As many of you proably khow I have the sparks 690 kit (minus his port work) with the 12.5:1 piston. I am running 155/160 dynojets. My quad overheats all the time. I have a switch hooked directly to the fan, so it is always on. It keeps spitting all of the coolant out of the overflow. I am running a 50-50 mix of water and antifreeze. should I switch to engine ice, or pro cool? Please help me out here. I love the power, but this overheating has got to stop. also check out my other topic on my starter problems.

 

shoolz- Are you sure the head gasket is o-kay. The shop that put my trinity parts back together muff the headgasket. You have the same symtoms that i did. Anyway a new headgasket was installed and zoom,zoom i am gone. I wired my fan directly, also. What pilots are you running? I could never get mine right with the dyno-jets.

 

I never checked my head gasket. I am running stock pilots. What pilots, mains, and needles are you runnung?

 

14mins is on point with the head gasket issue. If you are noticing bubbles as soon as the motor starts (especially under load), you could have a head gasket issue.

This could also relate to your starter problem!! If coolant is filling your combustion chamber (it only takes a few cc's, your starter could be trying to turn over some major compression.

On almost all Raptors, I have found that the thermal fan switch does not work. This is not the thermal switch at the bottom of the radiator (that is the temp light switch) --- it is the one on the top of the radiator. I simply add a toggle switch in a good location so that I can click it on if I am moving slow or just following a race. I never have a problem.

 

14min
how did they screw up your head gasket? it's not like you could put it in upside down, was it just off a bit or was the head not torqued right?
I know the 2 head bolts that fit in from the bottom are a pain to torque, first time i tore my motor down I actually broke a wrench getting the front one out (so I know yamaha doesnt always follow their own specs). just curious
720raptor
are you saying the fan isnt working on some raptors? I cant say i ever hear mine come on but it doesnt seem to run hot

 

shollz: Had the same problem when I first assembled my motor. Once the motor got warm and I was on the throttle hard it would blow all my antifreeze out the overflow. Head gasket wasn't sealing correctly, Raptor720 told me that I got an old design Cometic head gasket from JE with my piston. I ordered just the head gasket from Trinity and some Threebond and I haven't had a problem since.

Regarding the thermal switch. I also wired mine to a toggle switch, I run my fan all the time. Hasn't caused any charging problems and I know the engine is always as cool as it can be.

 

Test the thermal switch. Remove it from the radiator, place it on the stove in a pan with about 3" of water. Connect a Ohm meter to the two leads on the switch. PLace a thermometer in the water and note at what temp the switch closes the circuit. Mine was 212 degrees -- if it worked at all.

I am much happier with the toggle switch -- I know when it is on and I know when I want it on.

 

If some of you guys have had a head gasket problem, I guess that is what I will try. I will order one from trinity. As far as the fan goes, I hooked it up to my light switch , since I sold my lights. It's works great.