Yes, its a jetting question, sorry!

Discussion in 'Scooter Tuning' started by Buzz, Apr 1, 2017.

  1. Buzz

    Buzz Active Member

    Messages:
    446
    Hi.
    History:... gilera dna50 running on a 60jet, ran well but slowed drastically on hills.
    Now:.... I had reason to strip and rebuild the engine, New crankshaft, piston, head the lot. Fitted a new aftermarket stage 6 exhaust. Carb and air box are standard.
    Wouldn't fire at first but some easy start spray fixed that. The scooter ticked over at 1500 or thereabouts but died after 5 minutes. Would only restart using easy start spray.
    I put in a 63 jet. Standard is 56. Only fires with easy start then ticks over nicely for a good 10 minutes before dying.
    Carb idle screw does nothing to change the tick over, sits at 1500, runs for 7-8 minutes and dies
    Airscrew makes no difference to engine.
    Bike revs to 7000 rpm but seems to stop there. (On stand, not tried riding as I have a flat tyre)
    So I need to jet the carb so the idle screw and Airscrew actually make a difference and get it idling higher.
    I need the bike to fire without easy start spray.
    I need to get it revving over 7000. When I do throttle up, if I blip it then it stumbles but if I twist smoothly and slowly it climbs to 7000 and sits.
    Any advice welcomed. I'm thinking either throttle needle needs adjusting or upjet main jet further. 63 is about 12% over 56 standard. Or am I needing to lean it out more and drop to a 58.
    Thanks
     
  2. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

    Messages:
    1,850
    Rides:
    Piaggio Skipper
    not ideal but pull off airbox, start it up with easy spray and get ready to block the carb airbox inlet with a few fingers when it starts to stumble and die.

    when its starts to die semi block the airfilter inlet and pop the throttle a bit ? does the bike come back to life , if YES your running lean even with airbox so require a slight upjet.

    burping/stumble when your bashing throttle you aint got the jet right, its nearly there but just slightly off.

    blow out pilot jet and pilot jet port ( 0-14 throttle is pilot jet - idle mixture setting )
    needle setting = 1/4 to 3/4 throttle area
    mainjet = 3/4 to wide open .

    good way is tipex the throttle grip and the throttle clamp on the handlebar 0 -1/4 - 1/2 - 3/4 - wide open and then split those four marks again.
    it gives your eye and head a known point on throttle, ie sluggs downwhen its at 1/4 and /34 markings , but flys when when its on wide open . thats saying the needle seting is an area to look at.

    standard jet 56 a 10% upjet would be a 65-66 jet , i would say your a bit lean still
     
  3. Buzz

    Buzz Active Member

    Messages:
    446
    Thanks, i've got a spare 68 so ill try that, reclean the idle jet and try again. Ill let you know the results.
     

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