Big bang starting the bike when cold.

so when the bike is cold and i start it, it usually idles at 2000rpm before the auto choke thing lowers the idle to around 1200 which it stays at, but for the past couple of mornings i start the bike and it initially idles at 1300rpm and then there is a bang which shakes the tank and the idle goes up to 2000 and the bike carrys on as normal? any ideas what this could be? its a 2003 pointy with a recent service, could it be spark plugs?

Just unburnt fuel, my Curvy does it sometimes, it is nothing to worry about as long as it only does it the once on start-up.

it does it most times i start the bike unless the bike is already hot? so just unburnt fuel? mot is tomorrow so may ask them just to look/confirm it cheers

also the bang seems to be from the throttle body area and not the exhaust

Yeah, it don't half make you jump when you have the airbox off balancing the carbs when it does it (I speak form experience!)

cool nice one, was starting to duck when starting the bike just incase it blew up on me or something

From your photo you have a pointy? So carb balancing issues are non existant as such.

I have got mine to misfire which sounds like more of a cough than a bang, but the sound comes from the airbox area. Dodgy spark plugs could cause this. Are they new / gapped properly?

I've had the bike 2 years and not changed the plugs, should I?

Im not 100% sure of the proper service interval, but I have changed mine every 8k miles or 2 years since I got my bike. You could always pull them out and see what state they are in! Theres a good amount of charts online you can compare them to to see if they are healthy!

Gonna pull them out tonight to have a check cheers