grim

Thanks I've removed radiator, checked the Temperature sensor, Measuring it in boiling water. Result war it went from 230 OHM and slowly down to 70 OHM as the temperature rises. My first thought then was that its defective? From what i understand, the cooling fan goes on/off. So i figured the Temp sensor also should open or closed? As we start the engine now, it gets hot fast. The fan don't start(fan is tested ok at 12v).

I've filled up cooling system, started engine and checking for pressure/bubbels in radiator. But it seams dead, usually when blown gasket you will et smoke/bubbles in radiator? Oil is also fine, no water.

Montesa World Racing 4RT engine got hot and blew out most of coolant. Refiled and noticed that the flow through radiator was non. Checked pump, OK. Checked seals, OK. No water in oil or compression leaks into coolant system. Bike has been running fine last 50 hours. After this happend the engine was low on cooland(due boil), but i also had to fill 150ml engine oil for some reason. Never used a drop before(can it be due it got hot?). So i wonder why this happen, what to look for. This is a 2012 model Future World Racing 292cc Montesa with bigger radiator ++ Fan runs ok, so thermostat is ok. Else i wonder, can air block the coolant flow?