New with lots of questions

puretexan2 · Jan 21, 2011

Hi I'm new here and I have several questions. I can build any kind of bicycle frame , and I'm wondering why I haven't seen a rear engine mounted on a custom frame? Also why all the belt to chains and jackshafts. Is there a problem with doing like a motorcycle, and running from the motor to the back wheel with just a centrifugal clutch? I found an edger, like new with a 3 1/2 hp Tecumseh motor yesterday at a garage sale for $20 and it seems like it would be something good to start with. Any cons? Thanks in advance

Goldy · Jan 21, 2011

Its all about getting the right ratio...that's the reason for all the jackshafts etc. Yes, you can run directly from the engine to the wheel, especially if you are going to use a belt...you would be hard pressed to find a sprocket big enough for the rear wheel to do it in one shot with a chain.

Gator Wrestler · Jan 21, 2011

I don't know about the frame. The reason for the jackshaft is to get RPM reduction and torque increase. Even for a powerful engine like the 5HP 4 stroke a drive ratio of about 10 to 1 or 14 to 1 will be needed to get the desired results. A motorcycle uses reduction too in the treansmission.
That engine you have should be useable.

puretexan2 · Jan 21, 2011

Thanks guys. I have tried to do a mass amount of reading to learn the answers to all my stupid questions. I know everybody that has already learned all of this through trial and error ,hate for new people to ask the same old questions. Its hard to start a new endeavor and learn all the stuff quick, that has taken yall years to find out. I hate to make a mistake , but I know it will happen. I do appreciate it. I have seen a few people do the old style trick where they stick a 24'' rim next to their 26'' rim and use it as a big pulley. I need to build a frame and see how the motor will best sit on the frame before deciding on how to hook it up. Thanks again.

curtisfox · Jan 21, 2011

Under DIY check out page 2 Briggs Bike Build. Is one with a briggs, and under general discussion,My Next Custom Build..........Curt

Goldy · Jan 22, 2011

Why don't you have a look at vintageprojects.com and check out the motorized bike section, there are some ancient articles from Popular Mechanics on there that might give you some ideas...use a centrifugal clutch and it gets even simpler...you can check out 'wanna be' under DIY, I used it to get one of my buddy's builds on the road.

puretexan2 · Jan 22, 2011

Man Goldy you build turned out super. Lots of neat ideas. Did you post build pictures anywhere else. I would love to see some closeups of the belt hookup and how you did the rim to the back wheel. Very nice

Goldy · Jan 22, 2011

Didn't post any pics of the build on that one, but it was pretty much as per the set up on the website I gave you...we went with a gate and lever on the tank rather than a foot clutch...trying to get that 'old timy' look...a centrifugal clutch would have made it a lot more user friendly though (just point and shoot). The belt driven rim can be simply brazed to the rear rim, but I used 3/8" spacers all round to get the driven rim away from the main rim to clear the balloon tires. The engine you have ought to work well with about a 12-1 ratio.

lowracer · Jan 22, 2011

Puretexan2,
I've got 2 MB's that go straight from the engine to the driven wheel via V-Belt.
One is a 2.5 hp Lifan 97cc similar to the Tecumseh you found. I use a Max Torque V-Pulley clutch to a whizzer sheave but the gearing is a bit too tall so I'm going to change it soon to driving a rim to rim wheel pulley like I use on my Rocky Mountain RM7. 53 mph isn't necessary on an MB & this change should get me back down in the 40's max but increase the mid range & off the line acceleration.
-lowracer-

puretexan2 · Jan 22, 2011

Thanks guys. I'm curious ....when you add up the expensive parts to build one of these , how do you not have a reality check and figure you could build a small motorcycle with a Honda 110 that would be way cheaper and perform lots better. I keep getting slapped in the back of my head with that reality. Am I missing something? I know this may be the wrong place to ask, but I keep looking at my new lifan 110cc motor sitting there that cost less than one of the $200 belt /pulley setups.

lowracer · Jan 22, 2011

My newest MB didnt cost that much in money (just time).
New Lifan engine = $90
Max torque clutch= $50
V-belt =$15
Whizzer sheave =$40
Metal, Nuts & Bolts ~$40
If you already have the bike, the rest is fairly inexpensive & fun figuring things out while tinkering with it. I also think that as long as you keep it under 50cc's & 30 mph & still able to pedal, it becomes a legal power assisted bicycle & not considered a moped/motorcycle that avoids license, registration, & insurance in most States...
-lowracer-

Build-a-beast workshop · Jan 22, 2011

yeah....personally i think its ridiculous to spend over 500 on a bicycle... with a motor...especially if it ONLY has one speed. i bought my daily driver for 500, its a 2000, not some clunking heap from '86. but i guess if you want it all at once, and wanna be able to mount the motor and build it on your kitchen counter in an hour, 400-500 aint bad. (lord did i just say 400-500 isn't bad?im getting soft...wayy to soft)

Goldy · Jan 22, 2011

I like to keep costs down whenever possible, but in reality for me, it's not about how much it cost, it's about the satisfaction of doing it yourself...not to sound sour grapes, but you don't get much in the way of bragging rights by bolting in a kit.

puretexan2 · Jan 22, 2011

Ok yall convinced me. I was looking for something good to use to convince my wife, when I start spending money. I will have a clear conscience now. I can probably throw something together that will run...maybe

curtisfox · Jan 22, 2011

How about through one together,build one for your wife. By then you will be ready for a good build for yourself?...........Curt

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