'01 400ex smoking like crazy

[jcole1988]

new piston,rings,valves,clutch cable, spark plug,grips,tires,etc... smokes terribly, does anyone have answers?

[CJM]

did you replace the valve seals?

when you did the rebuild did you make sure the rings were properly spaced and they shoulda been tight into the cylinder

What color is the smoke? blue, white?

[aDviSol2y]

Originally posted by jcole1988
new piston,rings,valves,clutch cable, spark plug,grips,tires,etc... smokes terribly, does anyone have answers?

It's the new tires and grips that made it smoke! :devil:

[tri5ron]

Was the cylinder honed prior to the new piston?
or was it bored?

Was it within spec?
Did you measure it?

Are you the original owner?
Or do you know the maintaince and useage history of the bike?
(was it Raced?, Trail ridden?, Adult or kid owned before you?)

Was it possibly bored oversize before you got it, (i.e. 406,416,426,etc.), and could you possibly have the wrong size piston/rings in it?

Did you do the work yourself?
Or did you take it to a machine shop, and have THEM measure/hone/bore/install the piston and rings?

Were the new valves and/or valve seats reground? or lapped?

Was the head ever overheated?
Was it checked for cracks?

I'm sure there are other questions that need to be answered, but if you can answer those, we would be better able to give you some experienced, and more educated advise.

BTW, Welcome to the forum.

There are alot of friendly, helpful, and knowledgeable folks here that will be more than happy to help.
(but we do also like to joke around some, so don't take it personally).

[beags86]

Originally posted by tri5ron


BTW, Welcome to the forum.

There are alot of friendly, helpful, and knowledgeable folks here that will be more than happy to help.
(but we do also like to joke around some, so don't take it personally).

there are alot of good guys on here, but ron is not one of them, don't listen to a thing this guys says!!


- just messing ron.

ron is right, a little background info would be helpful here.

[tri5ron]

Originally posted by beags86
there are alot of good guys on here, but ron is not one of them, don't listen to a thing this guys says!!

- just messing ron. :D

[jcs003]

did you do a leak down test after rebuils?

did you do a compression test?

are the rings installed correctly? its is possible to have them in the correct order, but be upside down...

[jcole1988]

I didn't do the work myself so i don't know if the rings are upside down or if it was honed. the owner before me said that it was at stock bore though. my guess was the valve seals but im not 100% sure. The smoke is blue and white, and theres alot of it. it doesn't smoke right when i start it though it begins about 30 seconds afterwards.

[aDviSol2y]

Blue smoke means oil. Most likely bad/incorrectly installed rings.

[aDviSol2y]

Oh, by the way, welcome. And yes there is a lot of good information on this site, and yes we do joke around a bit. Life would be no fun if we were serious all the time. :D

[VTredneckgames]

yeah if it is smoking after start up at an idle, then it is in the rings

[TRXRacer1]

Most likely the previous owner didn't know what he was doing and it's ready for a bore. If it's after you've ran it for 30 seconds then it is NOT valve seals. You have a cylinder issue.

[jcole1988]

does that mean it HAS to be bored or can it be just honed? And if it does have to be bored, what would you recommend, I don't wanna bore it too much incase it will have to be bored again.

[tri5ron]

Originally posted by jcole1988
does that mean it HAS to be bored or can it be just honed?

This will only be determined AFTER you take the piston out, and the cylinder off. It needs to be measured to see if it is still within spec., as well as to see if it is straight and true. This needs to be done by a competent machine shop, or somebody with the proper tools and experience.


And if it does have to be bored, what would you recommend, I don't wanna bore it too much incase it will have to be bored again. [/B]
Again this will be determined after it is measured. Readily available oversize bores/pistons come in 406, 416, 426, 440. They also come in compression ratio's that you will need to choose what you want, ranging between 10:1 to 12:1, I recommend staying at or below 11:1 so that you can safely run pump gas, and not be limited to exotic blends of race gas.

Another thing to consider is depending on which bore/piston, AND compression ratio you choose,... You MAY want to consider changing the cam to be the most compatible, to you riding style, and at what point in the rpm range you want the most effective power band.

[tri5ron]

Originally posted by jcole1988
I didn't do the work myself so i don't know if the rings are upside down or if it was honed. the owner before me said that it was at stock bore though. my guess was the valve seals but im not 100% sure. The smoke is blue and white, and theres alot of it. it doesn't smoke right when i start it though it begins about 30 seconds afterwards.
You have to ask yourself,...
"why would a relatively low rpm engine, need new rings, yet still be at a bone stock bore"?
This indicates a few possibilities to me.

1- The previous owner wore the darn thing out, and possibly even overheated it too.

2- He was probably not highly experienced in engine rebuilding, and just slapped a new set of stock rings in it.
(and maybe even upsidedown too).

He may not have even measured the cylinder to see if it was oversized, barrel shaped, or worse yet,... deeply scored or cracked.

Another possibility could be a cracked head.
(Lets hope not),.... BUT you MUST have it properly checked to be sure.

Look at it THIS way,...

You now know that something is certainly wrong in the top end of the engine.
You ALSO know it HAS to come back apart to be corrected.

SOOoooo,.... this means that you DO NOT want it to be screwed up for a THIRD time, and it needs to be done RIGHT.

Another couple of questions that you need to ask yourself are...

" How well do I know the previous owner",.....
"How well did he maintain his equipment",.....
and,
"Why did he REALLY want to sell it in the first place"??

BTW,....
How much did you pay for this quad ???
(a really low selling price might also give you some indications to the answers, for the above asked questions).

[TRXRacer1]

jcole1988, no matter who posts next just remember tri5ron just gave you pure gold. Every word he put up is 100% correct. You will need to get in this motor and have it properly measured before you know where you are.

[CJM]

Originally posted by TRXRacer1
jcole1988, no matter who posts next just remember tri5ron just gave you pure gold. Every word he put up is 100% correct. You will need to get in this motor and have it properly measured before you know where you are.

x2 on rons advise, its golden.

[jcs003]

Originally posted by TRXRacer1
jcole1988, no matter who posts next just remember tri5ron just gave you pure gold. Every word he put up is 100% correct. You will need to get in this motor and have it properly measured before you know where you are.

x3. and definitly dont ride it anymore. hopefully your crank and crank bearings are still good.

[VTredneckgames]

and while it is apart, have the head checked, valves ground, and install new valve seals. Plus throw on a new timing chain.

[sc400ex_rider]

just tear it down and check everything that yahoo done. some thing is obviously wrong and could be catastrophic.

[barton1398]

Check and see if it is puking oil out of the engine breathing tube going to the little white resivor on the side of your air intake it sounds like this is what is happening to me. After 20 or 30 seconds of running the resivor is filling up and being sucked into your intake making it smoke. If so it could be one off a few things it could be as simple as too much oil in it or it could be wrong size piston or the worst it could be your cylinder has been egged out. The 400's are bad about egging cylinders. Good luck:confused:

[jcole1988]

if my resevoir is filling up, that must mean theres to much oil in it, which i've checked it and theres not, also i just had new piston and rings installed last winter along with a timing chain an new valves. i'm supposed to ride this weekend with a friend, will it hurt it to ride like this for a couple of hours before i put it up?

[jcole1988]

if the rings are upside down would that cause this? The guy who did the work was a little sketchy and im never going to him again.

[jcs003]

Originally posted by jcole1988
if the rings are upside down would that cause this? The guy who did the work was a little sketchy and im never going to him again.

what i know is if rings are not indexed corectly and or upside down it will make your rings wear out prematurely and possibly damage your cylinder/rings. also, blow-by is another issue. i personally wouldnt ride it.