left side smoke

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Apr 15, 2007
Hello everyone,
I went for a ride on my 1971 commando on saturday with some friends, and after we stopped they told me that every so often I was blowing some smoke from the left side exhaust pipe.Not constantly,but enough for them to notice.Coming only from 1 side is a little odd too. Is this a valve condition? Rings? The bike has 11,300 miles on the motor and runs fairly well. What should I look for?

Thanks ,
Learn to tell the difference between oil fouling and gas fouling when reading your plugs it' not easy sometimes with todays gas. Look down inside with the plug out on the top of the piston a light dusting of carbon is OK but any kind of flaking or wet looking soft stuff would indicate oil. From what I have seen most common rings never seated right because of too fine a hone or the hone was done at too much angle spinning the rings or too little not spinning at all. With mileage and good power as you claim valve guides sound more likely. BUT, before you do anything rash try new needle jets, your miles indicate the need for replacement at this time and their wear would also put out small short wisps of smoke.
Mine was blue smoke from left side on acceleration, new rings cured the problem.
mikejet said:
every so often I was blowing some smoke from the left side exhaust Mike

Did your friends notice the circumstances under which smoking arose ? If it was just on shutting off then it might well be inlet valve guides. The earlier 750 guides are a bit known for this and can also loosen in the head. A standard fix is to bore out and fit the later 850 guides.

These things usually do become noticeable first on one cylinder or other. Depending on your mileage and use, it might be worth living with until it gets worse. If there is no wetting of plugs or excessive oil consumption, then it doesn't mean that catastrophic failure is imminent :)

If you're really "laying smoke" under acceleration then you can probably suspect piston or rings and if it is a recent thing then you probably should have a look inside in case something is breaking up.
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