More power!

Discussion in 'Motorized Bicycle General Discussion' started by Matt117, Feb 15, 2016.

  1. Matt117

    Matt117 New Member

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    I have a super rat 66cc motor and im looking for some serious power, can everyone please post what they have done to there bikes and any recommendations for me.
     
  2. Tyler6357

    Tyler6357 Member

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    Some things you can do to increase power are:
    - replace stock exhaust pipe with one with an expansion chamber
    - replace stock carb with one that with more fuel flow
    - replace stock head with a high compression head
    - porting the motor- intake and exhaust manifolds, drill piston, etc.. there is a right way and a wrong way to do this, make sure you do it correctly.
    All of these things are discussed at length on this forum, use the search function to research them. Also, the more power you add the more vibration you will get and the more speed you will have, make certain your frame and brakes can handle it!
     
  3. crassius

    crassius Well-Known Member

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    I've seen folks spend hundreds of dollars and weeks of time getting more power out of these - most get maybe 4 or 5 extra mph out of them. If you want real power, get a different motor like morini or arrow.
     
  4. Agreen

    Agreen Member

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    Step 1 is to run 3 or 4 tanks of fuel through it to get the rings seated. Lots of people neglect that step.

    Now you need to decide where your desire for speed and your mechanical ability meet.

    If it were my engine, I'd:
    -Tear it completely apart
    -Balance the rotating assembly
    -Gasket match the transfers
    -Reshape the intake and exhaust ports
    -Clip the bottom of the piston at the intake to where it opens at 60 degrees after bdc.
    -Expansion chamber exhaust (modified KTM 50, not some banana pipe POS)
    -Fred head (CR machine)
    -19mm walbro diaphragm or 19mm Mikuni (PZ19 is the cheaper clone) carburetor

    Since it's a 66cc engine, it will have the torque. Change the rear sprocket to a 36t. You'll have to pedal a little faster before engaging the clutch, but I believe in you :D
     
  5. Matt117

    Matt117 New Member

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    Would you recommend changing the jetting or buying a new carby completely?
     
  6. Agreen

    Agreen Member

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  7. 2door

    2door Moderator
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    Before you start making the bike faster, make it safer. Too many new builders spend time and money trying to get more speed and power when they should be looking at their brakes, bearings and frame integrity. Make sure you can stop the bike before making it faster. Assure the bearings, rims, spokes, tires and especially the brakes are up to the task of more speed.

    Remember. It's a bicycle, not a motorcycle.

    Tom
     
  8. gokart25

    gokart25 Member

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    buy a motorcycle
     
  9. Compulsive Tinkerer

    Compulsive Tinkerer New Member

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    Motorcycles are expensive. So is insurance. What if he can't afford a motorcycle. There are plenty of ways to go a little faster on these bikes.
     
  10. Tyler6357

    Tyler6357 Member

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    I agree, and there is nothing wrong with asking. I think the easiest upgrades are the expansion chamber and getting a smaller tooth rear sprocket. These are simple and provide a noticeable performance upgrade.
     
  11. sbest

    sbest Member

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    I think the real sprocket test is "will it go up ALL the hills?"
    If it won't go up the hills and start away without a lot of pedaling, the smaller sprocket ain't gonna be fun.

    Steve
     
  12. Tony01

    Tony01 Active Member

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    That's right.. don't take this info lightly.. once you start breaking 30mph on a regular basis you should upgrade the hubs to sealed bearing, tires to higher pressures. at least 40psi, have a good quality front brake like a disc or drum, and at least some kind of rear brake. Nothin' like the ol' cager not seeing you and pulling out in front of you while you're doing 45mph on the expressway.
     
  13. Agreen

    Agreen Member

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    45 on the expressway!??!

    Allow me to edit the info about the 19mm carb. It seems like it's good for low end torque, but it's probably not the best for speed. I'm working the kinks out and I'll post results on the proper carburetor selection.
     

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