Hi I have just recently bought a k reg tdr 125 and it keeps nearly overheating I switch it off just before it goes into the red after about 5 mins of riding, ive fitted all new hoses as one was split and iv already checked the thermostat is opening so I cant work out why its getting so hot so quick, I have noticed that when I start the bike all the coolant is forced back up the rad and out through the expansion bottles overflow pipe at the back of the bike.

any suggestions on what is causing this problem would be much appreciated thanks.

Water pump not working

Air lock

Rad or other waterway blocked

Overheating can also be caused by incorrect timing and the likes but it sounds like one of the first 2 above.

thanks for the reply would it be best to put some rad flush through the system or is there an easier way to clear it out

A flusher may work or you could reverse flush the rad by taking it off and flowing water from a hose the opposite way to the way it runs in the bike. Normally rads don't go wrong so I would be leaning to an airlock or water pump failure before the rad.

The head gasket is leaking, thats what's wrong!

You should stop riding it or risk warping your cylinder head!

Buy a genuine yamaha one...pattern ones cant be trusted IMO...been there and got the T shirt