Instructables

How to power your bike with a whippersnipper motor

Contest Winner
This Instructable will show you how to modify your push bike with a small motor so you wont have to pedal as much and look a whole load cooler! I made mine using a really old kawasaki whipper snipper (weed whacker for you Americans) motor. I could get about 40kmh along a flat with no pedalling and an easy 55kmh down a slight slope, I could go faster than traffic!

this is intended for the Instructables Bike Month of May contest, so please vote, I would really like to get a t-shirt. they are cool.

I'm not responsible if you hurt yourself/others/things/stuff in anyway. Also if you make something that is illegal and get caught don't come running to me, its up to you to check the regulations in your area for motorised pushbike.

This is also my 2nd Instructable so please be constructive and supportive.
 
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Step 1: Stuff you need

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I made this bike modification with few tools, materials. You just need to think about what you doing and what you want to achieve.

you will need:

  • a bike (any will do, but the simpler is best ie. no rear shocks and stuff because it just complicates things, although still possible)
  • a motor of some kind, preferably small but with a fair bit of power, a clutch is nice because you can ride it normally without the motor on, although still possible without. and if it has mounting holes or something that will make it easy to strap on your bike. I used a small 2 stroke whipper snipper motor made by kawasaki, bit gutless as I'm 85kgs but I had a bigger carburettor on it before when I was mucking around with it.
  • a bit of thick plate to use as the mounting plate/bracket. thick stuff is good because it hold your motor nice a steady.
  • a roller/driver shaft to run on the back wheel to transfer power to the wheel. size is important as it affects gearing and therefore final speed. I did the math and figured out it needed to be bout an 25mm - 40mm in diameter to get around 40-50kmh
  • welder
  • grinder
  • miscellaneous, tooling, ie screwdrivers, spanners, persuasion tools (big hammer and shifting spanner)
  • an oxy-acetalyne set is nice to bend your plate if it needs it
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MrSlehofer. made it!3 days ago

I built it but without friction drive but with direct drive.

I even have video of it on youtube :D

enjoy :D

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JesseR111 days ago

Do you sale the clutch roller thing?

josephl213 days ago
Wareagle3 years ago
I am building one of these, but i ran into a problem. how do you keep the bike peg from unthreading itself when its on the bike?
Dowaine Wareagle6 months ago

if its going the right way it will tighten itself

thats how it is on minethat i built

Jaycub Wareagle3 years ago
You could put some JB weld on the threads.
tonroh171 year ago
i made one with a 1300 cc harley engine and i died
tonroh171 year ago
are u an aussie
mikamark2 years ago
is mounting the motor where you r putting it efficient? does it work as good as other ways? will it last without breaking? and for how long?
thx help will be appreciated :) :)
will this work with a lawnmower motor?
Althought this is an old post, it is for anyone else considering the same thing.

In short, no. Because motors used in "most" ( I say most because i have not seen every single lawn mower in the world) run direct- drive to the rotating blade.

The blade is spinning on the wrong axis, and although some simple gearing may solve this issue, i do not recommend it without proffesional machinery.

Basically, the lawn mower's carb is set 'sideways' (in comparison to the direciton of driver) , and because "most" lawn mower use float carbs, it will not work if you flip it to over to drive your wheels.

Did that make any sense?

Country Dude's idea may work but it seems sort of like a lop-sided baseball pitching machine...
First of all great comment! And it was wise of you to say "most". There are some Honda push-mowers with blade clutches and heavy flywheels so you can turn off the blade on back on again whenever you want. (without turning off the engine)
This past weekend I was looking at a rear drive self propelled lawn mower thinking "I cna make this work!" The main shaft has a belt wheel mounted on it, belt connects to the back of the mower to the gearbox by the rear wheel. All mechanical parts are there, would just need to be re-worked for the bike.
You can if it is a 2 stroke but the problem is some carby's only work at one angle, so the fun part is trying to rotate it so it works with the motor running a horizontal axis.
all you hafto do is put a rubber disk on the shaft and mount it so the rubber disks are on the left or right side of the wheel (dependent on which way the engine rotates) and use a spring to apply pressure horizontaly not vertically
no
Lemon1022 years ago
Would this work better on a mountain bike with gears?

