how do you test the coolant temp sensor in 02?

I can tell you that mine was quite consistent whem mine went out, would rev to ~5000 and hold - no bogging/backfiring.

To test: You can get a bypass kit here from SLP. I carry one now just in case of another failure.

Testing coolant temp sensor is easy. It should read a certain amount of ohms at a certain temp give or take some. I threw my manual away when I got rid of the 800 rmk I had so I wouldn't be able to give you exact numbers.

You can also take it out, put it in a pan of boiling water and then take the reading as well. They give you a number for room temp (68 F and a reading for 212 F)

They were known to be junk. Most of us when we had that sled always carried a spare or two in our packs. Simply unplug the bad one and plug in the new one. You wouldn't have temp protection but at least you would have power until you got back to the lodge where you could change it out with proper tools.

I know this sounds really stupid and basic but double check the plugs my brother had a similar issue and the plug had no gap after being put in a spring loaded plug holder. I'm sure you've changed them but it's just a thought.