Derbi Senda Smoking after Top end rebuild!

me and my mate have just finished putting a new piston into his derbi senda x-treme 50r, and now after 5 minutes of riding, smoke is coming out of the head. fresh coolant has been put in also. whats going wrong?

 

did you bleed the air out ??

 

erm no how do i do this?

 

the top of the engine is quite high, then the out-let hose goes downwards, so an air pocket develops that the pump won't shift ......................... at the top of the engine there might be a bleed nipple, loosen it and tighten when all air is out and only coolant is coming out. If no nipple, loosen the hose to let the air escape. You might have to do this twice, so do once, run for a minute, do again.

Don't do it when the engine is hot, as the coolant will be hot, and you will get SCALDED, be warned mate.

 

im confused, there is coolant coming out the thin pipe that goes to the carb, which pipe am i loosening?

 

the hose that comes out of the head, and goes to the bottom of the radiator. If the thin pipe is leaking, it could be it over heated and developed too much coolant circuit pressure.

at worst, the head gasket has gone, and the combustion gases are pressurizing the coolant system, but you may be lucky. If when you start the engine, the hose goes rock hard, the head gasket got cooked.