How do you tell if it is working I have watch the radiator while running and it does not look like the water is circulating i watched it till it was hot enough for the thermostat to open. Also is there a kit to rebuild it on the market

 

Run it while looking down the rad cap hole with rad cap off. You will see if the antifreeze is circulating easy enough.

Also if the top and bottom rad hose are both firm and warm after warm up, that tells you its circulating.

That's how I found out I had a air lock in the system once. The bottom rad hose was cool and soft while only the top rad hose was hot and hard ,when both should be hot and hard.

 

Is it getting hot? Hot light on, fan not kicking on? Leaking anywhere? Rare occasions if it doesn't appear to be circulating through the radiator and the hot light comes on,the impeller itself could have melted from heat because of air(cavitation) or it can be loose on the shaft and not turning. Dirt Cheap Yamaha & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

what did you do for the cavitation problem

 

This only happens if there is any trapped air in the water pump cavity. The air/coolant can get soo hot the impeller can melt.Same thing I found on water craft impellers that had air seep between the pump housing gaskets. Aluminum impellers would be melted down. Even stainless steel impellers would have holes in them from the super hot air. You have to replace the impeller,new gasket and keep the radiator cap off until any air is purged. Plus I've seen the impeller nuts just back off(probably weren't tightened enough) and impellers wouldn't turn with the shaft. Usually they'd get super hot if this happens. If the hot light isn't coming on,fan kicks on and off ok,no apparent leaks,then I wouldn't worry about it. Most thermostats aren't the problem if it's never overheated. Only replaced a couple that I can remember. One the rubber o ring around the thermostat was melted,the other one the small pin in the thermostat was coked,not allowing it to open fully.