1997 Honda XRV750 start up problem

[Edwh]

The problem is when i start my bike from cold it wont start on both cylinders. one cylinder starts with the other cylinder starting with a backfire about 15-30 seconds after that. i've put new plugs in and no change. heads have twin plugs too if thats any help, and twin carbs. any thoughts??

[Motu]

Sounds like one carb is low on fuel on start up....draining while standing.I think the XRV750 has an electric fuel pump,powered by one CDI unit....so it doesnt work until the engine is running.That's why one cyl comes in late,it's not running until the bowl is full.It could be loosing fuel externally,or internally into the cyl.Put your hand on each pipe to see which one is not picking up.Check battery voltage under cranking - the pump won't work under say 10 volts,so when you let the button go,then it will fill that carb.Swap CDI units at the plugs and see if the problem cyl changes.