400ex burns oil only with choke fully on

[laxman1306]

my 400ex will only burn oil with the choke all the way on...now if i back it off just slightly it will not burn oil... has anyone else had this issue?...and the top end has been rebuilt recently it had the same problem before the rebuild..new piston and rings, new valve seals and guides

[Pittsburgh400ex]

Huh?

You seriously ride that poor thing with the choke on?

[CJM]

How do you know its burning oil? You ride with the choke on all the time or something?

[laxman1306]

no i dont ride it with the choke i only have to use the choke when its really cold out just to let it sit and warm up till i can shut the choke off

[Pittsburgh400ex]

Ok so how do you think it's burning oil? If i let mine sit warm with any choke on it will spit some black if you rev it cause the plug loads up but oil is blue/gray. Choke would lean it out so you wouldnt get a dark black like it's rich either. I think you need glasses lol.

[JOHNDOE83]

Originally posted by Pittsburgh400ex
Choke would lean it out so you wouldnt get a dark black like it's rich either. I think you need glasses lol.

Actually, the choke richens it not lean.

[DragonGunner]

Choke on richens the carb, its getting more fuel and less air....it can load up on fuel and burn richer, plus its heating up the pipes and exhaust that usually in cold makes condensation......its more steam....then it warms up and doesn't steam smoke any more. I'm guessing its this and not burning oil.

[Pittsburgh400ex]

Johndoe: you are correct sir, lol. I went "derp derp" there transposed words or something i dunno, that's the point i was getting at though.

That or you broke a brand new ring or installed incorrectly. But i have done that to an old JE and it pours smoke.

[laxman1306]

no it is oil i can put my hand over the exhaust tip and i will have oil on my hand...the thing runs like a raped ape but its weird ...is it possible it has a vent problem?

[exrider12]

when you say you have oil on your hand, is it actually wet or is your hand covered in black soot?

[Longdong]

It could be excess grease burning off as the muffler bearings heat up......... :D

[fearlessfred]

yep you dont wanna over grease your muffler bearings.running low on red tail light oil is bad to

[Pittsburgh400ex]

What bore amd compression is your piston? I could gas my old setup and spary my hand with oil but it was obvious and very thick smoke. My problem was running a 12.5;1 on bad gas. It detonated, broke rings and cracked the piston skirt in 4 places. There are pictures of it on here somewhere.

[laxman1306]

its funny to read all the post from these know it all jackasses on this forum when you are just trying to get some insite from other people....i have built alot of different engines for atv's, bikes, drag engines for cars and high horse power turbo engines...i do know what i'm doing very well but i was only curious if anyone else has had this problem on a 400ex....like i stated earlier that it had the same problem before it was rebuilt....the day i picked it up it had this issue, it still does it im not to worried cause it runs great but id like to find the problem and its only when the choke is on when i let it warm up other than that it doesnt burn any oil and i know its oil not soot i know the difference...so if anyone has any real useful help and not **** head comments to post it would be greatly appreciated

[fearlessfred]

if it is not blowing blue smoke (black would be normal with the choke on) and its not using oil you dont have a problem. some oil does find its way into the combustion area thru valve guides and rings. the exess gas from choking washes all the oil clean

[Honda5]

just turn the choke off. bike fixed.

[CJM]

Were not jackasses. The problem is what you describe isnt oil unless something is out of spec or the valve seals are worn. What it is is gas b/c its too rich or the white smoke you see on start up choke or not is water condensation from the exhaust.

Blue (more or less graywish white) is oil, black/bluish looking is gas and pure white if cold is condensation.

[fearlessfred]

Originally posted by CJM
Were not jackasses. The problem is what you describe isnt oil unless something is out of spec or the valve seals are worn. What it is is gas b/c its too rich or the white smoke you see on start up choke or not is water condensation from the exhaust.

