my bike keeps over heating and i don't know why, after a short ride the temp gauge is almost in the red and the coolant in the expansion tank is bubbling its that hot, and comes out the over flow, don't think the fan works but dont think that would make it over heat
any help welcome

Don`t think it`s bad if it`s at almost red,they run really hot,and I think you`ve put too much water if it comes out from the overflow bottle

I reckon the rad cap might be knackered...stops it being under pressure and hence it boils easier.

I don't have a fan at all on my bikes- as long as I am not stuck in town then I have decent temps.

See if you can check the fan. make sure it has full rads too - if it has boiled half the top rad away it won't like it!

Broken coolant pump ?

how can i check the coolant pump? as for the rad cap how would i know if its broke just get a new 1 and if it don't do it any more its ok? put a motocross bike in front of me and i would fix it in ten mins lol

just been out in the garage again to have a play, took the coolant out and it had loads of bits of crap in it and that made my think what about the head gaskets? how could i check? compression test?

to check the water pump, remove the rad cap (when cool) and rev the bike, the level should clearly dip slightly and you can tell its moving.

if its not and looks static apart from vibes ripple then pumps fucked. if the bikes been sat for any period they can shear the spigot clean off.
problem is if they do you will have 2 large chunks of metal floating around the sump.

if pump ok, then replace the rad cap. a knackered cap wont help matters for sure.

also remove the stat housing (remove right hand mid panel, its behind there) and ensure the stat opens when boiling. if it doesnt then thats a problem,

apart from that the only typical issue is the usual knackered clogged bottom rad.