CRF 450 spilling coolant, but not overheating???

I recently replaced water pump and seal after I noticed that my '02 CRF450R was spilling coolant on easy trail rides. After the water pump swap (which was successful), I noticed the same problem. It's interesting - the bike only spits coolant (I mean a LOT of coolant) after passing anything above 1/2 throttle. The bike makes this weird 'gurgling' noise, like trying to suck through a straw when your glass is almost empty. This is weird because I properly bled/ burped the radiators with coolant, and filled them to normal operating levels. The coolant spills through overflow hose. 

anyways - I swapped the radiator because I thought maybe the bike was running hot. I purchased oversized radiators, bought a 1.6 radiator cap (with a temp gauge) and bought engine ice. The bike runs very very cool - the temp gauge allows me to see this. Still, the bike shoots coolant out of the overflow after going above half throttle, making the same weird gurgling noise when it does. Bike has all of its power, top end was replaced not too long ago. 

I'm lost and don't know what is wrong with the cooling system in my bike. How do I make the bike stop shooting out coolant, and stop making the weird gurgle noise??? Any advice would help me!!! Thank you!:thumbsup:

1 minute ago, bigg_stevee said:

I recently replaced water pump and seal after I noticed that my '02 CRF450R was spilling coolant on easy trail rides. After the water pump swap (which was successful), I noticed the same problem. It's interesting - the bike only spits coolant (I mean a LOT of coolant) after passing anything above 1/2 throttle. The bike makes this weird 'gurgling' noise, like trying to suck through a straw when your glass is almost empty. This is weird because I properly bled/ burped the radiators with coolant, and filled them to normal operating levels. The coolant spills through overflow hose. 

anyways - I swapped the radiator because I thought maybe the bike was running hot. I purchased oversized radiators, bought a 1.6 radiator cap (with a temp gauge) and bought engine ice. The bike runs very very cool - the temp gauge allows me to see this. Still, the bike shoots coolant out of the overflow after going above half throttle, making the same weird gurgling noise when it does. Bike has all of its power, top end was replaced not too long ago. 

I'm lost and don't know what is wrong with the cooling system in my bike. How do I make the bike stop shooting out coolant, and stop making the weird gurgle noise??? Any advice would help me!!! Thank you!:thumbsup:

Sounds like combustion gasses are going into the cooling system and over pressurizing it.

Most likely a head gasket issue, you could try re torquing it.

But you probably need a new head gasket.

Or you could even have a cracked head or cylinder.

I agree with the blown head gasket idea, but re-torquing it isn't going to do anything except over tax the threads in the cases. Pull the head, replace the gaskets in the top end. These things use a multi-layered head gasket. When they leak, that's it. They're done. If you examine the head gasket, and head/cylinder closelly, you'll be able to see where it was leaking (if it was leaking there). It's not all that unusual to blow the head gasket when the engine gets over heated. A bad water pump seal allows the loss of coolant, and a secondary issue arises.

On 3/11/2018 at 2:36 PM, Shawn_Mc said:

I agree with the blown head gasket idea, but re-torquing it isn't going to do anything except over tax the threads in the cases. Pull the head, replace the gaskets in the top end. These things use a multi-layered head gasket. When they leak, that's it. They're done. If you examine the head gasket, and head/cylinder closelly, you'll be able to see where it was leaking (if it was leaking there). It's not all that unusual to blow the head gasket when the engine gets over heated. A bad water pump seal allows the loss of coolant, and a secondary issue arises.

I ordered a new gasket kit for the top end and I'm planning on replacing the old one in about a week. If the cylinder isn't cracked and seems to have little wear (along with the piston) would it be acceptable to just replace the gaskets? I did a top end on this thing less than 30 hours ago and its still running like a top, so I'd personally like to save the money of replacing the top end if I don't need to.

I was thinking of maybe replacing the rings on the piston at the least, but I don't know if that is necessary either.

Sure, you can just replace the gaskets. That's called a fix, as opposed to freshening it up. You could replace the rings if you wanted to, also.

I would order the rings.

I would take it apart look at the piston if it's worn I'd replace it.

I would also lap the head and cylinder. 

I would also re torque the head after the first run. Some people say you don't have to with a mls gasket, I mostly agree, but I still like to just for good measure.

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