Hi all just bought my first 600cc bike a stunning 2000 f4, when out for a while on my first ride I noticed that it bogged down and stalled at traffic lights but thought it was probably rider error for it to happen a few more times. Upon further investigation I have noticed a trend which is that when started from cold the bike fires up straight away no issue at all and really crisp throttle response, when warmed up at first all is good. After idling/revving a bit for a while longer the bike bogs down and cuts out. Now what usually happens is that the bike reaches operating temp, the fan kicks in and all is good then the fan goes off and when it comes on again the problems then seem to start, which is the bike starts spluttering the lights on the dash start flickering then it bogs down and dies, if I try starting it straight back up the bike misfires with a big bang then starts but again cuts out and if you try revving it as its dying it just bogs and dies sometimes with the fan on and sometimes without. If I leave it 2 minutes and start it again it seems to start no issues until again the operating temp is reached. Now I did think a charging issue but I have checked the stator and all looks perfect with that completely within specs, reg rec is also testing ok and appears to be working correctly charging correctly at 5000 rpm but when the engine does die I have noticed the meter dipping to just over 12v when it happens, (don't know if the engine dying is causing the drop in voltage or the voltage drop is causing the engine to die) my next thought was possibly carb ratio maybe needs adjustment or do I try a new reg rec and see if that cures it but wanted to ask you guys opinion first before throwing more money at it. Also I have fitted a brand new battery already to no avail. Thanks in advance

 

I can't say for sure, but there's a chance it's the coils. I'm currently having very similar issues with my f4 and after some trial and error I found out that a coil was causing it. But before you try replacing any parts, I would check every ground on the bike. I personally know of three. One on the reg/rec, one one the wiring harness between the battery and carbs on the left side of the bike, and one on the starter. And check your coolant, I had a coolant leak and because of that I blew up the motor that was in it. Hopefully it's just a ground and you don't have to go through the pain I did trying to diagnose it. Good luck.

 

thanks for the reply, I've checked the coolant level and all is good. When you say to check to grounds do you just mean clean them up and make sure they are getting good contact? Also does anyone know what the best way to test the coils would be? Thanks

 

Yea just check them for corrosion. Even if there clean I would still take sandpaper to both surface's of the ground. I'm not sure how to test coils with a multimeter. The way I did it was swapping coils around and covering each carb till I found the problem cylinder. Not sure if that will work in this situation though. You should find a way to test them online somewhere.