Bottom end porting help

Discussion in 'General Questions' started by skyash, Sep 14, 2016.

  1. skyash

    skyash Active Member

    This is a 49cc big bored 44mm look in Side . what I would like to know is how does the petrol flow is this area always full of petrol or does the crank feed every turn out of a hole. thay say to match the cylinder with the bottom but it looks like I could open it up the hole area take some metal off here there even open the gap around the crank I don't know ... anyone know?
     

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  2. jaguar

    jaguar Well-Known Member

    just make sure there are no ridges where the cylinder mates to the crankcase, in the transfer area.
    even that may not be necessary unless your engine is ported to rev higher than 9000
     
  3. skyash

    skyash Active Member

    Yeah it's meant to hit 12000rev and it's so nice in Side it doesn't need anything really but if I can get a bit more out of it then y not .do you know how the fuel flows to the transfer ports from the bottom with next to no gap around the crank
     
  4. Arty

    Arty Active Member

    I've wondered about matching up the crankcase to the bottom of the cylinder too. In my case I would have ro remove quite a bit of material from the crankcase, but am worried that it would increase the crankcase volume too much - rather like the opposite of stuffing the crankcase. - Any opinions?
     
  5. Steve Best

    Steve Best Active Member

    I think you have the right idea Arty, and I agree with Jag that it really doesn't matter if not reved.
    I've played with mine, matched the case and cylinder, no difference seen.
    Even matching a very poor gasket was unnoticable in hillclimb performance.
    Theoretically it should work better matched, but I could not feel an effect from the work I did.

    As for where the petrol and air flow, from the crank center space Skyash.
    The transfer troughs look good on this engine Skyash. No deeper than the crank cheeks.
     
  6. skyash

    skyash Active Member

    Thanks everyone.so if I leave the bottom alone.now the boost ports I have 2 it sounds like to me that thay increase the pump action when the piston go's down.so by deepening them it should increase air fuel hence more power.?
     

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  7. jaguar

    jaguar Well-Known Member

    the rear boost ports have an ideal size. If you go over that size then it lessens power.
     
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