400ex smoking at startup

[crazyelece]

Ok, last spring I traded a couple jetskis for a 2001 400ex. Soon after the trade I noticed the engine was smoking out of the exhaust. After some testing I determined it was burning oil. Due to lack of funds I had to ride it this way for about a month. When I finnaly got some money I rebuilt the top end of the motor myself except for rings. I replaced all the engine seals and put in new valve guides. When I took the top end apart it was aparant that the cause was a valve guide or valve guide seal because there was carbon buildup on the piston under one of the valves. I should also note the reason for not replacing the rings was that I did a compresion test and it tested at 100psi. After the rebuild it didn't help. It was still smoking horibbly and I could only think that somehow it was the rings or the piston. I figured it would take awhile to work on myself and I thought it was a little above my skills so I sent it to a shop. I had it rebuilt and bored .1 over. After it came back it was fine for about a month. Then soon after the first oil change after break in it started smoking again but this time just after startup until its warmed up. The guy who did the work is a pro class rider and a reputable builder and both of us are puzzled as to the problem. He suggested running fully synthetic oil (I think it was Klotz) but I couldn't find a dealer very close to me who supplied it so I switched over to Honda synthetic blend oil. I have heard synthetics don't let the rings seat in and this may be the cause but I'm unsure. I just was wondering what others thought the cause might be. Its not really bugging me except it fouls out a spark plug every other month or so. I have been checking the level of the oil and it seems to stay fairly constant. I need to add a little usually every time a spark plug fouls. Any thoughts or suggestions would be greatly appreciated.

[nosliw]

when your breakin in an engine you want to use dino-based motor oil. lets the rings seal and walls to get properly scarred up. fully synthetic, while great any other time, is no good for break ins.

just my .02

[85atc350x]

It is possible to have good compression, But still have a oil burning problem. The compression ring may have properly seated, But the oil ring may not have. If that is the case you will have good compression, But will be getting oil through the oil ring and into the combustion chamber.

[crazyelece]

It doesn't seem to be a ring now. It seems to me it would have to be a drip or something because it seems to build up when the quad sits and then burn off when it is started. Is it possible to get a leak through the rings with the engine off?

I was also skeptical when the guy told me that break in with synthetic wasn't a problem, but he rebuilds quad engines all the time and does it to all of them. I think I am going to run regular oil this next time I change it and see what happens. I hope it is as simple as the rings haven't seated all the way.

[hondardr4life]

The same thign happens with my 330 big bore. It will spit out blue smoke when I start it, but when it gets warm its stops and doesnt smoke at all. I think its just a problem of the rings not being set also, but I am not sure:confused: .

[DirtDevilBT]

VALVE SEALS!!!

It has to be the seals. When it sits the oil runs down the valves and drips into the cyliner. Are you sure the seals weren't damaged during installation? The valve guides you put in, are they right? Did you heat the head up, push them out, and put the new ones in? Did you have to ream the guides? Were the vavle stems damaged at all?

If it were the rings I would say it should smoke all the time, not just on start up. If the rings are bad then the oil should show signs of contamination, the result of blowby. Does the piston have 2 or 3 rings? It's hard to imagine good compression but poor oil scraping. Strange

Lets try this for now.

[crazyelece]

Long story short - I tried replacing the valve guides the first time myself and ended up screwing up the head. So I had to get a new head with new valves. At that point I let the profesional do it so I imagine he reamed them. I know he removed, cleaned, reamed, and relapped the valve seats. I was considering valve seals but they are brand new so I don't really see them getting messed up so soon. I have thought about opening the head up again, but I think for now (if it is something in there) I am going to just keep replacing spark plugs cause they only cost a couple bucks a pop.

[DirtDevilBT]

Did you buy the head new or used? If the head was used I hope it doesn't have a crack in it. It sound like you don't mind the smoke for now. When you do decide to do something about it, take the head off and replace the seals. Use a peice of straw and slide it over the tip of the valve stem, put the seal on over the straw and on the stem. Remove the straw. This is the absolute most definate way you will know if the problem is with the seals. Hey, seals aren't that expensive, and you said you don't mind the smoke. lol, try it. At least you know you have covered all grounds to make sure it's not the 2nd of two enemies. I'd much rather spend a lot of time making sure it's not the head, than spend lots of money on a new bore and piston. Of course, you could always try new rings lol. Mine as well.

[hondardr4life]

I still just think that it is the rings not set yet. I had a couple people tell me that this happened on their 416kit. They said it went away with 3-4 tanks of gas. It doesn't take mine long to stop smoking, maybe a minute or so of idleing. If you want a little more info, do a search for the post, Is my quad supposed to do this??

[DirtDevilBT]

:confused: How many tanks have you ran and how many hours?

[crazyelece]

Maybe 2 or 3 tanks of gas. I usually top it off all the time so its really hard to say. I might have a total of 20- 30 hours on the engine after rebuild. With three oil changes. The first was Klotz full synthetic directly after rebuild. Changed after 5 hours idle break in and 5 hours riding break in (so 10 hours together). Next oil change was a synthetic petrolium blend with synthetic Lucas oil stabilizer added. I ran this oil for 10 to 20 hours then changed to synthetic petrolium blend with regular Lucas oil stabilizer. The quad only has 2 to 4 hours on it since last oil change.

[red2004 TRX450R]

U let it idle for 5 hours with synthetic to brake it in?
WHY


I will bet that the rings will never seal. in less u get it re honed (not bored) and put in new rings and use real oil and go out and run the heck out of it.

[DirtDevilBT]

Originally posted by red2004 TRX450R
U let it idle for 5 hours with synthetic to brake it in?
WHY


I will bet that the rings will never seal. in less u get it re honed (not bored) and put in new rings and use real oil and go out and run the heck out of it.

Yeah, I really hope that's not it either. Try going to a 10w30 petrolium based oil and run the hell out of it. Maybe, just maybe you can still get the rings to seal better. Basically, it sound like the rings seated without breaking in and sealling correctly. You could try the honing with new rings but that can be tricky if the bore wasn't tight to begin with.

[hondardr4life]

Hold up, now are you guys saying to run the hell outta it for break in? I am running the regualr Honda GN4 10w-40 oil. I may have 10 hours on it by now, and mine still smokes when i start it for about a minute until it gets warm.

[crazyelece]

The guy who rebuilt it let it run for about five hours (one full or almost full tank of gas) and while it was running would rev it every few minutes. He said he always does this to start the break in process. I trust him I know quite a few other people who have had him rebuild their engines and a bnch of them were 400exs as well. When I got it back I rode around the trails I have and probably put another 5 hours on it before I changed the oil.

[fitethesystom]

Air cooled engine idling for 5 hours = engine burns up

Probably Not a good idea.