Opinions on why my 400ex smokes??

[sleepin400]

01 400ex, I did a wiesco 11:1 piston .040 over, and I have a stage 2 hotcam. Durring the project, I had the head ported, and new Honda valve seals installed.


It smokes:

more at 1/2 to 3/4 throttle

When I had to toe a buddies bike it smoked like crazy.

After 30 min or so of riding steady, it will smoke quiet a bit less.

Opinions:

My Theory.... I the rings are washed out.

Not convenced yet its the valve seals.

let me know what you guys think.

[TCracin440ex]

its your rings...you have to rebreak them in...its gonna smoke for a lil while then when it gets hot it should stop..

[trxkruzoffman]

what kind of pipe do you have on there, a friend of mine has a white brothers e series on his 400ex and it used to smoke but it was just the packing, or you might need to rebuild it,

[TCracin440ex]

he stated above he just finished a rebuild....its just your rings they aint seated yet...give it a little while they will eventually seat and no more smoking

[400exstud]

my $1000 beater truck does the same thing. 1 puff of smoke when you fire it up and that it. I figured it was the rings. Just a little more lubrication:p.

[LeGaCyGiAnT124]

yea man its your rings, i got a rebuild and it smoked for like 2 rides then its fine. Change your oil more often!

[RiderTRX400ex]

yup rings sound liekt ehy havent seated yet, smoking on startup could be mostly your valve seals

[FoxMxRiders]

If it smoke when the motor its cold,this is your valves seats

If it smoke all the time it propably your rings

But let your ring seat correctly and you will see if it really smoke

[tater_kamik]

because its a honda





did you set the rings apart where the breaks are in them so that they are not all in a line?

[sleepin400]

what kind of pipe do you have on there, a friend of mine has a white brothers e series on his 400ex and it used to smoke but it was just the packing, or you might need to rebuild it,

I have a full system Yosh on the bike, it has a few years on the exhaust, I never thought about that. I do get quiet a bit of sought (spelling) wet black resen on the exhaust tip.


yea man its your rings, i got a rebuild and it smoked for like 2 rides then its fine. Change your oil more often!

I should of added this. I've had quite a few hrs on the bike scince the rebuild, like 20+ The bike ran fine as of about a 2 months ago, when cold, it would smoke...kinda wierd. Then one day we went to a track was riding it around shut it off. And Bam, when I restarted it smoke :confused:
Ever since Its smoked like I explained.



my $1000 beater truck does the same thing. 1 puff of smoke when you fire it up and that it. I figured it was the rings. Just a little more lubrication.

LOL, yeah, on a beater truck I could live with it. But I'm smoking out my friends lol, plus I'm thinking about selling it in the near future so I'd like to work the issue out.


did you set the rings apart where the breaks are in them so that they are not all in a line?

Yeah, my buddy has is a mechanic, and has rebuilt quite a few of these. I'm sure we put the rings in correctly, plus as I should of mentioned before. I have had it running for a good while w/o smoke.

Thanks for all the replys. I'm getting pritty convenced its the rings. I guess can I just re-ring the bike??

It would kinda suck to have to get a new piston set. And even more suck if I had to re-bore the cylinder.

thanks again

[xc400ex]

When I raced a 400ex I rebuilt it 3 times in one year. 400's will smoke so get used to it. Not one speck of dirt ever reached the motor, and was always broke in on non synthetic oil and it was changed often. I just rebuilt my brothers 400 with a JE 416 piston, about 15-20 hours it smokes an burns oil again. Oh well just add oil to em and ride.

[balls2da-wall]

I have a 440 and have rebuilt it 3 times as well...mine has never smoke except when i tryed running mobile one red cap oil in it(full sythetic) thing would smoke like crazy until it was warm then it would calm down..switched back to semi-synthetic and it never smoked again....400's are not supposed to smoke or burn oil!!! maybe a tiny bit but not enough to notice!!!

[xc400ex]

Thats good that yours doesnt smoke, but I can honestly say I have never saw a 400ex around here thats rode in the woods that doesnt smoke. I raced mine for a year in 4 stroke and open A harescrambles and I would still be racin it if the motors would hold up.