Spitting oil out Exhaust (4 stroke)

[CAL]

A buddy of mine has a '95 TW200 that is spitting oil out the exhaust. I didn't believe him, so he brought it over and sure enough it is pumping oil out the exhaust. Enough to coat the rear wheel from seeping and it sprays all over the rear of the bike.

My first thought was a broken or missing ring allowing blow by, but it has great compression.

I haven't tore into it yet, but I'm not sure what to look for besides a severely cracked head?

Any ideas? :think:

 

[sx_dude]

oil cum out pipe

well i few weeks ago mine chucks oil out of pipe only wen it's cold but mine needs to fuel mixture sorting out because it's to rich but it wont be that if it's chunking loads out it will prob be a oil seal inside your engine and it's getting in ya combustion chamber and chuking it out of pipe so it calls for the engine to put took out and split in half to cheack for ya seals im not sure about 4 strokes tho really coz they have oil in sump not like 2 strokes were it's lubrcanted by the oil and fuel mix it cud be a piston ring like u said were oil cuming out of sump and past the piston ring so id check that first ok dude

 

[sx_dude]

oil cum out pipe

but mines 2 stroke rm125 so it's gonna be a bit diff but it will proberly be 1 of them to i stated above

 

[matt-itude]

sounds kind of weired because on a four stroke if you get oil in the combustion chamber there should be blue smoke too especially if there is enough to blow out the pipe. look for carbon or oil on the plug. it sounds unlikely.

 

[Bodge]

Sx dude. Have you ever heard of using periods? Your post was hard to read. As to the 4 stroke, could it just be old carbon that heated up or something? Is it possibly for the exaust valve guide seal to have given in? Wouldnt this let oil into the head pipe?

 

[CAL]

Sx dude. Have you ever heard of using periods? Your post was hard to read. As to the 4 stroke, could it just be old carbon that heated up or something? Is it possibly for the exaust valve guide seal to have given in? Wouldnt this let oil into the head pipe?

I thought it was carbon and possibly unburned bad gas...until he brought it to my house. It is most definately oil being pumped out the exhaust. The rear wheel is covered in oil.

A valve stem seal (like you said) is my only rational guess. The amount of oil coming through makes me think the seal is completely gone.

 

[Rich Rohrich]

Besides the possibility of a bad valve seal a ring problem is still possible. If the second compression ring fails then you'll have an engine with great compression that pumps oil like mad. The second compression ring is really nothing but an oil scraper. Looks like it needs to come apart either way.

 

[reelrazor]

I thought it was carbon and possibly unburned bad gas...until he brought it to my house. It is most definately oil being pumped out the exhaust. The rear wheel is covered in oil.

A valve stem seal (like you said) is my only rational guess. The amount of oil coming through makes me think the seal is completely gone.

Does it have blue smoke coming out the tailpipe while running, especially at startup? If it doesn't you need to be looking elsewhere for your oil leak.

Many engines get by without an exhaust valve guide seal at all and don't have this problem. The intake side is exposed to intake vacuum and therefore is more important to have a seal as it will pull oil into the intake port. The exhaust side seal is more for keeping exhaust from getting up the valve guide than keeping oil from getting into the exhaust port/pipe.

You say it has oil on the rear wheel. Could it be coming from somewhere else? Like a bad crankcase breather vent hose? Or a crankcase seal, like the countershaft or shift shaft seal?