how to stop my yamaha dtr125 from overheating?

I have a yamaha dtr 125 1996 i fill my bike up with water and its ok for a few days then the radiator will be empty but expantion tank will be full and overheating whats the problem please

Dan
January 2014

Use original dtr head gasket with silicone I had a after market one in my bike lasted 5 min I used the old gasket n silicone n its perfect and my bike it 33 bhp maby more so it bin the after market ones they supply you anetha ones are shit to made my old head melt its self

dtr 125 I have 9
May 2012

Hi
Did you use pattern gaskets for the top end of the engine. If you did theres a chance that the big waterway hole in the base or head gasket is not punched out properly or not there at all! This happened to me with my first dtr and give the same problem you are having, if this is the problem it will overheat very quickly and the main collant hose will expand a fair bit also.
Take your thermostat out from the small housing in the head and drop it in boiling water. It should open up quickly about 6mm. If it isn't leave it out of the bike and replace the housing and gasket. re-fill system with water and run bike . If it doesn't overheat then its your thermostat, but generally these give years of service. If its pattern gaskets you used then I would definately suspect this as the cause, especially if the bike didn't overheat before the rebuild. Yamaha base and head gaskets are about £15 for both and should always be used as they work. Definately take the other guys advice as to skimming the head flat, but you will soon know if this is the problem as they usually piss water everywhere or leak water into the combustion chamber giving extremely rough running and reluctance to rev. Hope this helps

nick
May 2008

the head gasket is leaking then these bikes suffer from cylinder heads warping through heat,you need to take the head off and then skim it by either taking it to a engineering firm of doing it yourself by laying it flat on a piece of flat glass and moving it in circular motions with some valve grinding paste between the flat surface of the head and the glass keep checking the colour of the alloy and when its all the same grey colour then its flat enough to refit and make sure you use a new head gasket too! p.s i have dont this job alot of times to dt125r s as i am a qualified bike mechanic.

adam
April 2008