smoking... sometimes...

[BeefySTi]

so, my 400 will smoke bad, and when I say bad, it is like a diesel (except bluish white) when it has set for a couple of weeks or longer. When I let it set idling for a while, it goes away almost completely, maybe a little puff here and there. But if i start it a few days after I ride, it wont smoke at all. I went outside a few minutes ago to try to video it so I could post it and show you guys what it looked like, but no smoke whatsoever (I rode it Saturday). Why would it do that? The smoke also has a very pungent odor to it, almost like a dirty diaper smell to it (for those of you with kids, you will know exactly what I am talking about).

I recently posted about it stuttering when riding hard, and I changed my plug and cleaned out the carb, and that has all but vanished. It runs real strong, and pulls harder than my buddies 2004 does with a stage 2 cam, exhaust, intake and rev box (his is worn out tho).

If it was consistently smoking, I could probably figure it out by searching on here, but it isnt. Sometimes like a freight train, others, not at all.

Any takers? I know you mechanics and detectives will be able to figure this out!

[TheAwesomehonda]

My 426 does the same thing when I start it and it hasn't ran in a few days. But it goes away in 30 seconds of running. I would like to know what this is caused by to.

[dxcody]

Could be condensation built up in the exhaust packing.

??? Dunno.

Someone on here can tell you probably.

My 416 did that, mostly when it was cold out tho.

[CJM]

Valve seals could be worn out, letting oil slightly leak in. Could be excess carbon build up as well.

If it doesnt lose oil over time do not worry about it.

[BeefySTi]

usually oil level is right about where it was when i changed it. so if it is burning oil, it aint much at all. thanks for the reply

[quadracer556]

i cant remember the old addage but it was like smoke on start-up,bad valve seals.smoking on accel/decel bad rings.either way youre looking at one or the other MINIMUM.gasoline engines do not smoke like a worked diesel for no reason.what year is it?when was it re-done,if ever?if an air cooled is blowing smoke its burning oil,does not matter the color.its coming through somewhere.i had one like that last spring,blowing huge clouds of white smoke bad(i think it burned white because i had been running hard for around 2 hours and it just annihilated the oil when it came through).believe it or not a circlip broke off at about 1/4 inch and flopped back and forth through the wrist pin until it gouged both sides of the cylinder wall taking my 426 back to a 416.

[BeefySTi]

it is the one in my sig. It was supposedly bored over, to what I, do not know. I havent had a reason to tear the engine apart and didnt want to mess with opening it up just to find displacement. was done by the uncle of the previous owner who was supposedly a mechanic. It didnt smoke when I bought it, otherwise I would have walked. And also, it was my first ATV and i really didnt know what I was getting into. Call it a mistake out of ignorance.

That being said, I understand that if it smokes on start-up=bad seals, etc, but it isnt consistent at all. that is what is confusing me. if it sits for a long time, it will smoke on start up. and goes away after it runs for a little bit. If I start it up a few days after riding it, it might give a little puff or two, or maybe not at all. but it is nowhere near what it is like when it has sat a couple of weeks or more.

Can exhaust packing cause this? it is a pretty old muffler, and i have not repacked it and not sure when it was repacked last. (i know, i need to do it) I am just grasping at straws here, because of the consistency of the issue. usually if there is a problem with something, it will continue to be a problem, not just when it feels like being a problem...

[beastlywarrior]

Yep valve seals leak slightly and a bit of oil collects on the top of the piston

[TheAwesomehonda]

I'm not going to say don't worry about it :D but i don't think its that big of a deal. If it don't use oil, make weird sounds, have low compression (which you should check), or smoke all the time then it shouldn't be a huge problem.

[BeefySTi]

i am definitely gonna do a compression check at some point. just to be on the safe side.

. Yep valve seals leak slightly and a bit of oil collects on the top of the piston

First thing I have heard that makes sense to me... When it only sits a couple of days, there really isnt enough oil to smoke. so valve seals are probably the culprit... but yeah, I need to do a compression check too.

Thanks a lot guys!