Topic: Need advice!! Watch video

[Jaxbchcb]

My bike is idling really high and smoke is coming out of the front of the motor and #3 exhaust! It's a 1972 cb750 sohc, valves have been adjusted, timing has been set, new plugs. Did have way too much oil in it but drained it and refilled so I don't know if it's just burning access oil or something more serious!?

[flybox1]

you have an exhaust leak at the head.
did you recently remove and replace the exhaust?
new copper crush washers are needed every time.

Does the exhaust out of #3 evaporate like water vapor, or does it hang around?  might just be condensation if you havent run the bike up to op temps recently

[Jaxbchcb]

you have an exhaust leak at the head.
did you recently remove and replace the exhaust?
new copper crush washers are needed every time.

Does the exhaust out of #3 evaporate like water vapor, or does it hang around?  might just be condensation if you havent run the bike up to op temps recently

I just put brand new crush washers on all four exhausts. The smoke goes away pretty quick but wouldn't call it a mist because it smells like burnt oil

[flybox1]

looks like you need to 'crush' your crush washers a little more to get a proper seal.

condensation will smell like that, too.  if its white smoke, no worries.  if its blue, you're burning oil.

[Jaxbchcb]

looks like you need to 'crush' your crush washers a little more to get a proper seal.

condensation will smell like that, too.  if its white smoke, no worries.  if its blue, you're burning oil.

Just tightened the exhaust bolts as tight as they can go and still the same thing? The smoke looks like it's coming from the center of the engine

[Jaxbchcb]

Just looked at it with a flash light and there's definitely oil coming out of the #3 header

[Jaxbchcb]

Bump

[mystic_1]

Well, that's one of the classic leak positions for "leaking head pucks" type of oil leak.  Are you sure the oil is coming out of the header, or is it coming from the fins next to the header?

If it's a puck leak, that requires removal of the valve cover and valvetrain including the camshaft and cam towers, but you don't have to crack the head off the engine.  In a stock unmodified frame, engine removal is required.

Might want to try to peek between those fins with the engine running, to see if you can spot the source.  You can also clean the area really well with degreaser, then rinse with water and allow to try well, then spray the area down with spray foot powder or talc.  Then run the bike for a little while and the source of the leak should be very apparent in the talc dust.

mystic_1

[Jaxbchcb]

Well, that's one of the classic leak positions for "leaking head pucks" type of oil leak.  Are you sure the oil is coming out of the header, or is it coming from the fins next to the header?

If it's a puck leak, that requires removal of the valve cover and valvetrain including the camshaft and cam towers, but you don't have to crack the head off the engine.  In a stock unmodified frame, engine removal is required.

Might want to try to peek between those fins with the engine running, to see if you can spot the source.  You can also clean the area really well with degreaser, then rinse with water and allow to try well, then spray the area down with spray foot powder or talc.  Then run the bike for a little while and the source of the leak should be very apparent in the talc dust.

mystic_1

I think you might be right because I can feel hot air actually blowing from the fins!?

[mystic_1]

Well you definitely have an exhaust leak where the exhaust pipes meet the head, that's fairly clear from the video.

I'm saying you might have both and exhaust leak, and an oil leak.


Those are aftermarket drag pipes with the flanges welded right to the pipes, yes?  If so, there may not be enough "spout length" so to speak "above" the flange, between the flange and the head.  If not, then the end of the pipe won't crush down on the gasket to make a seal.  I'd pull off one of the pipes to see if the gasket got compressed at all or enough.

mystic_1

[Jaxbchcb]

Well you definitely have an exhaust leak where the exhaust pipes meet the head, that's fairly clear from the video.

I'm saying you might have both and exhaust leak, and an oil leak.


Those are aftermarket drag pipes with the flanges welded right to the pipes, yes?  If so, there may not be enough "spout length" so to speak "above" the flange, between the flange and the head.  If not, then the end of the pipe won't crush down on the gasket to make a seal.  I'd pull off one of the pipes to see if the gasket got compressed at all or enough.

mystic_1

Yeah they are aftermarket drags that were welded to the flange. I'll pull one and see. Would that cause an oil leak?

[Jaxbchcb]

Pulled the #3 pipe and this is what I got! The crush washer definitely got crushed. It looks like there is oil coming from the exhaust port though..

[HondaMan]

It looks as if it has been leaking for a long time! That's a lot of grease buildup.

I suspect you're gonna have to go inside...it's likely to be valve guide issues, at the least.

[Jaxbchcb]

It looks as if it has been leaking for a long time! That's a lot of grease buildup.

I suspect you're gonna have to go inside...it's likely to be valve guide issues, at the least.

Yeah I was afraid of that.... I got this bike not running on a trade for a gun I bought for $500 did all the basics to it finally got it running decent then this happened...... I just wanna ride her!!

[mystic_1]

I'm seeing a mark on the metal behind the exhaust gasket, at about the 4 o'clock position.  That's where I also saw the worst exhaust leak in your video.  What's up with that?