Blue (more or less graywish white) is oil, black/bluish looking is gas and pure white if cold is condensation. i admit that i can be a butthead, the mufflerbearing joke is is like a fart ,not everybody finds them funny.woman dont for sure

[laxman1306]

it is blueish white...its oil

[fearlessfred]

cjms description is probaly the best more or less graywish white and you can probably smell it

[exrider12]

Originally posted by laxman1306
its funny to read all the post from these know it all jackasses on this forum when you are just trying to get some insite from other people....i have built alot of different engines for atv's, bikes, drag engines for cars and high horse power turbo engines...i do know what i'm doing very well but i was only curious if anyone else has had this problem on a 400ex....like i stated earlier that it had the same problem before it was rebuilt....the day i picked it up it had this issue, it still does it im not to worried cause it runs great but id like to find the problem and its only when the choke is on when i let it warm up other than that it doesnt burn any oil and i know its oil not soot i know the difference...so if anyone has any real useful help and not **** head comments to post it would be greatly appreciated

Just trying to help bud. No need to get all defensive. If you already know that it's oil then its time to tear down the motor. The choke is irrelevant to the oil situation.

[CJM]

Have you physically verified after running it that its missing alot of oil? Compression or leak down test?

[MtnEX]

Choke is absolutely not irrelevant....

Having the choke on greatly increases the vaccum created.

The engine is sucking through a straw versus a 2" pipe basically.

Make sure it is not for some reason sucking it through the crankcase breather hose?


What work did you do to it?

[fearlessfred]

if the throttle blade or slide is closed the vaccum is the same wether the choke is on or not, if the carb has blade type choke on the air cleaner side of the slide than the vaccum is also created there ,but can not be any greater until the throttle is opened.if the choke is really an enrichment circut.than nothing changes with the choke on

[exrider12]

Originally posted by MtnEX
Choke is absolutely not irrelevant....

Having the choke on greatly increases the vaccum created.

The engine is sucking through a straw versus a 2" pipe basically.

Make sure it is not for some reason sucking it through the crankcase breather hose?


What work did you do to it?

Not trying to start an argument but how would this affect oil consumption in anyway? Im actually interested to hear about this.

[MtnEX]

When the piston goes down it is sucking harder than it would be with the choke open.

I just tried to put it simple like, think of a vaccum cleaner like a shop vac... you are sucking with the open hose, then you shove a crevice tool on the end.

If it has a problem where it can pull oil in the combustion chamber it might have enough suction to pull it on in with the choke closed and also not have enough air to burn it near as clean, so oil smoke would be more easily visible in either situation.

Make sense?


Anyways, the problem here is that some folks assumed it was rich smoke instead of oil smoke because so many newbies get on here and that got this thread all off-track.

I was just trying to state the obvious info above considering this guy knows the difference between fuel smoke and oil smoke to try to get things back on track.

But now I reckon we are going to debate how an F'n choke works? Really?

It is a friggin air intake restriction device, created to restrict air flow to a carb in order to enrichen the air fuel ratio for cold starts. Since a motor is just a dang fancy air pump with a fuel metering device and a spark plug... closing the choke is a restriction that causes higher vaccum/suction as the motor tries to draw air in.

Again this little bit could be causing the motor to pull in oil from a minor condition or causing the trace of oil to burn dirtier due to reduced air in the mix.

Geez.

[laxman1306]

i believe it is pulling through the breather thats really the only way i can see it pulling oil from and the oil consumtion is miner, we are talking maybe a couple ounces between oil changes which would be from having the choke on to let it warm up...and the oil burning is only with the choke all the way on ....if i turn it all the way on then back it off a little it will not burn any oil

[JOHNDOE83]

You deffinetly have a bad valve guide or seal, possibly a ring issue.

It can happen to anyone during a rebuild, dont feel bad about it, one lil nick while installing and you have a leak.

It is NOT normal for oil, wet or burnt to be in the exhaust ever.

Smoke and burnt oil in the exhaust happens when oil leaks into the piston chamber where its not supposed to be, the only way it can get there is through a crack in the head or a bad valve guide and seal or ring.

If wet oil is coming out, its because your leaking a decent amount of oil when cranking the motor over when its not started, this pushs wet oil from the piston chamber to the exhaust. Then when the motor starts, you get smoke and oil spray.

When the chokes off you dont notice it because the smoke is white and very faint from being burnt and mixed with gas.

It could be a bad valve or mis installed ring, my money goes to the valve.

The only way to find out is to pull it apart and look, bad valves arent noticeable to the naked eye unless they are really bad. yours arent really bad aparently but you deffinetly have something wrong.

