Not impressed w/ 4 stroke yet... HELP!!!

[stuntman_12]

Just bought an 02' 400EX that was still apart from the jug up. It has a new piston, rings, and it got rehoned... I went by the books and put her back together w/ out a problem. I pulled it down the road try and start it more aggresively and it firers around everyother combustion stroke then blows smoke like crazy. Then i realized that oil is some how getting in the chamber AND oil is coming (a lot of oil ) out the front of the motor (around the exhaust) some how?

I wanted to go 4 stroke to get AWAY from this! I've torn this thing down twice... the oil rings are perfect and so are the compression rings. Gaskets are good too?????????:mad: :mad: :confused:

[bwamos]

1) What brand head gasket did you use? Some are total crap on the 400ex. Most prefer the Cometic XR400 gaskets.

2) Have you done a compression & leakdown test?

Something definatley isn't right. Probably something simple. It usually is.

[stuntman_12]

i think they are cometic... the quad has those stickers on it and the gaskets are metal and appear to be new also...

[GPracer2500]

"...that was still apart from the jug up...", sounds like maybe you bought someone else's problem child?

With more information about what's happening we can help narrow down what the problems might be....

[stuntman_12]

I know the quad ran fine about 3 months ago... it was pulled apart to rebuild b/c it smoked alot. He put an oem piston and rings back in it and then wanted to put wiseco stuff in it. So it sat there COVERED UP in his garage until i bought it. Now i have this oil problem??? What other info can i get you? Comp check may help... what else?:confused:

[khen]

So a standard bore piston was put back in with just a hone and no bore? Was the piston to cylinder gap measured to be within tolerance?

[stuntman_12]

I haven't Officially messured it w/ a gage filler, but i have rebuilt A TON of other motors (mainly two stroke) and it has less than .015 play in the jug. I could BARELY push the piston side to side. The rings stood pressed firm against the edge of the jug...

are yall stumped too?:confused:

[khen]

hmmm.. So were the valve guides and/or seals replaced?

[stuntman_12]

nope... i thought about that too.. but that shouldn't cause oil to come into the chamber at the rate it is... I firmly believe that if it weren't for the oil in the chamber that this thing would run like a top... The automatic pressure release spring in the head and under the cam isn't there... could this affect it? I asked a buddy of mine that is also missing his and he was riding his 400... so i'm LOST:mad:

[khen]

I agree, the valves would have to be pretty sloppy in the guides for that rate of oil to enter the cylinder.. The decompression mechanism isn't required for it to run.

Are you sure that the center oil ring isn't overlaping itself?

[stuntman_12]

Well, i stripped her down to the piston yesterday to check that... i got my dad also to check it out. We both agreed that it was all straight.. i used my fingers to compress the rings back in.... it's ALWAYS worked before... the oil ring comprised of the first "flat ring" then the "wavy ring" and then the last "flat ring" were all tightly snugged into position around the bottom of the piston.

I personally think that oil is... well hell, i don't have a clue? I'm no certified mech. but i'm not stupid either and i can't figure this out.

[khen]

The expander ring (the wavy one in the center) can't overlap itself or it could cause problems. It needs to be touching end to end but not overlaping.

I can't think of what else could be the problem.. There are only so many ways oil can enter a cylinder.. :confused:

[stuntman_12]

From your sig it appears that you know what your talking about... well... i guess i could tear it back down AGAIN and triple check to see if the ring is touching end to end. It appeared perfect yesterday? Is, what other way is there for oil to enter the chamber? When it is, HOW is it leaking from the front of my motor????

[GPracer2500]

Warped heat?
Cylnder out of round?

Just throwing out ideas...

[2muchquad]

Oil could be coming from your base gasket.Look at your valve seals also

[lqtrax]

have you checked the head for cracks ? Seems like I have heard of that somewhere about 400exs. like I say just a thought.

[stuntman_12]

Well if there are any cracks then they are hairline... I gave up and i am taking the piston, jug, and head to a shop to get the piston tightness, cylinder roundness, and valve stems checked. So that should tell me my prob. Then i can learn how to fix it. I attempted to get out the cheap way by purchasing a quad that "Just needed put together" IT was from a friend Too!!!

You win some you lose some....:ermm:

[stuntman_12]

GOT IT!!!!!!!!!! it's gonna cost me though... my "buddy" thought that he could just throw a new piston and rings in, do a half *** hone job and then bam!!! it run... nope... there was too much play around the piston... so what the biggest kit i can that will fit in my stock sleeve? 407? or can i go 416?:rolleyes:

[khen]

Cool that you figured it out.. For the stock sleeve you can go 406, 416 or 426. If I were you I'd go with a 406 or 416 and leave an extra bore or 2 in case you need it down the road. The power difference between the 3 isn't that much.

[Iliketogofast]

Not being impressed with 4 strokes is a common problem. As a matter of fact, it happens all the time!

There's only one solution, and I think you know what it is. :D