YFZ losing coolant...

[metalmellinium]

Ok i searched and could not find any answers. I have a 04 YFZ and seems to be losing all of its coolant out of the over flow. During my races it dumps out of the overflow and the rad is empty by the time i come in less then 10 mins. I have a bigger rad but also removed the fan and running engine ice. Heres whats done to it and i have done a leak down test and tested the rad and seems ok. WR crank athena 98mm 14.25.1 piston, bored carb to 42, G3 cam, ported polished head, dyna ignition, running on u4.2 jetted 200m 50p middle clip 2 1/2 turns Thanks for the help!

[coryatver]

Originally posted by metalmellinium
I have a bigger rad but also removed the fan and running engine ice.

might not be your whole problem but engine ice is garbage. Put in some ethylene glycol antifreeze.

[Ride1Rob]

Waterpump or head gasket. Based on the mods you have, I say blown headgasket.

[metalmellinium]

Waterpump meaning the seals on the inside? And if it were a head gasket wouldnt it make the coolant bubble in the rad? This is the 3rd or 4th ride on it with the piston and gaskets.

[metalmellinium]

And would the u4.2 be a problem being its not a high octane fuel? And does the jetting sound ok for about 500 elev?

[BakerRacing40]

start at the easy point. test you radiator cap or just get a new one.. easier than pullin the head or water pump...

[coryatver]

the water pump impeller gets scored and ruins the seals. It is a very common problem on these.
http://yfz450.theatvchannel.com/invision/index.php?showtopic=53470

But sounds like your problem is a blown head gasket

[metalmellinium]

Already changed out the cap, and i already changed out the water pump once before but that problem you linked me to was because yamaha installed the seals wrong from the factory. Its not leaking at the water pump.

[jrspawn]

Head gasket and or warped head if its been ran much without any coolant.