31cc Mountain Bike project

Discussion in 'General Questions' started by USAbro, May 7, 2015.

  1. USAbro

    USAbro New Member

    Hey guys. I'm new here as you can see.

    I own a diamondback outlook mountain bike and am attempting to create a friction drive bike with it.
    I have a few questions but first this is what I'm using. A 31cc 1.6hp Ryobi motor. 26" wheel.

    Questions:

    If done correctly, what speed might I achieve?
    Do I need a license to drive on roads/sidewalks?

    Will pressing the shaft against the wheel with spring pressure damage the motor (shaft or ball bearings)?

    If the metal drive pipe is smooth will it slip and not work? I'm not using a bike peg.

    Will a friction drive wear out the tire? If so, how long do you think it will last for?

    Since I have removed the clutch, what do you think the minimum speed that the bicycle needs to travel at for the engine not to stall?

    How many miles per gallon is typical?

    Oh and very important, will bolting/drilling into my bike damage the bikes frame a lot? I don't have an arc welder so too bad I guess :)

    Thanks

    Sean:whistling:


    Thanks if you can answer any of these you will be of great assistance to me.
     

  2. USAbro

    USAbro New Member

    Hey guys I got it mounted but the vibration broke part of the casing and I could just weld it back but I'm afraid that it just will probably break again as it seems to be cast iron. I can remove the gas tank and maybe mount it there but the gas tank clips on and I don't think there are any drilled out wholes as that is part of the engine block. How should I mount it or is it not worth it because the engine shaft is slightly bent by the slightest degree.
     
  3. darwin

    darwin Well-Known Member

    If the engine shaft is bent I'm afraid your motors not a good candidate for a motor assisted bike. Too many issues associated with that to mention. It's hard to bend a crank shaft are you sure that it's bent? In my experience with a 35cc Honda with a 1-1/8th roller you can get to about 22mph with some torque to go up hills but not a lot. Why not buy a Dax or Staton friction drive kit? They're not that expensive, $150 or so. You can get a HS 38cc or HS 49cc 4stroke from gas bike for about $130 and your good to go. In my experience tires last about 500 to 700 miles with using a steel knurled drive roller. As far as drilling into the frame your going to get 2 different opinions. I wouldn't do it in the rear stays as I'm of the opinion it weakens the structural integrity of the frame, others will disagree. Form your own opinion.
     
  4. USAbro

    USAbro New Member

    Yeah it is bent a little bit. I'll probably just get another weed wacker engine. Where can I get the kits you mentioned? I am trying to make this so I don't need a permit. I hear that if it cannot go faster than 20mph on level ground or more than 50cc or 1.5 break hp it's all good. But the kits on amazon are 80cc like one or two of them are 49cc but they can still go much faster than 20mph. Parents say it's fine if I don't need a permit.
     
  5. USAbro

    USAbro New Member

    lol I already drill it last week
     
  6. USAbro

    USAbro New Member

    Hey guys. I have now put the entire thing together. And before I did so the engine would start. But now the engine doesn't start no matter what I try. I replaced all the fuel lines because they were cracked and the entire thing is pressed down on the tire by large springs. It doesn't slip it just bumps and spins but never starts the engine. I have the throttle attached to the back brake cable and I pull the throttle when I peddle really hard and fast, even down a hill. Could something be just wrong with the engine? And what part of the engine creates the power to make a spark?
     
  7. USAbro

    USAbro New Member

    lol I found the problem I removed the magneto flywheel thinking it was just a fan. Does anyone know how to reattach it? Would welding maybe work?
     
  8. USAbro

    USAbro New Member

    Hey everyone I really need help. I welded the flywheel back on and realized two problems. The heat of the torch (1440 F) demagnetized the magneto flywheel. And, I didn't realize at what point on the shaft it needed to be so it's in the wrong part of the stroke even if it were to fire the spark plug, which is doesn't because it's demagnetized. However, I was going to epoxy some neodymium magnets onto the flywheel, but I don't know at what point of the stroke to put them at on the flywheel. The guy who gave me the engine/weedwacker says he has another he gave a friend who never uses it and he might see if he can get it to give to me. It's the exact same one. If he can that's great but I can't count on it so I really need to know how to tell where to mount the magnets. If anyone knows how to do so please let me know asap!

    Thanks

    Sean
     
  9. USAbro

    USAbro New Member

  10. renegade2

    renegade2 New Member

    The flywheel should not need welding. It installs with a key and a nut. Epoxying magnets on probably won't work. The flywheel spins at high speed and needs to be balanced. If you've welded the flywheel on you've totaled the engine.
     
  11. RumblingV8

    RumblingV8 Member

    Unfortunately, this is the case.
    Secondly, why would you remove the fan? Engines are built the way they are built for a reason. If it would run fine without a fan then that's the way the manufacturer would have designed it. I've never seen one of these little air cooled 4-strokes without a fan...

    Even if you were an ace welder and you got the timing right, the flywheel is no longer balanced and would vibrate badly, destroy your bearings and work itself loose, probably at high speed, and what follows would not be pretty.
     
  12. USAbro

    USAbro New Member

    Yeah I did weld it on but that's because the key and nut were stripped off somehow. I hope somehow that guy who gave it to me has another engine like he said he might because now I know what to take off the engine and what to leave on. It's all a learning process.:tt1:
     
  13. USAbro

    USAbro New Member

    When I peddle very fast nothing is off balance and the engine turns over fine, but getting the timing right is impossible plus getting it perfectly balanced also. The reason I took it off was because the way I attached the BMX bike peg, the fan wouldn't fit. And I heard it was only used because the engine was inside a plastic casing that needed to be cooled more and the constant flow of driving the bike would cool it fine. Anyways, exposing the magnets to a flame destroyed them. I've never done anything with engines before so it's all a learning process I guess.

    Oh, and by the way, it's a 2 stroke engine, not 4.
     
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