Chainsaw bike

[stuffbuilder]

I didn't really think about the proper gear ratios until the end and the clutch got burned out

What kind of gear ratio were you using?

[MisterSteve124]

I think I had a 13 tooth on the engine (way too big, but smallest I could find that fit at the time) and I was just using the biggest gear on the bike, which was like 36 tooth? I think

[Mr.michael.2468]

i am one of the few that has done this, mine has a 60cc engine on it, i got it up to 40mph once, but i want to deter you now unless you are a trained machinist or have a friend's dad who had access to a machine shop. everything with a bike is a pain in the butt, the engine you'll probably get wont run at peak performance (like mine) and the gear ratio will be wrong and you'll end up pushing the bike up hills, i rigged mine to the rear cassette so i'd have a 7 gear transmission, it still wasn't right. i took me at least 100+ hours of work on it in my basement with maybe 15 design changes along the way and in the end my friends dad had to redo a lot of it cuz it wasn't good enough and he had to lathe a bunch of pieces for it. if you want to do this for a mode of transportation and not for the "fun of it" (i use the word fun lightly) your better off buying a little 50cc moped.
a couple things i noticed on your ideas that i tried:
you cant weld to tool steel that the chain saws clutch is made out of-
chain saw engines are horribly under powered for this purpose, no matter how big of one you get, you wont get past the fact that there made to slice through wood, not push some a bike along-
the main reason i bring up the power issue is that the acceleration is horrible, not even feasible to use in a traffic situation, it takes at least 30 seconds to get up past 20 mph, by then you'll have a line of cars behind you-
and even if you do get all the mechanics to work out, you still have to deal with a dumb old engine that doesn't stayed tuned and you spend more time scratching your head as the engine sounds like whoopee cushion when five minutes before it was purring along nicely.

one thing i respect you for is not going with the dumb little friction drives, those don't deserve recognition compared to the work it takes to do a chain drive

i don't mean to burst your bubble, but i originally calculated the cost to $120 it came out to more like $280 there's to many parts to the project to predict the cost. i did it as a fun project because i love doing this kinda stuff, but you really have no idea what your getting yourself into.. but if your up for a huge challenge, and want the sense of accomplishment from it (and have space in the back of your garage for it) i say go for it, i learned a lot from the project.

all i'm really saying is you cant depend on it as a mode of transportation, and that in most states its illegal without having a license on it. i take it out maybe every other week and tool around my neighborhood with it, which is fun, but by the time i go a mile the carburetor is out of tune and i have to walk it home and retune it again. the only way you can avoid this problem is with a brand new, top of the line chain saw or better yet, something like a dirt bike engine which would do a lot better.

[stuffbuilder]

I can see what you're getting at, and I am planning on running into some of these problems. I do have access to a machine shop with industrial lathes and CNC mills, so any precision machining will be done there. Where I am its pretty flat so I'm not really worried about hills and there are bike lanes so I don't get in the way of traffic. I'm also not expecting it to take off from a dead stop; I'll have to give it a little push with the pedals and then let the engine do the cruising. As for the engine I'm planning on completely taking it apart, cleaning all the parts, and then putting it back together. I've done this with other small two-stroke engines, and they work perfect now. Thanks for the advice though

[Mr.michael.2468]

sounds like you understand what your doing, i didn't know your background, if you were like me, 16, jobless and less then an expert in anything to do with engines or machining, i'd heed the warning but in your case, i'd say go for it.