I have a 2000 F4 that runs great...most of the time. About every couple of weeks it does this thing where it'll be running fine during a ride, then all of a sudden it will start breaking up like it's running out of gas or down a cylinder and then it dies. To restart it you have to choke it even though it's already warm and has been running normally. After it starts it runs rough as though it's not firing on all cylinders. Once you rev it up pretty high it smooths right out and runs fine again. Does anyone have any ideas what may be causing this? Any input as to where to start searching would be appreciated. It has new plugs and that didn't help any. I don't know if maybe my fuel pump is going out or if I have an ignition coil going bad or what the deal is. Thanks for any advice.

 

since it does it when the bike is warm, I would lean towards an iginition issue. Perhaps a weak coil, but usually that will only cause it to break up and run rough, but still run, not completely die out. I would look into the possibility of the pusle generator going bad.

Also, next time it happens, as quickly as you can, pop open your gas cap. If you hear a woosh, then you have a plugged vent tube in the tank.

 

Thanks for the suggestions, I'll have to try the gas cap thing next time it stops raining, but I'll check the pulse generator tomorrow.

 

I replaced the pulse generator and still have the problem. I began testing the ignition system and found that when the problem occurs I still have spark at all four cylinders. The spark looks weak to me, kind of yellow instead of the blue I assume I should see. The only other thing I noticed is that cylinder number one's spark plug looked a little rich, cylinders two three and four looked normal to maybe a little lean. Any more suggestions would be appreciated.