The sensor that screws into the head. It has 2 prongs off it, one longer than the other. What goes on to those prongs? And what does this thermal switch do? I took my 1996 400sport into the garage to have the cylinder re-boared and a new piston put in and ever since it overheats. I noticed the other day that the 2 prongs are broken off, could that be the problem? It's 60 bucks plus shipping for a new one. What should I do? Can somebody PLEASE HELP!!! I have owned this bike for 14 months and have only ridden it about a half hour since. I'm starting to think it is the BIKE FROM HELL!!!!! ANY HELP WILL BE APPRECIATED!!!!

 

Hey like2ridequad,
I pulled up a breakdown of your motor and I didn't see any sensor on the head, but I see a plug on the head. The plug looks like it's goes into the water jacket. Maybe someone had a aftermarket temp sensor on it. Sorry I couldn't be much help.

 

It is a thermal switch, if you pull up the water pump diagram you will see it there. I just want to know what it does and if that can be the overheating problem. Thanks anyways.

 

Maybe the one in the head is for the temp light. I do see the sensor in the radiator for the fan. Make sure your fan does work. Sometimes they get crapped up.

 

The thermal switch in the head has 2 terminals on it , one is cut off and not to be used . I have a few in stock and to get you out of a jam I will let you have one for $52 and I will pay the shipping.

Rick Ritter

 

Rick,
What does this thermal switch do and what does it plug to? I don't seem to see any wire around it. Where does it go?

 

On a 96 400 the switch on the head controls the hot warning light. It has ONE wire going to it.

The switch on the rad. controls the fan.

 

cornbread2 is right, The plug on the head is a switch for the overheat light. When the temp. is too hot, it provides a ground for the light to come on. I believe the wire (that is missing on yours) should go to the lamp. As for the overheating, Those cooling systems are VERY difficult to purge the air out of. I had the samething happen to me on a '01 400. If you think that it is purged, then I would check, as suggested earlier, and see if the fan comes on. You can do this two ways ,obviously by riding it or by turning the key on and crossing the plug wires for the sensor on the radiator. This crossing method only checks the fan and voltage supply, the switch may not be closing when it gets up to temp. If you get the fan to come on when riding it, check the radiator, both sides should at least be warm. If one is cool, you may have plugged passages inside. Also check for a descent amount of air flow from behing the fan. If all this is well, you are down to a water pump or a bad radiator cap(venting too early spitting out the fluid, causing overheating) I think there is alot of good things here for you to try. I can not STRESS enough about he purging thing though. Good luck

 

Thanks guys, I finally decided to cough up the cash and take it to a shop. This guy does all kinds of performance mods and I have been told by about a dozen guys that he's the best in the area. I'll let you all know the outcome next week. Thanks to all WHO HAD GOOD ADVISE.