QuestionHi Wayne,
this is my first ever motorcycle and after I changed the oil (I put in 10-40 motorcycle oil) and put in half a can of seafoam cleaner in the gas and ran it through. The bike now backfires and is starting to blow smoke. I have checked the shop manual and I did not find anything on backfiring. There is plenty on the smoke but would love to get you input on both.
Thank you
Brian
Answer
Hi Brian,
Always check compression before tuning an engine
or have a cylinder leak down test done
to ensure the rings and valves are sealing.
Backfires can be caused by a few things.
Main cause is a lean fuel mixture.
If the carbs were not soaked in some
good carb cleaner the passageways could
still be plugged.
Brass carb idle and main jets should be physically
cleaned with a small smooth wire or such.
Another cause for backfiring is any exhaust
leaks such as the gaskets near the head.
Another cause for lean fuel mixtures are
air leaks around the carb mounting rubber
or gaskets. Any air/vacuum leak can
cause a lean backfire.
Lean backfiring may also be joined
by overheating and smoke.
Intake air leaks can sometimes be checked by spraying
some carb cleaner or starting fluid around
the intake area and see if the idle speeds up
indicating an air leak.
Blue smoke could be bad fuel, overheating,
worn rings or valve seals.
A plugged engine breather or plugged
air filter.
Black smoke is too much fuel or not enough
air going into your engine.
Could be leaking carbs or bad air filter.
I would suggest checking your spark plug colors
for clues and adjusting things depending on
the plug colors.
Black plugs are worn engine or too much fuel, not enough
air.
White or light colored plugs are dangerous
and mean oveheating, not enough fuel,
bad air filter. Check your fuel valve
and carbs.
If the plugs stay a nice light brown or tan
color after a fast run then things are okay.
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm
Sometimes it takes awhile for the fresh
fuel to circulated and some seafoam
might cause a little smoke.
So,
Check plug color.
Check your charging system for 14 volts at fast idle.
Check fuel supply and carb jets, passageways.
Good luck!
Wayne S.
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