Engine Trouble best engine 50~80cc

Discussion in '2-Stroke Engines' started by 2smokebiker, Mar 5, 2014.

  1. 2smokebiker

    2smokebiker New Member

    Just wondering if the ktm gp50r on thatsdax.com is a good engine and a good buy? It's about 500$ but comes with the carb which I think is a 21mm D-slide. What is over ppls take on it? Thanks

  2. jaguar

    jaguar Well-Known Member

    If it's designed to deliver only high RPM power and its only one speed then don't get it.
    One speed bikes need a broad powerband.
    Hopefully someone that has one can tell us what it is like.
  3. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Save Save yourself $200 by buying it direct from China.

    Only $301

    Developed from KTM50 Senior Adventure bike's engine---
    1) Engine type: single-cylinder, 2-stroke, air-cooled
    2) Piston displacement: 49cc
    3) Bore x stroke: 39.5 x 40 mm
    4) Max. power: 9HP/9500RPM
    5) Max. torque: 7NM/11000RPM
    6) Compression ratio: 11:1
    7) Ignition: CDI
    8) Spark plug: NGK BP7HS
    9) Carburetor: diaphragm
    10) Air filter: polyurethane foam(built on the KTM50 bike)
    11) Start mode: KICK start
    12) Clutch style: centrifugal automatic
    13) Average fuel consumption: 610g/kWh
    14) Dimensions: 270x220x250 mm
    15) N.W/G.W: 8.4kg(with carb) /10kg
    16) Packing Box: 290x285x375 mm
  4. keatonx

    keatonx Member

    Peak torque at a higher rpm than peak hp? Must be labelled wrong because that's impossible (hp=torque in ft-lbs*rpm/5252)
  5. jaguar

    jaguar Well-Known Member

    9500RPM peak means it is a race engine, not made for street use.
    9hp means it has peaky power, all at top RPM.
    buyer beware!
  6. 2smokebiker

    2smokebiker New Member

    Ok, thanks for the warning Jaguar. And thanks for the source link, info and tip MotorBicycleRacing.

    It does seem high in the rpm dept. But may still be usable, especially if it is possible to modify or somehow get more low end PWR (although I have no idea how I would do that).

    It seems like the carb in the list is not the same. i.e.a diaphragm carb is not a D-slide carb.

    $123 + 16 ship from UK on ebay looks same.

  7. 2smokebiker

    2smokebiker New Member

    seems like I should just get your CDI jaguar. But my engine isn't a grub it's a Skyhawk 66cc. It has a dragon on it too, I think.
  8. 2smokebiker

    2smokebiker New Member

    okay maybe this is the right carburetor?anyone else?
  9. 2smokebiker

    2smokebiker New Member

    What happened to all my other posts?
  10. 2smokebiker

    2smokebiker New Member

    MotorBicycleRacing: Thanks and: Would the Morini engine be better? Which do you think would be lighter?
  11. jaguar

    jaguar Well-Known Member

    maybe sucked into a back hole :cool:

    Carb looks good but how are you going to adapt its 35mm diameter to the 19mm diameter of the stock manifold?

    If you buy a Mikuni I can sell you an adaptor
  12. 2smokebiker

    2smokebiker New Member

    Ok thanks jaguar for the warning. About the rpm
  13. 2smokebiker

    2smokebiker New Member

    maybe the problem is I've been posting quick reply instead of reply to thread?
  14. 2smokebiker

    2smokebiker New Member

    I'm probably going to get your CDI soon for a Skyhawk 66cc engine if it will work. But I'm not sure what piston pin to get titanium or drill mine out.

    I'll make the carb adapter for either engines out of Delrin/Acetal I suppose.

    What do u suppose is easier to get parts for morini or ktm?
  15. 2smokebiker

    2smokebiker New Member

    Also jaguar, should I drill the holes in my piston to help reduce the vibs (Skyhawk 66cc)? Ramp the crown (at transfers)?
  16. 2smokebiker

    2smokebiker New Member

    Hmm, no more replies. Was it something I said?
  17. FurryOnTheInside

    FurryOnTheInside Active Member

    Probably! Your last post was directed at one member, and the previous post asked about Morini and KTM engines which aren't exactly the most popular so not many people would have experience. Also there's not been a lot of members online in the last couple of days.

    I can tell you that I'm planning to get the titanium wrist pin. It is titanium and I love titanium lol. It is hollow too IIRC.

    Drilling hole in the intake side fo the piston is a mod that goes hand-in-hand with fitting a reed valve. Only drill holes if you are using a reed valve. (someone correct me if I'm wrong!)
    You won't be reducing piston weight by a huge amount by drilling these holes as aluminium isn't very dense anyway. The advantage would be the increased flow of intake gas mixture. (A reed valve obstructs flow, but the holes increase the time allowed to get the gas mixture into the crankcase. Someone correct me if I'm wrong!)

    I'm not sure Delrin can take the heat. I never read about Acetal. I think the RSE thermal isolation spacer is Meldin IIRC.
  18. jaguar

    jaguar Well-Known Member

    Drilling additional holes in a piston to make it lighter only helps a very little.
    The titanium pin makes a noticeable difference but if it still vibrates too much you have to take the crank out and makes the balance holes bigger.
    Only if you switch to a higher topped piston or have lathed down the base of the cylinder (to lower ports) can you get away with making transfer ramps. Otherwise they increase the transfer ports duration too much.
  19. 2smokebiker

    2smokebiker New Member

    ok, I ordered the CDI, but was wondering what coil to use. One for a KDX200 or for a CR80, CR125? And I'm planning on using a Nology brand coil. So what is the ohms? 0.3, 0.6, or 3 ohms? Thanks
  20. jaguar

    jaguar Well-Known Member

    best coil is original Honda for any of their CR models.

    But if you are set on the Nology then get the one with .6 ohms.