Ported 48cc!

Discussion in '2-Stroke Engines' started by stv1jzgte, Mar 11, 2009.

  1. stv1jzgte

    stv1jzgte Member

    Hi All, Have been tweaking my motor bit by bit and have heard of the benefits of porting the larger 80cc or 66cc. I wondered if the 48cc had the same prob with the piston covering the top of the port, well i pulled the carb off and sure enough it does but by not as much as ive seen the 80cc only about 2-3mm.
    So with dremel in hand i got grinding! i lowered the inlet by 3mm and widened it by more than that on both sides the exhaust i went a lil more, i only cleaned the transfer ports. Re-assembled and went for a ride.
    First difference its louder! heaps!
    Power wise its is a lil better down low but as reves climb and climb and climb it gets louder and smoother! it feels like it revs alot more. I know it sound dumb but it feels stronger also, like i wont blow it up .... famous last words!
    i set a new top speed of 59.2kmh or 36.5mph my previous was 52kmh i use to hit it like a wall every time.
    Will have to wrap better cotton insulation in the exhaust to help shut it up a bit.

  2. biken stins

    biken stins Member

    That is a nice increase. Have you tried 2 stroke packing for the muffler ? A few more holes in the tube seem to help mine out a lot.
  3. stv1jzgte

    stv1jzgte Member


    Well i allready made a new centre section, inner tube and end cap about 100mm longer, it was quiet before i ported it!
    At the moment i have filled it with fibre glass but when i have the time i will be getting the cotton insulation from mca (motorcycle parts shop) for 2 strokes!?

    This pic is the muffler as of now 11mm outlet, i have tryed 17, 15, 13mm by drilling out a nut and welding it on the end


    This is the origional centre and end cap. the peice below it is the end i chopped off a bit i drilled and then bent the holes in to direct the air to the insulation, this sits in the centre of the outer can with a sorta cone at the inlet end directing air through the tube.


    Last edited by a moderator: Mar 13, 2009
  4. stv1jzgte

    stv1jzgte Member

    whats that end cap?

    can anyone guess what the end cap of the muffler i made is???????????
  5. Zev0

    Zev0 Member

    Can anyone guess why this is in the bicycle repair section instead of the 2 stroke section? I sure can't.
  6. stv1jzgte

    stv1jzgte Member

    awe... so move it

    Wow your all over it! you should be a token administrator!
    If the real admin wants to move it im all for it! :icon_cry::icon_cry:
  7. impression

    impression Member

    hehe, i could guess ;)
  8. stv1jzgte

    stv1jzgte Member

    Ha no not you! As you can see from the lack of replys and as zevo the smart *** so eligantly put... its in the wrong section :grin5:
  9. impression

    impression Member

    so, still going strong ?
  10. stv1jzgte

    stv1jzgte Member


    Hey, yeh all is good with the motor sorta! though i have have a few problems in other areas, friday my rear mudflap that i made:whistling: snapped off (again)taking with it the left hand brake lever arm and pad, i didnt hear or see it because its so dam loud now and didnt really notice the braking loss till i got to work... "wheres my mudflap oh **** my brakes!" That fixed yesterday buzzing along the m7 i heard a loud ping! i instantly lifted my feet thinging it had blown up! still running i went back to where i heard the noise and there's my front mudflap that i made:whistling: snapped off!
    From 30-50kmh it has alot more vibration but from then on it smoothes out till it just wont rev anymore at 59.5kmh.
    All this vibration is slowly rattling my bike apart.
    The worst would have to be that because of this the float bowl needle gets itself stuck up in its seat, ive hit it with 1200 wet n dry and polished the **** outa it it still gets stuck!
    Time to upgrade to the CNS carb, though the local seller wont stock them anymore because he cannot provide any tunning data for them so i have to go elsewhere. ramble ramble ramble my fingers hurting.

    Edit update 4 hours later: chain fell off. Now looking into a spring adjustable tentioner!
    Last edited: Mar 15, 2009
  11. impression

    impression Member

    im gettign away now with not having to use a tensioner with the new frame.

    it's doing ym head in wondering why my new engine has no **** torque or power at all and maxes out @ 30km/h screaming off it's head. Same model, same batch of engine as the last one that had soo muchtorque and would do 60.2km/h on a 44t sprocket :/

    oh and STV mate, check this out.


    No. of Teeth/Cost (USD)
    --------------- -----------------
    26 to 39 / $37.50
    40 to 46 / $39.50
    47 to 53 / $43.50
    54 to 57 / $46.75
    58 to 60 / $49.75
    61 to 72 / $54.50
    73 to 80 / $67.50

    i'm thinking of getting the 26t :p but the new engine wouldn't be able to pull it, i dunno.

    maybe it needs wear in, maybe the clutch is slipping
    maybe some porting i dunno.

    we'll go for a spin on the weekend and tell me what you think
  12. arceeguy

    arceeguy Active Member

    As far as your lack of power goes, how does the engine sound as you are accelerating? Does it sound like the mixture is too rich? A rich mixture will cause lousy acceleration and limit top speed. Could also be too lean at higher revs. I have experienced this myself on all 66cc (80cc) engines. Top end sucked, and the engine bogged at WOT. If allowed to run this way without re-jetting, the engines would have blown up even with the 16:1 gas/oil mix.

    If it is revving a lot more than your other engine with the same gearing, then maybe the clutch is slipping?

    On rare occasions, I have gotten engines that lacked compression because the chrome plated bore was not finished properly. They lacked the proper "cross hatch" pattern that is required to properly seat the rings in the bore. A few quick passes with the proper style flex hone fixed the problem. (once again, a rare problem - only found two engines out of 75 or so.)
  13. impression

    impression Member

    I've tried 2 different 'barrels' though :/

    ill check for slipping clutch when the sun comes up.

    i'll also re-grease the clutch pin and bearing for the whining sound i hear when clutch is in 'drive' engaged position.