QuestionI'm still looking for a good deal on a used Virago XV700. This one has 10K mi. Tends to backfire during upshifting, once or twice during a 5 minute city commute. It sat for a few years, then had the carbs cleaned and syncronized last spring before the present owner bought it. Recent oil change, filter and new sparkplugs. What are the possible causes of the backfiring?
Many thanks,
Berry
AnswerBerry,
backfiring has many causes, alot of bikes
new and old have the occasional backfire.
Newer bikes are running very lean fuel mixtures
which tend to contribute to the problem.
-here are some of the possible causes
of backfiring:
I believe the most common reason for backfiring
is changing to aftermarket exhaust pipes.
Most of these pipes have less backpressure
and different design than original pipes.
This allows fuel to get so lean it won't burn easily and so passes into
the exhaust pipe where it starts burning or backfiring.
Also,
-intake air leaks
-exhaust system leaks, bad gaskets or clamps.
-spark plug heat range too hot
-poor engine cooling
-lean fuel mixture
-bad air cut-off valve on carb
-evaporative control valves (emissions)
-idle set too low.
-excessive carbon buildup
-carb heater stuck on.
-defective ignition components.
It may be very hard to totally eliminate
all minor backfiring. It tends to be the
nature of the (motorcycle) beast
to have the occasional "pop"
