Hi i recently rebuilt a 1977 DT100 and it was all working fine then 2 weeks before its MOT it decides to develop problems. The bike will run but only if throttle is applied and the engine doesnt like it its also spewing out white smoke and it smells rather strong of something but im not sure what it is and if i go more than half throttle it dies and it is impossible to pull away. any ideas would be highly appriciated as i really want it to pass as this is my first build

You'll probably get a better response from the folks if you post an intro in the New Member section. I always thought white smoke was a sign of transmission fluid or antifreeze in the head, but on a motorbike I'm not sure. Others here will have a better idea. Good luck!

What does the gearbox oil smell like.

If it was a full engine build there is a little o ring on the crank that gets forgotten and can cause this.

either the 'O' ring Cynic mentioned or the RH crank seal ?

i looked at all them but i think its my airbox restricting the airflow and its trying to run on pure petrol and 2stroke also its making a horrible noise like its really struggling and the second i let the throttle off it dies, tempermental 2 strokes eh

im thinking about upgrading to a K&N filter anyway get some more air in and upjet the carb

hi there it sounds to me u could be low on water or your head gasket is on the way or low on two stroke oil or your carb is playing up and also check up your engine oil.

engine oil and 2 stroke are fine and its air cooled so no water and the head gasket is a nice and new same is my carb