The story of how the electric bicycle was born


Build it Now!
I wrote a short writeup for anyone willing to make or build upon this design. You can visit the project page by clicking HERE.

Circa 2008. At age 13 my adolescent mind desired a motorized bicycle. With absolutely no budget, I began brainstorming ways to cannibalize my seldom-used Razor E300 electric scooter with its rusty bearings and dry SLA batteries… This is the short story about how my DIY e-bike came to be.

A very early progress photo indicating the start of the project.
A very early progress photo indicating the start of the project in ’08. (Gutted Razor E300 – Green)

After some trial and error with some early ideas, and just as I was about to push the project aside for the upcoming school year, I came up with an Idea that uses two very simple U-bolts and structurally nothing else.

Budding the mounting flange of the 24vdc motor to the front fork of my Trek 4300 (and later the 4-Series) I took some measurements and persuaded my father to buy me two 1.5 inch U-bolts for a few dollars from the local hardware store.

Some minor filing was needed on one of the bolts to get it to fit where I wanted it, but once I got the motor mounted to the front fork of the bike, and had the suspension locked (properly with dedicated switch), I had to find a way to deliver its output to the front wheel. For this, I found that a basic skateboard wheel (sans bearings) epoxied to the motor’s original sprocket and nut would work just fine. I later replaced this with a proper motor arbor after I found the epoxy beginning to wear out. I also found that some all-weather grip-tape applied to this drive wheel gave it much more needed traction in wet weather.


The SLA batteries and motor controller were stored in a canvas tool bag atop a pre-existing carrier rack. On larger bikes, like my later Trek 4-Series, this “tool bag” can be strapped to a modified (simply bent open) cup holder in the center of the frame. The scooter’s throttle handle follows a standard diameter and easily clamps on between the shifter and right handle grip of the bike.


This was the setup I drove for a couple years before I out-grew my bike. No worries though, I found that this system is easily transferable to most other Trek Bycicles (and possibly other brands as well) after I got my Trek 4-Series. It only takes four nuts, a small tie-down strap, and one zip-tie for anyone to remove or transfer this system to another bike.


On a full charge, with two 12v 10Ah SLA batteries (a bit larger then the scooter’s original 7Ah set), this motorized bike will pull you along at 20mph (32.2Kph) for 10 miles (16.1Km) seldom-assisted (I.e. only helping it when accelerating from stops). It certainly adds loads of fun to an otherwise normal bike ride.

To this day I have not found a better diy electric bicycle conversion with all the benefits of this one. It doesn’t damage or alter the bike itself in any way, it’s easily removed or transferred to other bikes, and it costs virtually nothing compared to the commercial kits and hub motors.


70 thoughts on “The story of how the electric bicycle was born”

    1. I’m not sure of the exact motor shaft specs off hand, but some Googling tells me that the shaft is probably 10mm in diameter (easily filed down to 3/8inch) and about an inch long. The motor arbor adapter (a thing commonly used for mounting polishing wheels on bench grinders) that I used was considerably oversized, at about 5/8″, but I managed to hack in some spacers to get the thing to turn symmetrically.

      1. I’ve posted a link to an 8mm adjustable / flexible arbour for a standard e300 8mm motor spindle if anyone’s interested.

        Could be a deal breaker if you can’t fix your skateboard wheel on properly. Happy electric biking!

        1. That is an 8mm to 8mm female coupler commonly used for NEMA stepper motors and lead screws (I have a couple on my 3D printer). Unless you plan to use that coupler as the drive wheel itself, I don’t see how that would work as an arbor. It’s less then half the diameter of a skateboard wheel too

          The easiest arbors to come by on eBay are 1/2 inch motor arbor extenders (used commonly for bench grinders). With these however, you will either need to find or hack together a collar/spacer that will fill the gap between the 1/2 inch arbor and 8mm motor shaft. This is what I did, and I think I even used the sprocket spacer that the motor came with after cutting it in half.

    2. how waterproof will this be? i’m thinking about building this for my racing bike to shorten my way to campus (its about 30 km on a dailybasis ant it really ain’t the way i wanna start my day) but i think it will be useless if the motor isn’t waterproof, because its raining here very often.

      1. A few regular freshwater puddles shouldn’t hurt anything. The electronics (controller/throttle) I’ve come across are sealed and/or conformal coated. Most scooter motors will come with sealed bearings too. The one problem you may face is finding a suitable drive wheel option for perpetually wet weather. The skateboard wheel I use is wrapped in industrial outdoor grip/grit tape (usually used for boats and pool decks); This is because the smooth rubber wheel would otherwise loose traction if it drives through anything more then a brief puddle. Perhaps more pressure on the drive wheel would be required in your case.

  1. This thing is amazing buddy. I am working on one myself (following your instructions 🙂 )for my father in law to help on an adult trike. I have one question, does your model have an electric brake unit connected in the mix? I am concerned if I just straight use the normal bike brake will it cause any drag on the motor to eventually cause it to fail or is this a non-issue and just works? Sorry for my lack of knowledge I am not an electrician or very savvy with this stuff and just don’t want this to fail on him once I get him the bike.

