It could have to do with the fuel mix or your exhaust might not have enough back pressure, i.e. too short, or not enough muffling.
A motorcycle jerk or backfire can come from the choke not shutting off completely, the fuel jets might be clogged, a gasket or seal may be broken. Valves that are out of adjustment could also be the problem.
a backfire is caused by incorrect timing or not enough back pressure in the exhaust pipe
By turning the key to the off position, you are simply grounding out the ignition
The unburned fuel is igniting inside the muffler. Let the engine run at idle for 30 seconds before turning the key off.
to much fuel is going to the engine for it to burn it all
No,they clear.
Timing is off.
probably a bad spark, itll cause your engine to misfire flooding petrol in without igniting it, when it sparks afterwards it ignites causing a bang and backfire.
Wait a few weeks until the cast is off your leg mate, trouble should go away after that.
The chain can not backfire. If it is installed off time it can cause a backfire, which could conceivably damage a starter.
it doesn't or it shouldent'
Some motorcycles have a separate switch for the headlight that works independently of the ignition. If this is not the case, then there might be a short in the wiring for the headlight.