White smoke coming out of left cylinder. Both cylinders running

edmond

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So after oil change and rebuilt carbs, my 78 xs650 starts and runs. I'm having an issue of white smoke coming out of the left cylinder where the engine meets the bolted in exhaust. It's a moderate amount of smoke that starts coming out after a few seconds of run, when the engine and exhaust gets hot.

Any ideas what I should look out for? Both cylinders are running, I'm getting good compression and the carbs are doing OK having rebuilt them.
 
How long since last ran? How much oil did ya put in it?
 
Last ran... 2007. I just got the bike, it's first extended run was a few days ago and I've been running it here and there while I fix things. Probably about 2.5 qts, dip stick shows right in the middle with the bike centered.
 
Did it not smoke on extended run? Was oil change after run? Oil weight used?
 
It smokes steadily. Doesn't get worse or better until shut off. Oil change was before run. 15w-40.
 
You could check compression, it may provide a clue. Smoking, as you describe could an be issue with cylinder/piston-rings or potentially a valve seal problem. White/blueish smoke generally indicates oil burning; unburnt fuel usually blackish or gray. Valve seal issue usually worse at start-up and sometimes clears when run.

Add; check crankcase breather - though that should affect both sides
 
out of the left cylinder where the engine meets the bolted in exhaust.
Yea, I wasn't reading very carefully; does it not smoke out the muffler?
 
You could check compression, it may provide a clue. Smoking, as you describe could an be issue with cylinder/piston-rings or potentially a valve seal problem. White/blueish smoke generally indicates oil burning; unburnt fuel usually blackish or gray. Valve seal issue usually worse at start-up and sometimes clears when run.

Add; check crankcase breather - though that should affect both sides
I will definitely check for compression. But then I’d have to buy the tool. Generally, how much smoke is too much smoke (not road ready levels)?
 
If the smoke isn't billowing out the exhaust (muffler) - just an exhaust leak?; probably not a big concern. Compression gauges pretty inexpensive though.

https://www.autozone.com/test-scan-and-specialty-tools/compression-tester
Wow, good catch there! Logically it should just be an exhaust leak as there isn't a huge cloud of white smoke out the actual muffler. I took out the connection and didn't see any metal gasket/ring in there. I'll try tightening it up good to see if that helps.
 
It was actually DogBunny's catch, but thanx.

The original exhaust gaskets are soft aluminum and, once ran (old) can appear to be part of ex. port. Without good gasket, it will not seal. Danger Will R. - ex. studs can be damaged!

Sorry - "Will Robinson" = '60's TV reference
 
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Loosen muffler brackets, header frame brackets, down under engine.
It takes a bit of care to snug both collar nuts evenly.
Do NOT go Ape on the nuts.
As suggested best to remove the pipe and check that each side has ONE crush seal in there. the collar should end up nearly, but not quite, touching the head, evenly all around. If the collar is stock this is what about you want to see;
head detail exhaust collar.jpg

Note several items can leak oil and let it drip on the exhaust in this area, the valve cover is VERY popular for this. Cam seals too. Not to mention oil from top end lubrication while doing a wake up.
 
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80024B44-F3C1-4207-859B-1CA09C8D32E0.jpeg
so… I took off my exhaust pipes and this is what I found. This ring is welded on I think. Is this the crushing? If it’s not, there’s nothing else so I guess I’ll have to buy some.

I also checked both of my spark plugs to see if they were running differently. On the right side, the plug was more shiny and almost went looking, whereas the left side was dry but a similar shade of black. Any idea what this may signify?
81C2A49A-C678-45C4-AE9E-4643CF76238C.jpeg
BDC76910-D8B9-42A6-83EB-780F4757EFF1.jpeg
 
The "crush" gaskets are likely still in the exhaust ports. The pics just show the original header pipes.
 
The suspect cylinder's plug being dry, while the right is wet? Perhaps the exhaust leak is messing with combustion. I call indeterminant at the moment. Perhaps cleaned plugs after exhaust is sealed and more info. will give another indication.
 
If I have trouble sealing the exhaust up, I sometimes clean up the mating surfaces real well, install a new sealing ring and smear a very light film of red high temp silicone on both sides of the sealing ring. Snug everything up and keep fingers crossed. The silicone should be used sparingly.
 
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