    Thanks again,


    1. Thanks! There was an E-stop switch installed on the original scooter’s brake handle, but all it did was prevent the user from “riding the brakes” as it is called. Both the scooter and my bike still rely solely on mechanical braking. I have omitted this E-stop from the motor-controller circuit many years ago with no ill effects on the electronics (Everything but the batteries are still original!). There is also no perceivable change in friction while coasting when the motor is physically disconnected from the circuit compared to when it is in circuit; in both scenarios, the bike will come to a stop at roughly the same distance. As long as you avoid holding the brakes and throttle at the same time, as with any vehicle, you should be golden. Also keep in mind that this is a peddle-assisted design, meaning you should always help out the motor, controller, and batteries when you are accelerating by peddling as you would normally.

      1. Fantastic! I almost have all the parts and am so excited to build it. Once completed I will be doing another to connect it to a Fat bike that I will use to take down the trails to the beach.

        I will send you some pics :)!

        Thanks again!


    1. That motor is a 36volt motor. The mounting bracket looks the same, but you would need to get a 36volt controller with throttle handle to go with it. (As with the one I mention below too, you might also need to drill out the mounting holes since they both seem to have built-in threads; not a problem.)

      I would recommend this motor by Razor (it’s what I use):
      It’s a 24volt, 300watt (12.5amps) motor. Yours is a 36volt, 300watt (8amps) motor. Both output roughly the same amount of power, but a 24volt system should be cheaper since it doesn’t need as many batteries.

      With this 24v motor, I would also recommend this 24v controller; also comes with throttle handle (I use this as well):

      This, along with a little ingenuity, should get you up and running in no time.

    1. I remember it was pretty stuck on there when I had mine. It may be reverse thread too, but I can’t remember; look closely to find out. You’ll need an appropriate way to grip both the nut and the sprocket/shaft (the sprocket is keyed to the shaft and will slide off once the nut is free). Try using some Vise-Grips, a small hammer, and perhaps some penetrating oil (WD-40 or Liquid Wrench) if you have a particularly old and crusty motor.

      1. my e300 razor scooter has a reverse thread on the motor shaft, so be aware that you might be tightening (counter clockwise) when you think you are loosening. Try clockwise on the nut instead.

  2. Hi Mike, great design. I have old roller skate wheels. Any idea how I can remove the bearings so I can use the wheel for my friction drive?

    Also, I have an old razor 24 volt 375 watt motor but no controller. The motor seems to run fine without the controller. Can I avoid using a controller and just use two heavy duty switches where I can apply 12 volts with the first switch and then up it to 24 volts with the second switch? If I use a controller how do I bench test the motor as most of these Razor motors need the vehicle moving forward before the motor will kick in?




    1. Thanks. To remove roller skate bearings, you’ll need a hammer, and a screwdriver. IF you want to keep the bearings for another project, DO NOT strike the area between the raceways (it’s the place where the ball bearings are held), instead, only strike the outer or inner rings/raceways of the bearings if at all possible.

      If you have a heavy duty enough switch, and a safe way to toggle it, using it to control your 24v motor without a controller should work fine. I’d put in a 15A-20A bi-metal circuit breaker in-line just to be safe (most scooters come with one). A permanent volt meter might be handy too.
      Also, I have no experience bench testing those “smart” scooter controllers.

  3. Hey there!

    Thanks for the helpful information.

    Just curious, what is the range of this setup? How many miles can you go before the battery runs out? What speeds (unassisted) can you reach?

    Also, what battery (or batteries) are you using?

    Thank you!

    1. The batteries I use are two 12v 10Ah in series, though I’m thinking about upgrading to a few LiPo packs in the future. Seldom assisted (only pedaling during acceleration), I got 10Mile range at 20MPh tops. This however depends on your drive wheel, front tire, (think gear ratios) and rider sizes.

  4. Thanks Mike for the feedback on the controller. If I have a 24 volt controller (origin unknown could I use it with my 375 watt Razor PM motor? Not sure how to figure out the wiring.

    I heard that one can get dead laptop lithium ion batteries and resurrect them into a working bank again for an ebike, create your own light weight high capacity 24 volt bank. Thoughts?


  5. Hi, Nice job on the project! I want to build one on my own and am confused by how you connected the battery and the motor. Did you buy any wiring harness? Thanks!

    1. The battery and the motor both connect to a standard Razor E300 speed controller (also called a motor controller). It receives a signal from a twist-throttle handle and allows the user to precisely control the speed of the motor. My motor, controller, and throttle handle were all salvaged from the same scooter. You can buy “replacement” ones pretty cheaply too.

  6. Mike I went to Granger Products and saw numerous motor arbors in the 3/8 ” range with different lengths. Can you help spec me a arbor? I have a Razor 375 watt motor and a roller skate wheel that I guess is about 2 inches thick.



