Hey fellow F4 riders,

I recently bought a 99 CBR f4. I have been reading up on this hot stall issue but just wanted to get some more opinions on it.

My bike seems to exhibit the classic symptoms. Bike runs great until the thermostat gets to about half way up. I think when the fan kicks in, the CBR wants to bog out and die. It stumbles and idles very roughly. After reading through some threads, some seem to just accept this as part of an F4's personality but I refuse to. Forget about the embarrassing part, it's quite unsafe to have a bike stall out on you when you are trying to make a turn, etc.

THe previous owner had already replaced the stock rectifier / regulator with the updated F4i one with the fins. I ran the battery through a few tests today with the volt meter.

1 - No load - 12.5 volts
2 - On position - 11.8 volts
3 - idle - 12.9 volts
4 - 4000 rpm - 14 volts

Thoughts?

Thanks in advance.

 

Anybody?

I let the bike warm up until the fan came on. Threw the voltmeter on there then and it read 12.5 volts at idle. Definitely gets worse (idle sputters) when I hit the brake lights and signals.

Thoughts?

 

I would venture that the circuit with the fsn is overloading. If you look at the wire diagram you'll see alot of stuff is on the same line as the fan. I would try powering the fan with a manual switch wired to the battery. Also I found a couple threads elsewhere that detailed how an 84-86 peugot(sp?) fan switch will turn the fan on at 200° instead of 225°. Haven't tried that one, I manually wired mine and installed a thumb button in the left switch housing so I can turn it on whenever.

 

I switched to a MOSFET rectifier from a cbr1000rr and my bike hasn't had that problem anymore. I also switched to a gel cell battery. I dont know if that helps but that is what i did.

 

ive done a lot of reading and research on potted electrical components like on cdi's/ ecm's ect. old wires and old electrical components (charging system, ignition system to be specific). as they age, solder points and such inside electrical components, can crack and will get bad or weak from vibration and heat. if this happens to electrical parts it can make it carry weak signals/ current especially when it starts to run in higher temps. old electrical systems do not get a long well with higher heat ranges.

when i started replacing electrical parts with brand new ones (ignition system specifically) it stopped stumbling for the most part. im sure that when i replace the cdi box, tps, and crank sensor with brand new parts it wont even be noticable.

bottom line~ old wires and components+ heat= stumble. to fix.. lol add money, (brand new, not used electrical parts) thats just my experiance.