Is there a guide for building a mb?

Discussion in 'General Questions' started by jadi929, May 4, 2010.

  1. jadi929

    jadi929 New Member

    Hey, a total noob here. I was thinking about using a motor off of a weed trimmer to motorize a bike. Is there a step by step guide to building your own? Also, for those who aren't buying a kit, is there a list of parts somewhere (for noobs like me) so it could give me an idea on how much its all gonna cost me because i don't really know much.

  2. motor_head

    motor_head Member

    no guide but once you know what you want to do we'll help you out with any questions,
    first decision once you have a motor is how you want to drive it, belt/chain or friction
    for most bike tires you'll need a ratio of about 12-14 to 1, a lot of it you'll have to figure out as you go

    really should fix the key with the 2 dots(forget the name) on my keyboard
  3. give me vtec

    give me vtec Active Member

    if you dont have the mechanical experience to already know what you want in your head... i would save the headaches and buy a kit.

    start with the bike... what kind of bike are you using???
  4. AussieSteve

    AussieSteve Active Member

    I agree. Trying to get it all together and working from the ground up would be a PITA.
    Also, a weed trimmer motor won't give you the performance that you're probably hoping for.
    If you buy a kit, much of the work is already done plus there's a large range of accessories available such as expansion chambers, high-compression heads, shift kit, carbs etc.

    There's no step-by-step guide here that I'm aware of, but there are some pretty useful 'stickies' at the top of most sections.
    Last edited: May 5, 2010
  5. srdavo

    srdavo Active Member

  6. jadi929

    jadi929 New Member

    yea thats what I thought at first, that I should just get a happy times kit. The only reason i went with the trimmer was that I see many ppl on here say that the material is cheap and stuff.

    But yea, ur right, will probly just get a kit
  7. Nuttsy

    Nuttsy Member


    Don't listen to 'em kid. You do what you want and stay away from the happy time crud--there's the real heartache and money pit. Nothing as rewarding as building your own machine. Back in the days...there were no kits; no instructions; parts; etc. Kids that were lucky enough to come up with an engine figured something out and had a blast doing it. Then, had a blast riding it; fixing what broke; and on and on.
    For parts--there is no 1 source. Figure out what you need to get this to do that and search the scooter and motor bike sites. That's cheap and informative. You are already on one of the best sites for info on building a motor bike--so search, read, and learn. One of my favorite threads is one called something like...chainsaws, and weed whackers, oh my. or some such. I read it when I lose touch with why I got into this. It's a hoot and lots of good info...oh and very long.
    Start there and learn... you are young and will accomplish much. Don't let anyone ever tell you 'you can't get there from here'. For any aspect of your life. Make your own path, and enjoy the experience.
  8. jadi929

    jadi929 New Member

    well said old man :) i'm having trouble tryin to identify the engine on my trimmer, trying to figure out how much cc it is. any ideas on where to look? i tried to find the manual for it online, but no help

    its a homelite st175g
  9. give me vtec

    give me vtec Active Member

    I admire your enthusiasm.... if you do decide to go with a kit, dont buy a chinese 2-stroke kit. Almost every aspect is garbage.

    There are very reputable kits out there that use weed whacker/trimmer/industrial motors for power and are available with or without the motor if you want to try and make yours work.
  10. SimpleSimon

    SimpleSimon Active Member

    This PDF will give you more information about your trimmer than you could ever want, I'd bet.

    The critical info is the engine model number, which should be on the crankcase. It will be either an ST-185BC engine @ 25 cc, or a GST-BC engine @ 30 cc. Either engine may or may not have a clutch, depending on the trimmer model.
  11. jadi929

    jadi929 New Member

    thanks for that pdf, either way i don't think 30cc is that good, looks like i'll be getting myself another trimmer :D or anything with a nice motor for that matter