Can anyone help,

I have a 2005 polaris sportsman 500 HO, when I Rev the engine coolant spews out of the reserve tank, it has a little hole on the cap which I imagine is there for a purpose, I have done everything I can imagine to fix the problem, jacked the bike up to get rid of air pocket, drained the rad and flushed it, put a new rad cap on. Reserve tank is just below Max level, when the bike warms up and I Rev it it comes out of the rad cap. Oil looks good, not blowing any white smoke.I pulled the thermostat out and tested it in hot water, it opened but very slow, should it open quickly ? Oil looks good, I did find some black small particles in the antifreeze from top of rad.when I take the rad cap off I can here the pressure release so I'm thinking it's not the cap..I'm at the end now, not sure what to do now.

 

Thermostat should open and close fairly slow. If in doubt replace it. I'd pressure test the cooling system and see if it holds 10psi.If it doesn't could be a small head gasket leak.If the pressure test holds then could still have a trapped air pocket.On some of the these machines I had to jack them up and squeeze the hoses to get rid of the air,especially with the remote filler caps like your model.Some took a while to get this done. Plus make sure the hoses are full and hot to show that it's circulating and the back of the radiator is clean around the fan.A lot of people had to pull the radiators to clean everything up.Plus during the bleeding the fan should be cycling on and off if it's working properly.

 

If it is a small head gasket leak is it something I can fix, what would the cost be to fix this at a dealer ? Yes fan comes on when needed. Also forgot to mention when I poured antifreeze back in the rad and filled it up, every so often it would bubble at the top of the rad, go down a bit then come back up bubble again then it would go down once the thermostat opened.

 

Still think I'd have the system pressurized first. When the fan kicks on is also when the radiator level usually goes down so that you can add coolant to top it off. If it keeps puking it up still could be trapped air,the water pump impeller could be just spinning on the shaft or damaged,or it may be a thermostat problem. Plus again the radiator hoses need to be firm and warm to show that coolant is circulating through the radiator ok. Plus again a lot of people think their radiators are clean but can be really dirty on the back causing this problem.