Cheers,
Lemon
Bosun Rick3 years ago
Just a dumb question here; Why did either of you just adapt a chain drive from the motor down to the stock bicycle chain? You would get much better speed, choices of gearing (depending on the bike's sprocket set), and less tire wear! An adjustable idler sprocket would keep the chain tightened (add a weight & it could become self adjusting). Nice Instructable, but these might be hints for a "New & Improved" version.
I thought of that to but then i realized that the pedals would be spinning at like a zillion miles an hour.
ross bicycles used to make a ten speed that had a freewheel clutch in the front cranks. it was so you could shift while not pedaling. if you could find one of them, they would let you hook an engine up and still use the shifters. i put a 3hp briggs engine on one when i was a kid in the '80's. i could get that 10 speed going faster than i really wanted to go, wanting to live and all.
If you run it on a chain drive, you can take the pedal drive parts out of the project.
BosunRick - this idea is intriguing to me... do I understand it correctly in that the chain path would then be triangle shaped?

I'm not knocking your idea at all, in fact I like it very much, I'm just hashing it out. So... My understanding of bike gearing is basic, but it seems that if the chain traveled under the rear sprocket and then straight up to the engine, there might not be enough chain contact with the rear sprocket. Hmm...

Also, if the chain traveling at a down angle, from the engine to the front derailleur, it might interfere with the front derailleur operation.

But I suppose the motor could be mounted inside the frame instead of over the back tire... I guess that's what motorcycles do... Wow... this changes everything in my plan! Great suggestion!

too much work for that i was going to try that when i did mine but getting to align right was to much work for most diters so friction is easier
alterator3 years ago
nice build, but I would have made direct drive.. roller thing replace with a sprocket, chain longer and threaded through everything. to join motor rear wheel and pedals.
duh-man4 years ago
CTGee duh-man3 years ago
No. It is a Whipper Snipper.
11richie213 years ago
do all gas motors spin the same direction? I have a gas motor from a leaf blower but i dont know which side of the bike i should mount it on
Lol no they don't just start it up and see which way it spins. There's nothing worse than only being able to go in reverse so make sure you check your actual motor ;P
DanteDante3 years ago
This is ridiculously awesome. Good Instructable!

I'm in the early stages of building one of these right now. Unfortunately, I don't have a welder (yet), so the process of finding just the right parts to mount the motor is taking longer than I'd hoped. I think I'd like to incorporate the engine kill switch... you know, because it's there... So why not?

I also like the idea of using spring tension to hold the drive shaft against the tire... but I wonder: would there be much benefit to having an additional wire cable running from the rear brake lever so that, when squeezed, it would simultaneously apply the rear brake, and also pivot the motor & drive shaft slightly off the tire?

Anyway, I have 5 old bikes and 3 old motors to work with, so I'm sure I can cobble something indescribably unsafe together pretty soon.
now i just gotta find a weed wacker...
mista.v3 years ago
What about a killswitch or some kind of clutch to disengage?
b-train (author)  mista.v3 years ago
Theres an ignition killswitch on the front of the engine near the pull start, and it has a centrifugal clutch built in.
KiW4 years ago
WOW, thats just cool, I wanna have it too, but then you got the problem... cops... law... here in holland they dont allow your to drive on cool stuf only borring things are allowed here... damn still gonna do it with a cycle I have left some hwere in the middle of no where. thanks dude looks cool!
frixx5 years ago
what is a whippersnipper motor? my translator wont translate it plz help thx
dmitri11 frixx4 years ago
weed whacker, weed trimmer, weed eater, same thing
there is also weed strimmer
duh-man frixx4 years ago
a weed wacker motor
lukeyj15 frixx5 years ago
<a rel="nofollow" href="http://www.melbournesmowercentre.com.au/images/Category/38.jpeg">http://www.melbournesmowercentre.com.au/images/Category/38.jpeg</a><br/>The above link/address will show you what it is<br/>
b-train (author)  frixx5 years ago
haha its a motor that powers a whippersnipper. a whipper snipper is also know as a weed wacker, its a motor with a long driveshaft pole and a rotating wire/cord on the bottom which spins n cuts grass
In fact that is a great performance. keep it up. but please could you explain to me the mechanism involved . how the motor is able to power the bicycle wise_coleman@yahoo.com
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