I have a dtr 125 its bogging out before the powervalve has chance to kickin it revs fine in neutral but when i ride it i have to change gears quick and will only do about 45mph

A have a yamaha dtr 125 it runs but its got no power and the valve moves but isn't kicking what could it be thanks

Fuel issue. Check air filter for dirt and petcock for vacuum leaks.

Sounds too lean to me or lacking fuel.

Partially blocked jet in carb. May have to remove / clean.

Check also that carb butterfly / piston is travelling to full open position.

I guess youwillhaveto adjust the clutch cable so as to open the plates more at the pressure plates to let the clutch plate rotate freely instead of binding thus the low rpm.
Hope this helps!

huh are you saying it doesn rev or does it bog ??

check for blockages in your exhaust.

Remove the slide from the throat of the carb, move the clip on the jet needle one notch lower. This will richen the low end fuel/air mix. - - - Simple, quick, and free.

Do it, then rate this answer as "Very Helpful". Thanks.

Hi, Being an 02 has it had a full service history? your problem could be something simple like a clogged fuel filter, so that when the revs rise enough fuel is available than lower revs. there is also a filter behind the fuel tap in the tank. the powervalve could also be clogged. another common problem with 2 strokes is the exhausts need to be de-coked because carbon build up can restrict gas flow. If you can remove the exhaust then you could take it to a garage where they will blow it out after heating it with an oxy-acytelene torch. If its none of these things get back and I will do my best to figure out where to look next. Good Luck.