Have you noticed oil level dropping at all?

The crankcase breather is NOT going to put oil in your exhaust.

[MtnEX]

It is easy enough to pull the breather tube and block off the hole to see.


If it were me that is what I would want the problem to be because that would be an easy fix.

I believe it is internal though. :(

[fearlessfred]

Originally posted by MtnEX
When the piston goes down it is sucking harder than it would be with the choke open.

I just tried to put it simple like, think of a vaccum cleaner like a shop vac... you are sucking with the open hose, then you shove a crevice tool on the end.

If it has a problem where it can pull oil in the combustion chamber it might have enough suction to pull it on in with the choke closed and also not have enough air to burn it near as clean, so oil smoke would be more easily visible in either situation.

Make sense?


Anyways, the problem here is that some folks assumed it was rich smoke instead of oil smoke because so many newbies get on here and that got this thread all off-track.

I was just trying to state the obvious info above considering this guy knows the difference between fuel smoke and oil smoke to try to get things back on track.

But now I reckon we are going to debate how an F'n choke works? Really?

It is a friggin air intake restriction device, created to restrict air flow to a carb in order to enrichen the air fuel ratio for cold starts. Since a motor is just a dang fancy air pump with a fuel metering device and a spark plug... closing the choke is a restriction that causes higher vaccum/suction as the motor tries to draw air in.

Again this little bit could be causing the motor to pull in oil from a minor condition or causing the trace of oil to burn dirtier due to reduced air in the mix.

Geez. yea really .you are the one who posted a bunch of nonsence about the choke greatly increacing vaccum the vaccum is the same inless you change rpms. the throttle blade is the restiction .when the choke is on the vaccum does increase between the throttle blade and the choke blade , but overall manifold vaccum remains the same at a given rpm.there is ho debate on how a choke works,only a debate on your statement.now john doe has it correct.if the motor is truly sucking oil than there is definitly a mechanical problem

[bcleveland]

Hey bud I think what is going on with you is cylinder wash. You are probably a little rich on your jetting to begin with and when the choke is on its dumping a crazy amount of fuel. So much in fact its washing the oil off the cylinders and burning it. Which makes it smoke and will blow out a greasey residue just like a 2 stroke. I dont think its a ring bad rings are bad all the time not just when the choke is on. And guides will get worse as they heat up and will smoke like crazy with you let off and idle down.

[MtnEX]

Originally posted by fearlessfred
yea really .you are the one who posted a bunch of nonsence about the choke greatly increacing vaccum the vaccum is the same inless you change rpms. the throttle blade is the restiction .when the choke is on the vaccum does increase between the throttle blade and the choke blade , but overall manifold vaccum remains the same at a given rpm.there is ho debate on how a choke works,only a debate on your statement.now john doe has it correct.if the motor is truly sucking oil than there is definitly a mechanical problem

Yeah yeah yeah.... :rolleyes:

I refuse to "debate" with someone who doesn't understand that the 4 stroke engine itself is a vaccum pump.

When the piston goes down on the intake stroke, vaccum is created every-flippin-where above the piston out to the filter media, PERIOD. Non-debatable.

The point I was trying to make that you can't seem to grasp... well I will give you a test you can try on your mama's vacuum cleaner.

Turn it on and loosen the hose. Then see how much suction you feel on that loose connection. Then take your other hand and totally clog the end of the vacuum hose. Now make a mental note of how much more vacuum you have through that loose connection than you had before. Repeat if you need to, test it if you need to.

Likewise if you have an engine issue that will allow oil into the combustion chamber, the piston is going to draw more into the cylinder with an intake restriction such as a closed choke... and it is also going to have less air supply to help burn this.


I mean frick... why do you think they vent the crank case to a flippin hose and route that over to near the filter end of the intake tube to begin with??? Why not just have an internal port to vent that right up out of the crankcase and over to the top side of the piston?

Oh yeah, I am real sure they do it that way cause it is fun and cool and adds almost as much power as well greased muffler bearings.

[fearlessfred]

Originally posted by MtnEX
Yeah yeah yeah.... :rolleyes:

I refuse to "debate" with someone who doesn't understand that the 4 stroke engine itself is a vaccum pump.

