Ok I need some help here

Discussion in 'General Questions' started by Chookawatts, Aug 4, 2012.

  1. Chookawatts

    Chookawatts New Member

    Hi Everyone, I need some help, I have almost finished my motorized bike, but after a few test runs it doesn't go as good as expected. First I'll give you the specs: 66cc china motor with SBP expansion chamber and jack shaft kit, Delorto 16.16 SHA carby, NGK B6HS spark plug .020 gap and i'm now testing .025 gap, Rocksolid engines reed kit, so called performance CDI, the one with the pretty red lead (I have ordered a jaguar CDI but it is on back order and hasn't arrived yet) and it still goes slow, just checked the head bolts today and found they had been done up by a finger and thumb wrench, so I torqued them down to 12lbs, Im not sure but I would expect my head gasket would be no good now if it wasn't torqued done properly but maybe it will be ok, this engine seems to be losing power pretty quickly, I'm still on the 16:1 ratio run in fuel and my top speed is getting slower and slower 53.7 down to 49.8 and now down to 47.4. I havent tested it with the head tightened yet but I cant see that making an amazing amount of difference without a new head gasket. bare in mind the engine is still stock standard no mods to barrel or head. it doesn't seem to rev harder, past half throttle, just revs nicely to half throttle and then stagnates. has anyone got any good proven advice for me?
     

  2. darwin

    darwin Well-Known Member

    Just so we're clear your going in the high 40s and low 50s mph and thats not fast enough?
     
  3. Chookawatts

    Chookawatts New Member

    Sorry, I'm in Australia so that's 40 - 50 kms per hour, which is only 35 mph for you guys
     
  4. darwin

    darwin Well-Known Member

    I'm not an expert on HTs but if your reving fine halfway then it flattens out I'd be looking at the carb. Make sure the slide is moving all the way, floats adjusted for full movement, no restrictions or air leaks. Throttle cable has full movement etc. Theres a 100 guys here who know those carbs better than I, wait till they chime in. On the head gasket i'd just torque the bolts down and see if its going to leak or not. Once you start it up and run it you'll know. Remember the gearing will have alot to do with your speed also.
     
  5. Chookawatts

    Chookawatts New Member

    Thanks Darwin, I did make the throttle cable myself so that might be the first thing I look at, I was also thinking maybe jet size is wrong, I shouldn't have any air leaks as I used Orings, but ill check the float as well, thanks for your input, hopefully some guys with these carbs will be able to help me dial it in. well i just checked the throttle cable etc on the carby and its spot on, not sure on jet size though, I don't even know what the stock ones size is suppose to be.
     
    Last edited: Aug 5, 2012
  6. Fabian

    Fabian Well-Known Member

    Crikey, i am lucky to get a top speed of 15 kilometers per hour out of my 66cc engine, and that's with a tail wind and all my engine modifications.
     
  7. Chookawatts

    Chookawatts New Member

    I've seen these 66cc engines doing 40-50 mph so that's what i'm aiming for, I believe I need more compression better spark and the correct size jet, someone here must have a good combination
     
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