marino6385

OK so I just bought a 2004 Ninja250 and it keeps overheating. I replaced the radiator fan and sensor switch and today I replaced the thermostat figuring it was stuck shut. I also tried to "burp" the radiator then flushed it figuring it had an air bubble or some kind of block but no luck. One thing I have noticed though is that the fan never engages even wheel the gauge gets into the red. Any other suggestion what it might be? And why wont the fan turn on when its running so hot?

flyguyty12

Check your fuses


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Dablue1

Other than the fan not coming on and the temp gauge being in the red is there any overflowing of coolant. How fast does it overheat? Have you replaced the radiator cap. A bad cap will release pressure prematurely mimicking overheating.

he new gen and pre gens share the same cap. Stock 1.1 BAR / 16 PSI (SAE range 14-18 PSI) radiator cap # 49085-1066 can be replaced by
Stant's 10233
Prestone's RR-33
CARQUEST 33044
Gates 31336
Gates Canada 31336
NAPA 703-1406
Stant (Carded) 11233
Stant (Carded) 70233BL
Stant (Carded) 70233RD
CST 7516(@ AutoZone)

LarryJ

Sounds like a fuse. You've replace the switch and fan, so the fuse would be my next place to look. (Actually it would have been the first place I would have looked before replacing other parts or flushing the radiator).

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marino6385

Yeah I checked the fuse first and the fuse is still good. When I conect the fan wires to a power source the fan goes on so I know the fan works. The coolant doesnt overflow or anything like that. But it will over heat within 5-7 minutes of idling. Ill start the bike with the choke on and with in 7 minutes it'll be heading into the red. Ill try replacing the radiator cap too.

Thanks for your suggestions, I appreciate it.

Dablue1

What is your idle speed after the bike is warm?
You should not have the choke on for more than a minute or two.
The fan comes on when the coolant gets above about 225F. It stays running until the coolant temperature falls back below 205F. Many bikes engage the fan just below the red zone, while others have been reported engaging the fan at the mid-way point on the temperature gauge. The most important thing is that it's entirely normal for your bike's temperature gauge to run all the way up to the bottom of the red zone before the fan comes on.

marino6385

Im not exactly sure what the idle speed is. But i do know the fan isnt engaging even when the gauge is reading slightly into the red.

Dablue1

The engine should idle at 1300 (+/- 100) rpm when the engine is fully warm. If the bike is really overheating you will get some coolant being released. Just stop letting it idle so long and ride it. The temp needle will either go up or down, if it continues to go up, the fan should come on when the temp hits 225.

marino6385

Its idling around 1000rpm. Ill try to not let it idle so long and just ride the thing around and see if it helps. The previous owner put a "sticker thermostat" on the side of the engine so Im hoping he was making the same mistake. Time will tell!

marino6385

so today I tried to only leave the choke on for about a minute then started riding. It didnt overheat right away but slowly the needle worked it way into the red and the fan never kicked on. Any ideas? At this point Im thinking the replacement temperature sensor was no good.