• Hi I’ve got a issue with my mates 1997 dt125 when he has the power jet connected the it won’t rev past 8.5k when removed it does the same but if he blocks both ends it revs all the way any ideas

    Thanks Matthew

  • Hi , Matthew . I had the exact same problem as you. My temporal solution was indeed to place a clip in the tube of the power jet, thus fully restricting it and fitting a 210 main jet. Even then, on full throttle I was running on the rich side, which made the engine to bog and not go above 8k rpm.

    I managed to fix it some days ago. I will make a post with pics on the whole procedure sometime around the next month when I will have the time, but here’s some things I did to look into:

    • Fully clean the carburetor body and jets using an ultrasonic cleaner.
    • Replace all the O-rings with new ones.
    • Replace the needle valve with the seat with brand new ones.
    • Adjust the float height to the Hayens manual specifications.

    After the rebuilt I went from running rich and having hesitation on fast openings of the throttle to actually running a tiny bit lean with crisp response .

    *The lean is probably due to the 210 main jet I’m using instead of the factory 240 one. *

    If you haven’t changed any of the jets, I think the above steps will help you.

    Also be sure to make a plug chop using a new spark plug to verify that you are not running overly lean or rich before and after the rebuild .