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Picture of how to make the cheapest motorbike ever!
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 I have started makeing this instructable since I cant find anything nice on how to make a cheap motor bike. so here it is (my cost was ONLY $30) but i already had the motor and some other stuff. you will need to read through this whole instructable before you start also this is my second instructable so i may have forgoten something so just leave a comment. you should reach speeds up to 30mph depending on weight and ratio and the size of the engine.
  you will also want to check your local laws to make sure it is legal! and stuff
 
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Step 1: Materials!

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in this project you will need,
1. a bike of any size
2. a weed eater motor ( I used a 25cc craftsman)3. angle aluminum (hardware store)
4. a 6" long 5/8" threaded bar with 2 matching nuts5. a bike peg

Step 2: Prepare the motor

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it is better if the motor you are using doesn't have a clutch if it does then remove it. now take off all the plastic on the motor that doesn't need to be there mainly just over the flywheel. then if your motor doesn't have a clutch remove the cover over the crank shaft, not the crank case! it will take lots of effort, it helps to use a hammer. then take your bike peg and see if it fits the threading if it does your lucky, if it doesn't take the cover to a machine shop and have it threaded to fit the peg this is what i had to do

Step 3: Prepare the bike

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get the bolt and mount it to the brake cross section with two u bolts you will not have use of the rear brake on this bike so be carefull

Step 4: Mount the motor

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you are going to want to mount the motor on a piece of angle aluminum and a tension spring to keep it on the tire i am pretty sure you can figure it out based on the photos but if not just comment.
amalik2210 months ago

My bike does not have a rear brake assembly at all. I took it off some time ago as it was rusted and beyond use. How can I use throttle then?

worked fine for me

DakotaA13 months ago

are you suppose to take the clutch off cause every vedio i watched they say to take the clutch off.And some say to use a clutch

I tried to use a weedwacker clutch and it ware out after a few days. Not worth the trouble

ChaslasherH1 month ago

hi i am trying to make this and was curious what brand is the motor you use

brads42 months ago

brads4. u can email me at hugobrad25@gmail.com. or call me at 580-280-5411. facebook has made my account temporarily unavailable. wonder whats up with that!!!!

brads42 months ago

i can't believe u took off the clutch when u could have welded the footpeg to the clutch drum eliminating the need for a tensioner. also the engine l bracket could have been bolted to the seat seat post other than that u did ok. i had a schwinn (sp) english racer when i was 11. i bolted an 80cc westbend 2 stroke to it and direct drove an 8 tooth sprocket to a 40 tooth i had brazed to the rear wheel spokes. u do the math. i was doing about 120 when i eased by the 1st baptist on US 183 in snyder, ok. the nightwatchmen was drunk and asleep at the wheel of his wagon. seems to me that jess dunn and i lifted two motors from a warehouse on s. najavoe in altus. he took the clinton 50cc. jess was not too damn bright.

i would pay you to build me one

jwatkins910 months ago
I just got a weed eater just for this, the front brake is an issue, i have the scars to show not to use it without the back brake, my front brake is broken so i am connecting the clutch on mine to it so i don't have ti shut off the engine to stop.

Great job though!
--JWat

how long of angle iron

Jojocircles2 years ago
Could you explain how to take the motor out of the weed eater? my father and I are gonna try to do this project thanx!
you just basically unscrew and unbolt everything until you have just the engine
cshwenie1 year ago
Hey BIGHAIRYDUDE, I have a question. My dad and I built one of these but we used a turnbuckle for the tension. When I apply a very small amount of pressure to the tire, the engine sounds like it is bogging and can't push. But when I take a tiny bit of tension off, it works fine except there is not enough tension to keep the peg from slipping on the tire. Can you help?
celliott961 year ago
Hey, I have almost the exact same engine as you. Craftsman 25cc. Anyways, when I was trying to mount the angled aluminum beam onto the engine, the flywheel is in the way of the beam. Should I cut the beam so it doesn't touch the flywheel or should I just try to mount the beam somewhere else on the engine?
Jojocircles2 years ago
Can someone help me
Jojocircles2 years ago
Is the threaded twisty bar thingy needed? Btw Great invention
chiefs5433 years ago
How do you put the peg on the clutch shaft? Can you u just thread it with a tap and die? Would it work if you just mounted the clutch shaft against the wheel without the peg on it? Also, does it have to be adjustable tension or cant the engine be mounted firmly against the wheel?
BIGHAIRYDUDE (author)  chiefs5433 years ago
you can thread it yes it will not work shaft against the wheel but it would work if you used the clutch bell if you dont know what im talkin about it doesn't matter, and the engine can be mounted firm or adjustable its all preference
Thanks. This helped a lot
tobychan3 years ago
That's awesome! I have a 49cc strimmer engine I've been wondering what to power. Mine has a centrifugal clutch so I think i'll keep that on. But i'll let you know how I get on with it and post an Instructable, giving all the credit for the idea to you of course. :D
You2133 years ago
It seems like the motor would be floppy and stuff becasue there is nothing really holding it on... How stable is it?
BIGHAIRYDUDE (author)  You2133 years ago
holds very well with steel the aluminum bends but it holds up good i go over bumps hills and everything and it doesn't complain
I have a quick question for anyone that wants to answer. When you stop at a stop sign do you have to turn off the engine or can u just use your brakes?
BIGHAIRYDUDE (author)  phynicfirebird3 years ago
in this you have to stop the engine
Kiteman4 years ago
He's increasing the power, and restricting himself to front brakes only...

Anybody want to start a book on how long before he face-plants at speed?

Agreed, Its a great concept, but losing your back breaks and using only the front ones is a recipe for disaster. I have had a few nasty knocks because of my front breaks. I finally just ripped them off my bike
lol, face-plant, because it's a weed eater
BIGHAIRYDUDE (author)  Kiteman4 years ago
ha front brake kind of sucks so the real danger is not being able to stop quick enough
rimar20004 years ago
Very good work, BIGHAIRYDUDE, congratulations.

Beware of the front brake, it can throw you over the bike. I say this for own experience! That fly is funny but dangerous.
BIGHAIRYDUDE (author)  rimar20004 years ago
hey some of you guys might notice this is a copy of my original bike but for some reason that instructable deleted itself so i still had the pdf so i copied it over so its really the same bike as before