Now that it is summer my cbr wont stay cool.

I have replaced radiator, thermo switch, thermostat, top shelf coolant, even pressure tested the system to make sure there were no leaks. It is hot in Cali right now but i have never had this problem before. Even after riding on the freeway for about 40 minutes it will climb to just below the red dash and this is with the themostat removed! I even have the aux fan hooked up to a manual switch.

Has anyone else come across this problem in the heat, it has never been a problem before the heatwave! Anyone running aftermarket fans for around town in 100 degree weather?

Last summer I replaced the engine with a 49 state (aftern 50k on the original) and am running a D&D and jet kit; however I have already been running for 5k miles plus with the temp never climbing past half. I am also using California carbs on a 49 state motor.

What if the jetting is not correct, could that overheat the engine in high temps?

 

Overly lean jetting would make it run alot hotter... worth checking

 

95 TO 96 CARBS JETTED REAL LEAN COMPARED TO THE 97 & 98 CARBS. DEPENDING ON THE YEAR MOTOR AND YEAR CARBS EVEN WITH THE JET KIT THEY COULD STILL BE TO LEAN. IN 98 & 97 they used bigger MAINS IN THE 2 CENTER CARBS TO BRING DOWN THE MIDDLE CYLINDER TEMPS. I KNOW YOU CHECKED OUT YOUR COOLING SYSTEM BUT IS THERE ANY CHANCE YOUR FAN ISN'T COMING ON? MY SON'S F-3 PICKED UP SOME ASPHALT CHUNKS AND IT JAMMED UP THE FAN.

 

If you are running down the freeway at high speeds and it still gets that hot it is not a fan issue. Everything could be working correctly.... you ever think that your gauge or sensor is bad???? P.S. your engine will not run that much hotter when it is to0 lean.... if it ran that lean you would tell because it would run like sh*t.

 

I checked the engine temp with a friends temp gun and it was up to 230+ after cooling down for a little so I know the guage isn't wrong.

I have the fan hooked up to come on when I flip a switch and it is spinning. I have found gravel in the auxilary fan before a couple times but it is clean now.

The engine was from an F3 but not sure if it was a 96 or 98.

Looks like the next step would be the jets. It does run worse when it gets hotter. I will try to remeber what jets are being used and post the sizes in case someone can compare their set up.

 

If it runs worse when it is hot then the bike is not running lean. It would be the other way around. If it was running lean it should run better when it gets hot. If you checked and replaced everything you said I would check out the propeller on the water pump. Might be damaged. Also make sure your radiator isnt packed with bugs and dirt. You should be able to see through it no problem.

 

Also before you go ripping the carbs off pull all the plugs out and see what they look like. That will tell you everything about how it is running. Lean or rich...

 

Thanks, forgot all about reading the spark plugs. That will give me the right direction. Thanks again.

 

I had the same problem with my F2. I had a manual fan switch because my sensor went bad. I had Engine Ice in it but it still kept overheating. Then I found the problem when my radiator overfill container puked out a whitish milky liquid that looked nothing like what I put in it. When I tore the engine down, I found a small crack in the water jacket around the cylinders. The only thing I can figure is that oil was slowly leaking into the coolant and finally the mixture couldn't keep from boiling and it just boiled over. Hope this isn't your case, but it certainly is possible.