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Westro
06-21-2005, 06:20 AM
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):confused:
400exbiggun
06-21-2005, 07:36 AM
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.
2004exrider
06-21-2005, 08:10 AM
ya, sometimes you can get away with just honing, but in your cases it sounds like it needs bored.
024ooex
06-21-2005, 08:29 AM
I'd say adjust the valves
limetimeracerII
06-21-2005, 10:34 AM
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.
Westro
06-21-2005, 11:19 AM
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
TRXRacer1
06-21-2005, 02:40 PM
What did the cylinder measure out at, was it within specs to just put rings in? How did you check it?
MXRACER86
06-21-2005, 05:25 PM
I hope you replaced your valve seals!!!! I am 99.9% sure that you need new valve seals!!!
AtvMxRider
06-21-2005, 06:15 PM
Originally posted by MXRACER86
I hope you replaced your valve seals!!!! I am 99.9% sure that you need new valve seals!!!
400exbiggun
06-21-2005, 06:44 PM
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):confused:

Thats what he said.
ReconRider25
06-21-2005, 07:11 PM
did u line up the rings right? if theyre not in the right spots(should be staggered like) itll burn oil....
Westro
06-22-2005, 04:24 AM
Valve seals.. hum been through that.

And the rings are staggered.

Could the head gasket be leaking and sucking oil?
TRXRacer1
06-22-2005, 07:55 AM
LOL, you didn't measure it did you?
Chino886
06-22-2005, 08:47 AM
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
Westro
06-22-2005, 09:03 AM
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.
400exbiggun
06-22-2005, 01:11 PM
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.:ermm: