My first build. I have some questions and some pictures for you guys

Discussion in 'Rack Mounted Engines' started by The PlacenteR, Feb 16, 2011.

  1. The PlacenteR

    The PlacenteR New Member

    Hey guys. My name is Marc. I just got myself a bike today which i plan on making a rear mount for a craftsman engine off of a weedwacker.

    first of this is the user's manual for the exact engine I have.

    I picked up this bike today off of a guy from craigslist for 10 dollars.

    I plan on putting this engine into a milk crate on my rear rack.

    Here are some of the close ups I have of the engine.

    I Am hoping to get around 25 to 30 mph out of her. I'm also not exactly sure how I can get my 7500 rpm engine geared to get me that.
    The biggest problem is that I do not know how to mount a sprocket to the clutch of of the weed wacker I have. Any input is extremely helpful. Thanks in advance.
    Last edited: Feb 16, 2011

  2. professor

    professor Active Member

    Hi Marc, there are very few weedeater powered bikes that I remember here. That engine is really not suited for what we do. They usually have only one main bearing- not designed for side loads. Tiny clutches and very little power too.
    Take a look in the home built section of the site and see if you can find any.
    Cruise around the site- you might come up with someting better.
  3. Tanaka40

    Tanaka40 Member

    The engine is a Ryobi copy and the clutch is on the pull start side. Not easy to adapt. Buy a old Bladez powerboard w/40cc engine and a Golden eagle bike engine kit and you will be set for less hassle
  4. BentTooner

    BentTooner Member

    Hi, Marc
    I built 2 home made friction drive, motorized bikes with that same engine (Ryobi 31cc 2 stroke). The clutch is a bit weak for a MB so I chucked the clutch, found a BMX foot peg that had the same threads as the crankshaft (3/8" x 24 TPI) and used the BMX foot peg as the drive roller. Then, I simply pivoted the friction drive up and down (on and off the rear tire) with a brake cable attached to the drive housing. It cost almost nothing.
    I can explain more if that's not clear or helpful. The engine worked great. It got 225 MPG and my top speed was about 25 MPH.
    The pivoting of the drive assembly on and off the tire is a bit tiresome and tricky so I finally went to a friction drive kit from BMP and a used Robin 35cc 4 stroke engine from Craigslist. It has been a dream.

    Good Luck!
  5. bluegoatwoods

    bluegoatwoods Well-Known Member

    Good luck with your build.

    I'm sorry to be a wet blanket, but I'm going to chime in briefly on the safety issue. I would urge you to reconsider your target speed. I wouldn't operate any bicycle at 30 mph. Not more than, say, 50 ft. anyway.
    If you had an average speed, over several miles, of 12-15 mph you would still get where you are going with reasonable efficiency but much more safely.

    Have fun.