Anybody help please. I have a 1990 DTMX 125 and live in France. It is the old air cooled 6 volt electrics type manufactured mainly in the 70's. It is a 1990 as they were re introduced but with electronic ignition in France for a couple of years. The bike has symptoms almost like dirt in the carb. It revs freely and will hit the red line in 6th on the flat or with a tail wind. Starting is no problem. However into a headwind or a climb on full throttle but mid range revs it misses subtly and lacks power. Almost losing half it power. I have stripped and cleaned the carb several times. Checked adequate flow from the fuel tap, tried another plug and plug cap and another ignition coil. When it has this power loss you can drop a couple of gears and it will happily redline but bog down again jerking and feeling like fuel starvation even at 5-6 thousand revs as soon as you get into 5th or 6th in the 'load situation'. I have also tried moving the needle up and down by two notches on the carb piston but again no effect. Any help woukd be appreciated I love this old bike but it is driving me nuts!

Mileage?

Do you know the last time it had a top end check?

maybe it really is fuel starvation? check the flowrate of fuel from the fuel tap

Float level,

Thanks for all the ideas guys, I have found the problem. On removing the flywheel/ generator cover about 1/2 a cup of water came out! The various coils and the pulser coil were dripping. All now wsshed out with wd40 then dried. Now she is flying again.  

I thought you said it was air cooled !!  Lol , don't drink the water .