Could well be spark plugs as suggested.but wouldnt say it happens all the time just because its a 4cyl.its the first thing i would change if they are susspect.try flicking water on to the exhaust header pipes as the engine starts to warm,or i use a multi meter with temp gauge on to see which cyl is running cool.if its only one cyl running cool then most likely to be plugs or carb feeding that cyl.if 2 cyls are down then most likely electrical.
mike
March 2009
it will be in need of a new set of plugs mate a very common problem with all 4 cyl bikes ,has it not been run for a while too?if so drain off the carbs also by undoing the small screws on the bottom of each carburettor about two turns.but definatley change the plugs for new ones just cleaning the old ones wont be a good idea.i am a bike mechanic and see this problem allthe time in fact today a put a set in a 95 1200 bandit that was missing and backfiring.after you have drained the carbs and done the screws back up put the fuel tap on pri(prime) for a minute then switch back to on before trying to start it.
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