I have a 99 CBR 600 F4. It drives fine when it is cool but after driving it for a while it starts to heat up mostly in stop and go traffic. If I am sitting at the light the gauge reads half way then when I take off it starts hitting the top and it gets to Hot until I drive a little and cools back down. Now to compound the problem when it heats up the fan kicks on and causes the engine to stumble coming out of first gear.

I changed the regulator rectifier to the new oem honda one with the metal fins and still does the same thing.

 

The fan should come on around 220F and cool the bike down. I have never heard of the fan causing a bike to come out of gear or ever thinking that its possible. is your battery dead causing a misfire to the cylinder because your fan is drawing power and your bike cannot recharge it?

 

No not coming out of gear,lol. I mean as I am driving it from a full stop it stumbles like its about to cut out and I have to give it gas to keep it going. I have set the idle to about 1,500 rpm to keep it from doing it but its not really a solution. The fan comes on just fine it just when it does the bike starts hestitating

 

are the sparks old? I think that the battery may be so weak or your sparks so old that when your fan does come on it draws so much that the sparks dont get enough and the bike begins to misfire. Its the only logical thing that connects the fan coming on to the bike stumbling

 

Dam you might be right. I bought the bike 6 months ago changed the oil but not the spark plugs. But what about the overheating, should I do a coolant change?

 

Yeah i would do a coolant flush. Drain the old coolant, fill with distilled water, run for a few minutes and drain. Then fill it with Honda Pro Coolant, or whatever other coolant you use.

 

Ok I will go ahead and do those two maintenance and let you know if it worked. Thanks for the help

 

you're welcome

 

UPDATE!!! I changed the cooling fan and did a complete coolant flush per the Honda Shop manual. And I am happy to say the bike is running at temperature and not overheating at ALL! Also I am going to be installing NGK iridium spark plugs this weekend? any experience with these are they work the extra money?

 

They work great and im glad to hear the CBR's running good