ok i have a right cylinder back fire at low rpm and only idles on one cylinder.when i pull the choke out it runs on both cylinders and the back fire goes away.so i took it apart and found a pin hole in the cross over tube betweenthe carbs.so i covered the hole up and started it and it still seemed to have a back fire.i checked both carb boots and there perfect.all the gaskets are good,this was the only thing i could find.the carbs have 250 mains and 25 piolet.the bike is all stock except for the exhaust.full fmf gnarly pipe.its also around 50 deg.at sea level.any help would be great.thanks for ur time