Hi i have a yamaha dt 125 lc 1982,

The engine has just been totally rebuilt, i got it back yesterday and put it in today but its over heating, the needle just sits by the h red mark but it does go on the red same times but the engine doesnt feel that hot when i undo the radiator cap, i can see the water pump flowing the water through the top of the rad so it cant be that

The engine has a 180cc big bore kit on it but all the sensors are all the same from a 125

While the engine was gone i had another engine and that was doing the same thing, iv changed the rad and it stil does it..!

I cant work it out any help will be great

Thanks

I take it you have checked the sender unit, and its wiring.

Hi yep all works fine...

I think Cynic meant that the sender unit might be faulty.

I don't know much about these bikes however, based on what you have written I would say a faulty sender or temp gauge. 2 different engines with I am assuming 2 different thermostats (if they have those). Rad changed. That really leaves the hoses, temp sender unit or temp gauge. You say that the engine doesn't get that hot, and if it was, you would be able to smell it. Have you checked the hoses are not collapsing under pressure? If this isn't happening then I would guess the sender or gauge are faulty.