400ex smoking bad 5 hours after rebuild

[riley1374]

Hey Guys,
Rebuilt to a 406ex 11:1 and added a stage 2 hot cam. Ran good, no smoke or issues. Yesterday we go out, and my buddy pulls me over and says your smoking like crazy. My low end jetting is off a little since it was still jetted from the cool season, running rich, but the smoke appears to be white with a blueish tinge to it. I am racking my brain on this one. Any idea what it could be? When it started smoking, it did not change the way the bike ran at all. I do not see any leaks down by the head gasket. Also, it looks like the exhaust was spitting out either oil or gas. Ughhh, please help.

[Scro]

Sounds like you may have an issue with your rings. I would pull the head, and inspect the cylinder walls. If a ring is causing that much smoke, it's likely that it scuffed the cylinder walls. Other possibility is valve seals. But that is usually a problem that gradually progresses, and not just lets go all of a sudden. Atleast from my experience.

[Honda.rider5871]

Did you have the cylinder bored and honed for the new piston and rings? if not you wont get a good seal

[DragonGunner]

Hey Guys,
Rebuilt to a 406ex 11:1 and added a stage 2 hot cam. Ran good, no smoke or issues. Yesterday we go out, and my buddy pulls me over and says your smoking like crazy. My low end jetting is off a little since it was still jetted from the cool season, running rich, but the smoke appears to be white with a blueish tinge to it. I am racking my brain on this one. Any idea what it could be? When it started smoking, it did not change the way the bike ran at all. I do not see any leaks down by the head gasket. Also, it looks like the exhaust was spitting out either oil or gas. Ughhh, please help.

Running lean can fry your rings....but u think you were running rich, but running rich in cold can convert to lean when warmer...like to know what you had your jets at...? My 406 ported 11:1 web cam k&n open airbox white brothere e series runs 185 main 42 pilot needle raised one notch.....this is good to go for warm weather....too lean for cold.

[riley1374]

Running lean can fry your rings....but u think you were running rich, but running rich in cold can convert to lean when warmer...like to know what you had your jets at...? My 406 ported 11:1 web cam k&n open airbox white brothere e series runs 185 main 42 pilot needle raised one notch.....this is good to go for warm weather....too lean for cold.

Everything was professionally bored and honed by a reputable shop. New valve guide seals also. As for jetting I am running 180 main, 42 pilot and needle raised one.

Dragon gunner, I thought cold weather required richer jetting and warm weather required leaner jetting then weather. Still dont know what went wrong. CHecked my exhaust when i got home and it is definetely oil all gummed up in my discs on exhaust.

[Blodg]

Is it possible the rings were installed upside down although I don't know that it would cause it to let oil past. Maybe a valve stem seal fell off? Definitely going to need to tear into it to see what the problem is.

That sucks, I am about 3 or 4 hours of ride time on my rebuild and I can't imagine having to deal with a problem like this so soon.

[DragonGunner]

Everything was professionally bored and honed by a reputable shop. New valve guide seals also. As for jetting I am running 180 main, 42 pilot and needle raised one.

Dragon gunner, I thought cold weather required richer jetting and warm weather required leaner jetting then weather. Still dont know what went wrong. CHecked my exhaust when i got home and it is definetely oil all gummed up in my discs on exhaust.

Correct on richer for cold weather because the air is denser...intead of jetting richer I throw a lid with holes in it to cut down on the denser
air and it richins up about right. Check your oil level also.....getting too low will fry something also.

[Thumpin440ex]

Post a vid of what your calling bad smoke. Very easy the rings have not seated all the way.


John

[Honda.rider5871]

Did you stagger the rings gaps? if you lined them all up oil can get through that way also

[Blodg]

Maybe you are on to something Thumpin, I wonder if maybe the rings/cylinder could be glazed over? Although that shouldn't cause "bad" smoke I wouldn't think.

riley, what kind of break-in did you do on this rebuild the first 30 min or hour it ran?

[Thumpin440ex]

Maybe you are on to something Thumpin, I wonder if maybe the rings/cylinder could be glazed over? Although that shouldn't cause "bad" smoke I wouldn't think.

riley, what kind of break-in did you do on this rebuild the first 30 min or hour it ran?

My bike was so tight after the rebuild it took me 3 dead batteries attempting to crank it over normally, lol However it smoked a little bit but nothing excessive IMO. I heat cycled the bike for about 25-40 mins then ran the hell out of it. Some times it takes a bit for rings to seat..Sounds like the jetting is close. But being to rich can glaze the cylinder. I would run the bike some more and see if it goes away. Check the oil for excessive gas smell, change it if it smells like gas.

John

[chevella]

I had the same issue after one of my rebuilds. I had about an hour run time when it started smoking like a freight train. It turned out that both intake valve seals had pulled off the valve guides. I attributed it to the cheap valve seals that I used. I replaced them with Honda seals and haven't had a problem since.

[powerbomb400]

Had the same problem using aftermarket valve guide seals. Put Honda seals in problem solved.

[riley1374]

Had the same problem using aftermarket valve guide seals. Put Honda seals in problem solved.

That has to be it. Still have not had time to rip it apart. Thanks guys