When the piston goes down on the intake stroke, vaccum is created every-flippin-where above the piston out to the filter media, PERIOD. Non-debatable.

The point I was trying to make that you can't seem to grasp... well I will give you a test you can try on your mama's vacuum cleaner.

Turn it on and loosen the hose. Then see how much suction you feel on that loose connection. Then take your other hand and totally clog the end of the vacuum hose. Now make a mental note of how much more vacuum you have through that loose connection than you had before. Repeat if you need to, test it if you need to.

Likewise if you have an engine issue that will allow oil into the combustion chamber, the piston is going to draw more into the cylinder with an intake restriction such as a closed choke... and it is also going to have less air supply to help burn this.


I mean frick... why do you think they vent the crank case to a flippin hose and route that over to near the filter end of the intake tube to begin with??? Why not just have an internal port to vent that right up out of the crankcase and over to the top side of the piston?

Oh yeah, I am real sure they do it that way cause it is fun and cool and adds almost as much power as well greased muffler bearings. the throttle blade is the restriction,until you open the the throttle it remains the restriction.if you open the throttle with the choke on ,then the choke becomes the restriction. at no time does the vaccum greatly increase and any vaccum increase down stream of the choke will not even register on a guauge .the vaccum will increase down stream once the choke is off and the throttle is open.the greatest vaccum is seen when the rpms are the greatest for slightest amount of throttle opening.the vaccum down steam of the throttle blade will never be greater than the vaccum on the engine side of the throttle blade.there is no arguement that the engine is a vaccum pump or how it works.as far as the crankcase breather goes,it is placed were it is for pollution control and positive ventilation. a motor in good mechanical condition will not see any measurable oil lose thru the crankcase vent. if the rings are not sealing and there is excessive blowby,the oil loss has nothing to do with the choke being on.i have the feeling you have never used a vaccum guage in your life

[MtnEX]

Originally posted by fearlessfred
the throttle blade is the restriction,until you open the the throttle it remains the restriction.if you open the throttle with the choke on ,then the choke becomes the restriction. at no time does the vaccum greatly increase and any vaccum increase down stream of the choke will not even register on a guauge .the vaccum will increase down stream once the choke is off and the throttle is open.the greatest vaccum is seen when the rpms are the greatest for slightest amount of throttle opening.the vaccum down steam of the throttle blade will never be greater than the vaccum on the engine side of the throttle blade.there is no arguement that the engine is a vaccum pump or how it works.as far as the crankcase breather goes,it is placed were it is for pollution control and positive ventilation. a motor in good mechanical condition will not see any measurable oil lose thru the crankcase vent. if the rings are not sealing and there is excessive blowby,the oil loss has nothing to do with the choke being on.i have the feeling you have never used a vaccum guage in your life

WTF?

Who is talking about downstream besides you dude? The oil ain't coming from downstream. The only way it could is through the block breather and what you are saying is why they pipe it out there instead of just routing it internally up through the motor.

Guys like me think the EPA can screw off and don't route hot gasses into their intake air path. (Totally utterly retarded if you think about it).

Dude I modify and race a quad that is fuel injected and has a downstream vacuum sensor and I build custom intakes and remap ECU's... so yeah, um... I got vacuum gauges.... and furthermore I have a special setup just for powersport engines. Inlet air pressure (vacuum) is one of the parameters used in the ECU's logics.


Anyways, a restriction is a restriction and the engine is trying to intake and does not care where the volume comes from or what it is. It is creating vacuum and drawing in. If you limit the amount of air it can draw in with a choke, it's not there as part of the mix. And if air is restricted it is drawing harder against everything else.

Oil is coming from somewhere internal and more of it is being drawn in due to the choke being closed and less air is present to assist with the burn.

A leakdown test would be a good idea to determine where it might be coming from.

[powerbomb400]

The crankcase vent hose is to vent pressure buildup in the crankcase from the crank turning. The choke shuts off airflow to give more gas than air. The vacuum inside the intake will increase as the piston strokes faster on the intake stroke. I'd guess its either coming from a valve guide,condensation off the header mixed with raw gas. I know that I don't leave my choke on full. Just enough to crank if it is super cold. Then I'll go 1/2 choke to warm alittle then turn it off altogether.