it did you?

Posted by: Chino886

Hey Westro,

I don't mean to post on your thread, but I am rebuilding right now and I want to avoid this problem. How do you measure the cylinder to make sure your piston will fit? I am installing a stock bore JE 10.5 piston.

D

Posted by: Westro

I own a micrometer and it was used.

I was hoping for some useful information. This is my 54 year old father’s 400ex and he hasn’t beat the thing. It has been smoking since late last year. So this spring I rebuilt it and it’s the same (smoke wise)

So is this a common thing with the 400ex? I guess I should just ditch this thing and stick with the 2 strokes. He has been taking a shining to my stage II Scrambler that I beat when my R is down.

Not real impressed with it and now the oil burning…… Anyone NEED an oil burning 400? Completely stock minus the twist throttle.

Chino886, mic it out. The boys around here should help you out with tolerances.

Posted by: 400exbiggun

Well there is something wrong here. Quads dont just out of the blue leak oil onto the piston to burn. Its either the bore, rings/piston, valves or seals or headgasket. Something is not right. When running right there will be very very minimal smoke if any at all (shouldnt really smoke at all) from 4 strokes. Did you do a comp check after the rebuild? try a leakdown also.