Lawnmower Engine Retrofit?

Discussion in '4-Stroke Engines' started by grouchyolfart, May 31, 2008.

  1. grouchyolfart

    grouchyolfart Member

    Another noob question. If there's a link to an existing thread, can someone post it for me? Mahalo.

    As for starting this thread, can't blame a guy for trying to use what's on hand. Short on cash at the moment and shipping is killer from the mainland. Going to have a long wait till I'm ready for a "proper" kit.

    So....I thought I saw that one of the vendors sold clutches and gearboxs for these things? Got me a good working lawnmower powered by a 2.5 hp B&S engine that I no longer need as the wife bought me an electric one. Hard to sell and realize anykind of decent return on the initial investment so I thought maybe I could use it for my first project, if it's possible. I'd like to make this one a frame mount. Someone point me to the right vendor? Mahalo plenty....:)

  2. JohnnyLoves

    JohnnyLoves Member

    It is important to consider that with a lawnmower the powershaft coming out of the engine which you would attach the clutch too is orientated to the ground rather than on the side of the engine. It is like this on most models, if you wanted to hook a system like this up to a bicycle you would need a shaft and gear system to correct the orientation of the power shaft.
  3. grouchyolfart

    grouchyolfart Member

    Thanks JL for pointing that important feature out to me. I totally had a senior moment and forgot about the orientation of the drive shaft. :oops: :)

    Guess I'll dump it cheap, lick my wounds and bide my time till I have the money for a "proper" kit. <sigh:mad:
  4. JohnnyLoves

    JohnnyLoves Member

    I was going to do the same thing with my lawnmower when I ran into the same problem. The cost of additional parts would also be far greater than just buying everything together in a kit. Pretty much pushed me to dax's engine kit because everything was sure to work.
  5. stude13

    stude13 Active Member

    a good option for your type motor is a powered trailer. they are quite easy to build and pobably not covered by law.
  6. loquin

    loquin Active Member

    If you can find a small roto-tiller that's scrapped out, the gearbox on those things are about 300 RPM (perfect for a 26 inch wheel) and are horizontal output...
  7. muddawg

    muddawg Member

    aww heck ...grouchy,

    all you need to do to use a vertical shaft 4 stroke is create a friction drive for it
    maybe have a roller on the opposite side of the rim to balance out the side force from the drive shaft

    i agree something that uses the most common engine style would be trick !

    im gonna look into that roto tiller ide'er too

    it can be "all" be done ...its just whether "I" can do it or not ?

  8. grouchyolfart

    grouchyolfart Member

    The roto tiller idea may work, if I could find one. Not many use these out here. If so, they're not letting any go. ;)

    I'd probably have a better chance of finding a rotary type mower instead. Same engine orientation. I'll just have to keep my eyes open for one. Meanwhile, the plan is still to buy a 2 stroke 65cc engine kit, but this plan may have been set back a bit since I just couldn't pass up this deal on a Dayang retro scoot for $200. It isn't running right, but parts shouldn't cost more than what I paid. :D
  9. Jax Rhapsody

    Jax Rhapsody Member

    A lawnmower engine will run if its stood up. You can use it, its just you'd have to have that special way of mounting it to the bike. i've tilted a mower on its side and it still ran. You just need a seperate gas and oil tank. Question would me making it electric start. I'm thinkin one of the wheel motors from a power wheels car.
  10. What about using the verticle shaft as a friction drive, running against the side of the rim rather than the top of the tire?
  11. arceeguy

    arceeguy Active Member

    This guy is my hero! Check out the videos, he shows exactly how he got a vertical shaft engine to work on a motorized bike!

    I'm guessing that the engine he used had a "heavy" flywheel, as most lawn mower engines have lightweight flywheels and they depend on the inertia of the blade to keep them running smoothly. If you pull the blade off of most lawn mowers, they will be difficult to start and will not idle even if you do get them running. Another hurdle is that they often use 7/8" shafts, where common pulleys and centrifugal clutches are designed for 5/8" or 3/4" shafts.

    Shame that they are so difficult to adapt for bikes and go-karts because they are so darned plentiful. Passed by two mowers in the trash on the way to work. I bet that all they needed was a good carb cleaning to get them running again.
  12. Jax Rhapsody

    Jax Rhapsody Member

    They arent hard to use for gokarts. You just need a riding mower axle or a front axle off a fwd push mower. I seen someone made a trike out of a ridin mower on craigslist. Just think of everything being turned 90 degrees and a tilted up axle.
  13. WOW. That idler wheel on the other side. That's the secret,dawgs.
    That's the secret.
    Yea it probably has something of a flywheel.
    But whatever because IT WORKS.
    Thanks for that link "a"guy (uuh! Bad words!) :grin:

    It's videos like these that show ANYTHINGS POSSIBLE.

    All I need is a welder,some angle iron and a lawnmower engine and my trike is good to go for the front wheel.
  14. muddawg

    muddawg Member

    i knew somebody somewhere had to have done it
    just too many around

  15. grouchyolfart

    grouchyolfart Member

    Man, I was just about to go out to clean up my old lawnmower to sell at a garage sale. We cancelled the garage sale so I'm going to spend the morning taking the thing apart so I only have the engine left. :) Hey, the engine's easier to store than the whole mower. I just know someone's going to come up with an affordable kit for these sometime soon. ;)
  16. mslipac

    mslipac Guest

    how would a guy set up the carb on those engines so you can idle it low and control the engine speed...all lawnmower i ever had only have one speed as you fire it up
  17. muddawg

    muddawg Member

    different applications will have different carbs
    and many will interchange

  18. Well, my old mower is 6.5 Hp, that'll get 'er done! I wonder how many cc's.
  19. arceeguy

    arceeguy Active Member

    Some mowers are equipped with a throttle. Usually the older and more expensive models. The ones with the fixed speed usually use the same carb minus the throttle control. The "throttle" on a mower doesn't connect directly to the throttle plate on the carb, it is connected to the governor and changes the governed speed. So when you pull the cable, the throttle plate goes WFO until the engine reaches its governed speed and then it closes. This could lead to some very jerky starts! Probably best to connect the throttle cable directly to the throttle plate and bypass the governor for smoother throttle control. The holes for the throttle stop screw (idle speed adjustment) are probably in the carb, but I've seen cases where you would need to drill/tap. Might be easier to find a carb from a mower with a speed control or possibly mount a small motorcycle carb which would have many more tuning options.

    A typical 3.5HP B&S side valve engine is 9 ci or roughly 148cc. Lawn mower power ratings are merely "opinions" if you ask me because the last time I looked, the "6.75" on the engine wasn't actual "horsepower" but some vague "gross torque" rating that probably can't be compared to another manufacturers engine. Surprised to see L-Head side valve engines still being produced with the ever tightening EPA and ridiculous CARB regulations.......
  20. graucho

    graucho Active Member

    All of my minichopper builds had 6.5 hp honda's installed. 198cc Not bicycle street legal.
    Last edited: Jun 19, 2008