Cheers Idle, when I built the bike the engine had a high flow water pump cover but was fitted with the standard impeller, I was told this would work fine and would flow more water than standard. Had trouble with boiling over while waiting to go out on track, no kick or electric start, absolute beast to bump start. The bike runs around 75-85°c on track. Talking to a customer who services and builds track car suspension he said without doubt the extra space behind the oversized cover was causing cavitation.
I fitted a standard cover today, a weak mixture of Water Wetter and bled the air out. The radiator cap is under the tank, the radiator lower than the head bleed screw so I lay the bike over to shift the air.
A sweltering 16°c here in Wales today, I fired her up and warmed the motor up to 70°c, turned the computer fans on and just let her tickover. 15 minutes to get to 114°c when it started to spit a drop out. 45 pilot jet and a 1.6 bar radiator cap. That's a bit hot I know but I needed to try it! The temperature sensor is inline just between pump and radiator.
