On my 2007 Rhino 660, Just an update, as nothing in this thread solved my issue. The exact symptoms I had were as follows:
Engine starts and runs great. Until it gets hot. As soon as the engine is hot it begins backfiring, then dies, and will only restart with the choke fully engaged, and only then after sitting for a minute. I am guessing this is due to it becoming overloaded with unspent fuel. If you let it sit for about a minute, it will start back up but is unable to run for more than a few seconds at full throttle before the engine dies again. This basically puts the Rhino in limp mode.
Things I tried to do to solve the issue:
1. Rebuilt carborator
2. Changed spark plug
3. New CDI box
4. Ran a half a tank of fuel with Sea Foam additive
5. New spark plug wire / coil
6. New air filter with foam air filter oil
None of this had any effect on the symptoms at all......
The Fix -------------------
On a hunch i got out my volt meter and tested both output voltage and continuity on the leads coming out of the engine from the stator both right after firing up while it was still cool, and again when it was hot. It was faulty when hot.I am guessing this was due to thermal expansion of one or more of the coils, or a thin insulator wire caused from wear and age.
So, after ordering a new stator, and spending about 5 hours taking her apart, installing new stator, and putting everything back together, I am happy to report that i just went trail riding for over an hour and not a single backfire. I was running her pretty hard at full throttle a lot fo the time.
Replacing the stator requires draining the oil and coolant, so those were replaced with Yamaha recommended fluids, plus a new K & N oil filter. I also replaced the stator housing gasket, and the water pump gasket while i had everything open. I used locktight on all threads on reassembly of all components and a super thin coat of RTV on both sides of both gaskets.
It now runs like its brand new.