Motorcycle Repair: smokin engine, rich fuel mixture, old harleys

Question
hi, i've been takin apart an rebuilding wore old harleys since the 60's, but i've had a couple of triumphs an beezers also. my problem would be similar in any air cooled bike i think. when i got this bike it was a smoker , ran ok but it smoked so bad it lke one of those bug killers they used yrs ago. white smoke, if it was a car i'd say i'd blew a head gasket an was gettin coolant in, looks like that. but compression was very good , so i thought valve guides, an they were shot when i took top end off, some thing i've done many times. i rebored cyls. put in o/s pistons an rings. done right. started it up smoked worse. took the garage 3 min to clear out. great compression 145/135. i guess i could have covered one of the return in cyl with head gasket but both holes, nah. what ever mistake i made i made it on both cyls because white smoke is equal amount both pipes on something i've done many times before. an remember isaid it smoked bad when i got. i don't mind takin it apart again it's my hobby but unless it's something obivious i don't have any idea, except maybe restrict oil flow to top end , i've never done it but i know guys who have. hope you can help me out. thanks randy

Answer
Hi Randy,

On the liquid cooled bikes the smoke would likely
be coolant burning but on air cooled bikes
it is more likely a fuel mixture problem
unless the pipes are burning out condensation
or even the muffler lining.

Whenever you are trying to figure out an
engines problem go to your spark plug colors.
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
The plugs will tell you what is happening
inside the combustion chambers.

If the plugs are oily you have oil control
problems. If they are whitish then it is
overheating. Black plugs might be an excessively
rich fuel mixture etc.

If your engine is running lean it might
dump unburnt fuel into the exhaust pipes.
Lean mixtures have trouble burning fully.

The unburnt fuel can ignite and cause a whitish
smoke.

I would check the plugs after a quick run and
stop the engine quickly.
They may give you some clues.

Almost all oil control problems will
develop bluish smoke.
If your exhaust has been sitting awhile it
could be water vapour burning off. This can take awhile.

Keep the air filter clean and watch your
plug color. Adjust your fuel mixture
to get a light tan color.
It might take awhile for the rings
to seat also.

Make sure your plugs are the correct heat range
as overheating can also cause white smoke.
Get the timing spot on too and check the
auto advance unit is okay.


Good luck!
Wayne S.
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