Finally got the engine started today! WOO!!!!

Runs well apart from slight backfiring through the carbs What exactly causes this? is the ignition too retarded? Idle mixture too lean?

It only happens when you jab the throttle rather than taking the revs up slowly... does this mean its the spark timing?

Iain

usually caused by an air leak or no air filter put the choke on a little if it goes away too lean due to above

This is interesting i have the same problem.

Mine seem to be sorted. Checked silicone hose for leakage and turned idle screw 1/2 turn out and its running fine now.

It was only one cylinder that was doing it so it was either a small leak or the idle screw isnt quite ballanced with the others

Iain

when promptyly accelerating,

the spark need to come different (dunno it was earlier or retared)

also more fuel is needed during that small moment...

Sow think it has to do with the spark timeing.

when growing in revs bit by bit you donīt have de squirt and the spark problem.

Tks

If blipping the throttle produces backfires, it must be fuel. You require less advance with the throttle opne than progressive acceleration as cylinder filling will be better.
I would suggest that it will be a weak mixture. If only one cylinder I would check that all slides are lifting at the same time and by the same amount.
As was said previosuly, see what happens with a small amount of choke.