hi all i have a xv 1600 on a o2 plate that on a ride out started to missfire. only on the front cylinder. i have checked everything that is pointed out in the manual eg pick up resistence.kill switch.wireing loom.compretion tested.valve clearinces the lot.i have changed the plugs coils even the cdi unit. but still she missfires on the front and only the front cylinder. can anyone please help as im at a dead end. many thanks you guys. carl.