Weak mixture, Carb float height



  • Finally got back to trying to get the DT to run nice but it seems like it is running really weak.
    I start it on choke and it seems ok but as soon as I put the choke in it wont seem to hold a steady rev and if I blip it, it wants to rev away madly for a couple of seconds then will die unless blipped again.
    It just seems like a really weak mixture, I moved the needle down to one notch from the bottom but it didn't seem to make much difference so I have the carb off to check the float height which according to the Haynes book of words should be 21mm but mine is probably about 18mm - but my float does not look like the one in the book and I can't see where you are supposed to measure to.

    How do I post pics on here?



  • Sounds like an air leak to me.

    Crank seals, or inlet tract.

    There is a guid on how to post pictures, use the search button.

    Item moved to correct section, please don't post specific questions in general discussion!



  • Sorry wasn't sure where to post it.
    Yes, I did wonder about an air leak but It's just been rebuilt with new bearings, seals etc. if it was sucking past the crank seals on the clutch side wouldn't it eat its own clutch oil and smoke? could be the other side.
    Don't think it is leaking on the inlet anywhere as it's all fairly good.
    My float is like this one http://www.ebay.co.uk/itm/Yamaha-NOS-AT2-AT3-CT2-CT3-DT125-MX175-Float-314-14185-00-00-41-/181056072162
    what point on the float do you measure to?



  • The float affects how much fuel is in the bowl. The fact it's idling high and running lean tells me it's too much air.

    The generator side could be sucking in air which would explain why when you rev it seems to go away by itself.



  • I wonder if it's possible to remove the generator side cover run it and squirt some WD40 at the crank and see if it makes any difference.
    Might try that tomorrow.
    Wanted to get the float height set so I could eliminate that, it looks like it is set too high so should be rich if anything.



  • @Raydt Carb gaskets? Choke seal, correct pilot jet? visual inspection will tell. But all things I would replace.

    Investigate the crankcase last, then you can be sure.



  • @Raydt Yeah that's how you would test.

    In fact WD40 everything whilst it's idling high will tell you if its an air leak.

    Some times it can be something simple like throttle cable sticking too high.

    Again I was just under the impression the float shut off the fuel to the bowl.

    But obviously it's it's too high it'll shut off the fuel too early, and too low will cause it to overflow.