Well here we go I have a Raptor with a 686 kit 12.5 to 1, ported head,big carbs, exhaust, cam and all the usaul other stuff. Ever since I had the 686 put my Raptor will over heat. I have it getting worked on now and it has the guy stumped so he told my to try to see if anyone else could help us out.

The fan works, the water pump is pumping, we have just put in a new thermostat and thermostat housing, but we are still having it overheat. The problem is it doesn't overheat and flow out of the radiator overflow, it overflows out of the coolant bootle overflow. It also has a new heaD GASKET INSTALLED so its not that but it is building pressure somewhere and we have not got a clue to what could be going on.

Any help would be greatly appreciated

 

How is the jetting? Is it too lean? Is it over heating after a good romp or just at an idle?

 

redblue- what head gasket did you use?? I say your headgasket is bad. Do the overflow fill up faster under hard acceleration?? What gets are you running?? What is your piston to bore clearence?? Did you gap your rings??

 

Not common but the head could be cracked. you say its ported, how much so?

Try a coolant system pressure test ( a little hand pump you put on the radiator and pump up to pressure and see if it holds)

other than that there could be a blockage, like someone left a rag or paper towel in the coolant passages in the head or hoses to block them off since it has been worked on recently.

How quickly does it overheat? is the fan running at that time? The more info the better.

 

sounds like someone may have ruined your head while porting...

 

the jetting is 138 in both carbs this is where it seems to run the best but my carbs are still a little out of adjustment, and the bottle level will increase at idle but it will not overflow till full throttle is applied, I use a big bore head gasket the last one was from sparks this one is from cometic, I don't remember the piston bore clearance but the guy that installed it knew what he was doing, and the rings aren't gapped that I'm aware of, and trinity ported the head. and it is getting worked on as we speak.

 

I still say your headgasket is the culprit. Trinity does not remove enough material to get in a water jacket. those jets seem a little low. Is that the jets that trintiy put in your fcr's?? What needles?? Install a hp gasket and go ride. Call craycraft at 817 441 5893 and motor on

 

When I got my first headgasket from Sparks it was a factory OEM Yamaha headgasket. I didn't use it I got a HP from 14mins. I don't know if Sparks sells HP but thats what I run and have had NO problems what so ever even with my 12.1 piston.

 

Who installed the head gasket? Didn't I hear something about puting it on upside down or backwards and blocking a water port or something?????