I have just purchased this used atv and am having overheating problems on my first ride with my son. I did a lot of reading through various threads and have yet to find the solution. I pressure washed the radiator, tested the fan and it functioned cleaned the relay and tested the engine temp sensor. After my machine runs at idle for over 30 minutes the fan runs as expected. However, the fan only runs for about 40 seconds and then shuts off. I believe if the fan continued to run the problem would be solved. I am thinking that the sensor in the radiator is faulty or there is air trapped in the radiator. Am I on the right track??? Some help would be appreciated.
Thanks.

 

Look up the harness coming down to the fuse block and relays located under the front panel,should be a small square circuit breaker either taped to the top of the harness or in a sealed pouch. Found em both ways. If this breaker over heats and trips or connections are corroded,the fan relay looses power and the fan short cycles and can cause over heating. You can get these at any auto store. Item #12.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse If this breaker is at fault,replace it,jack the front end up with the tires off the ground and leave the radiator cap off and let the fan cycle on and off several times. This should purge any trapped air. Top off the radiator and over flow bottle.

 

I found the relay. It was corroded as you correctly surmised. I removed it and simply bypassed it by connecting wire it was interrupting. Now the fan comes on for about a minute and the overheating has stopped. I will put a new one in today. Should the fan run for no longer than a minute at a time as long as the over heating is under control? THANK YOU AGAIN. I will now be able to get out with the boys this weekend.

 

Fan cycling on and off is controlled by the temperature sensor on the cylinder.Fan cycling can vary,the main thing is that you have full power to the fan relay. Replace the circuit breaker and have a good time on your trip.