Billet 115cc HT

Discussion in 'Spare Parts & Tools' started by RCcola55, Feb 28, 2010.

  1. RCcola55

    RCcola55 New Member

    I am in the process of reverse engineering the 66cc HT motor just for the heck of it and at the same time redesigning it with a friend to be 115cc's. This new motor would be an all billet case, jug and head, use new "stroker" crankand billet rod, redesigned ports and better piston. We expect the motor to make up 10hp maybe more. Most of the parts would even be able to swap into a factory case so there is a possibility it can be made into kit form. I am just testing the waters for interest, and once the first prototype is made we will have a more real world cost. Let me know what you think!
    Last edited: Feb 28, 2010

  2. Fabian

    Fabian Well-Known Member

    My credit card is waving in the air.

    If you produce a reliable 115cc (why not make it 120cc and use a proven Husqvarna 3120 chainsaw piston) and if it's available for purchase, i'll be standing in line with hundreds of other people waiting to put money into your pockets for a serious bicycle engine.

    So long as it bolts up to the SickBikeParts Shift Kit,

    i'll only be happy when i have a 120cc engine in my hands.

  3. RCcola55

    RCcola55 New Member

    Thats an idea! Those chainsaws produce around 8.5 hp and with proper tuning 10-12 is very easy. We will sit down and experiment with that design in solidworks and see is it is doable. Our goal is to not redsign the wheel here, but make enough improvments and turn out a quailty product that will last!! We want this motor to be able to use many of the aftermarket products out there, that away people can continue to make this hobby grow.
  4. Fabian

    Fabian Well-Known Member

    Hi RCcola55

    If you are going to design a replica engine, it would be advisable to keep identical external dimensions and also bolt hole threads and dimensions for the bottom end so accessory parts designed for the current Chinese bicycle engine can still be fitted.

    My 2 cents worth,

    1) Design the bottom end to use crankcase reed valve induction and eliminate cylinder intake ports.

    2) Design the cylinder to use boost ports.

    3) If possible, look at the idea of a wet clutch system to improve primary gear life and also to reduce gear noise.

    4) Give thought to engineering an electric start (add-on) option.

    5) A good point of engineering reference would be the design of any of the current 125cc dirt bike engines (Honda CR125, Yamaha YZ125, Suzuki RM125, Kawasaki KX125).

    6) An even better piston option may be to use a piston from any one of the above manufacturers or to use the Husqvarna 3120 piston.

    7) Design a correctly balanced and manufactured crankshaft using similar design principles to that of the above manufacturers.

    8) Design a method for reduced cranking effort when pedal starting the engine with high compression levels. I've suggested the use of a readily available compression release valve but any engineering solution that achieves this goal would result in a satisfactory outcome.

    Cheers Fabian
    Last edited: Mar 1, 2010
  5. Fabian

    Fabian Well-Known Member

    There is also another option.

    You could team up your intellectual efforts with the guys from Pirate Cycles who are designing a replica engine themselves, although in the standard engine capacity of around 70cc.

    Otherwise you could approach SickBikeParts or Manic Mechanic and see if they have provision to work with your engineering abilities.

    Just some thoughts over a cup of coffee.

    Last edited: Mar 1, 2010
  6. Fabian

    Fabian Well-Known Member

    My biggest bugbear with these engines is their lack of low rev torque (2000 to 3500 rpm) - something that's easily cured by doubling the cc to around the 120-ish figure.
  7. RCcola55

    RCcola55 New Member

    The reed valve idea has been thrown around, but we have to gain a little more understanding in order to adda feature like that, I worry though that it may add too much to the crank case dimensions, as one of the best features of these motor is there size and simplisity (sp?). The goal is to keep it as close external as to the original motors as possible, while adding displacement, dourablity, effecentcy. The motor would be balanced and "bluprinted" in order to help with the above mission. Keep the ideas coming we are open to any suggestions!
  8. tacoshell4

    tacoshell4 Member

    fabian jumps ship quick i see
  9. Neon

    Neon Member

    I love the idea of a good reliable, powerful engine that will snap my axle when i hit the throttle, and still be able to fit it into my bicycle. My only thought is keeping the cost down as low as possible, if it ever comes to market. I just couldn't justify paying any more than 20% for an just an engine. Low cost was the reason i grabbed a kit in the first place.
  10. Fabian

    Fabian Well-Known Member

    Gees, i could quite happily pay $1500 for a 2-stroke bicycle engine that works to perfection; comes with programmable electronic fuel injection and is easily rebuildable and backed by a fantastic warranty.

  11. tacoshell4

    tacoshell4 Member

    thats good to know fabian. i'm just messin with you.
  12. tacoshell4

    tacoshell4 Member

    no programable fuel injection on the pps motors sorry
  13. 210061741

    210061741 Guest

  14. RCcola55

    RCcola55 New Member

    We have ran into a problem with cylinders liners, orginally the motor was designed to use a honeable liner for better ring sealing, but the set up cost to have liners machined for ports is out of reach from our start up budget. Is there anyother ideas out there for a process of lining the cylinder?
  15. 210061741

    210061741 Guest

    Hire JIM AKA Manic Mechanic AKA Creative Engineering to do it.

    We did.
  16. RCcola55

    RCcola55 New Member

    would he be able to do any of the 5-axis cnc milling for it as well?
  17. azbill

    azbill Active Member

  18. AussieSteve

    AussieSteve Active Member

    I saw the axle-snapping comment on the last page.
    I reckon that with a 10HP engine, axle damage would be a distinct possibility.
    Apart from potential axle breaking/bending with a standard single-speed setup, not sure about 10HP with a shift kit and normal bicycle drive-train, either. Rear freewheels, chains etc wouldn't last long.
    (I'd love 10HP, but the bike wouldn't be so happy.)
  19. Fabian

    Fabian Well-Known Member

    I agree with Steve - 10 horsepower would most likely result in component failure of the bicycle running gear, and i'm not sure how the Shift Kit would cope with that level of power being forced through the system.

    All i ask for is a good 5 horsepower with a flat torque curve starting from 2000 rpm with a 120cc engine that's been detuned to give exceptional low rpm torque through cylinder port timing optimised for those revs.

    There is another issue and it's one of safety.
    10 horsepower would make a pushbike capable of 60 miles an hour (100 km/h).

    Now most of us are responsible people but you can guarantee that there will be some idiot or idiots who try to go 60 miles an hour on a pushbike and get themselves killed.

    5 horsepower with a monster torque curve would be perfect!

  20. RCcola55

    RCcola55 New Member

    5hp should be no problem at all with an almost double displacement 10 was just a number we wanted to shoot for, and with proper port timing and a reed system the torque curve can be dialed in exactly, although I would like to see this motor to be able to spin 10k, all of which is very obtainable with enough reasearch and modeling.