  7. Hi Mike Interesting stuff!
    There are no freewheel. How much resistance can you feel when only pedaling?
    Is it notable?


  8. Mike can you provide greater specs on the motor arbor? How long does it need to be? Where did you get it? Part number?



    1. The throttle handle’s mounting dimensions follow an international standard for most bicycle and scooter handlebars; 7/8in or 22.2mm. It locks on like any other handlebar accessory.

    1. Some bicycles have a “lockout” lever built into the front suspension fork to make riding on smooth or uphill surfaces easier and more efficient on the rider.

      1. My bike doesn’t look like it does that.
        BTW the window of space for the motor (just from eye’ing) doesn’t look big enough. (I’m using SCHWINN bike.)
        What do you think would be the best approach for these situations.

  9. I ‘m facing problems getting the right parts . As i live in india it is very hard getting the right batteries. But still i managed to get the 12 V 7 Ah batteries. Will they work with razor E300 motor you have mentioned? Please reply fast

  10. Hello,
    I am extremely fascinated by your setup for the friction drive! I was wondering what battery pack within a 30 dollar range would give me about 15+ miles because I am on a budget. Thank you so much! It would be amazing if you could get back to me!

    1. I use two 12V 10AH SLA Batteries from ChromeBattery. It looks like you can get a pair from Amazon for about $45 and free shipping (US). This is probably your cheapest and most reliable bet for the mileage. Your mileage depends on a number of factors as well from your all-up-weight, wheel sizes, battery size, and most importantly, your driving habits.

      There are some marginally cheaper SLA batteries available, but those generally are meant for security systems and battery backups; they are not suited for the high current draw of an electric bike and will likely overheat and quite literally melt.

  11. Hi mike. Great project! Im 14 and looking to do this project. But my brain could not function when I looked at the control module diagram. It was to complicated for me. It would really help if you could make a video on how to install all the wires and stuff and how to install the on and off button and specific wire name would help to please make one. Thanks!

    1. Awesome! Unfortunately I can not make a video of the process. It would be much too confusing and messy since I have like a mile of cheap electrical tape wrapped up in that project box.
      The wire names and colors are all dependent on the motor and motor controller you use anyway. Razor scooters also have a safety feature that only allows them to charge when the master power switch in in the off position; that is what the thinner wires are for in the diagram. It really should be as simple as connecting the dots, still, here is a simplified diagram for you:

      If you want, feel free to send us some pictures of your hardware and we’ll be happy to help.

  12. Thanks. Now that I look at it in detail im sure my dad can help me out. Thanks for everthing. And thanks for taking all the time to respond to every comment! You rock!

  13. Oh sorry forgot to mention. My real problem was conecting all the wires to gether. Not like plugging them into the wire but like on the diagram, right under the on off swich, will those wireis already be there and conneted? Or do I have to connect them. And if so how do I do that.

  14. Hi,great set up!
    I’m in the UK and would like to do something similar but the motor would have to be 250w Max to comply.
    Do you think an M Y1016 250w motor would work with pedal assist?
    Thanks in advance

  15. I have a couple old 12 v Ni-Cad drill batteries laying around, do you think these could work in this instance?

    Thinking about applying this setup to a cruiser I have. Was thinking about getting a second charger and converting it to a Battery socket over the rear wheel.

    Any suggestions would help.

    Also, excited to see what you do with Lithium Ion. Keep up the great work, this is the best conversion kit/example I have seen to date.

    1. Ni-Cad drill batteries are very good at delivering a lot of current, though depending on their size/capacity, their run time may be a little low. It’s worth a shot though. I’d also probably look for used drill chargers or drills to serve as the receptacles for the cruiser; it’ll save some pennies.

  16. Would you be able to build a battery for me like the one which you did in the video to fit the reduction kit – please let me know. thank you al.

    1. Unfortunately no, sorry. It’s really easy though, all you’ll need is two 12volt SLA scooter batteries connected in series to make one 24volt pack. You can Google it to find out more.

  17. Hi, your setup looks like a very accessible solution to building an e-bike.
    Do you have any thoughts on how to clamp the motor, so that when not in use can be lifted from the wheel.

    Many thanks for your designs and efforts.

    1. I do not know of any other more simple solutions then what you currently see in the here. Honestly though, you shouldn’t ever really need to disengage the motor form the wheel, it coasts just fine from my experience.

  18. amazing – hey I wanted to mod my tandem for burning man and thought this would be awesome but I’m not sure if the bike frame has enough clearance from the wheel, what you reckon?

    tandem bike pic


    1. Great idea! You might want to consider the back wheel for mounting options as well if the front has its limitations. You still might have to get creative and make a kind of wood or metal bracket that firmly positions your motor in just the right place.

  19. Hi Mike.

    How did you remove the sprocket from the motor? I messed up a motor by demagnetizing it when I opened it looking to pull the shaft out! But that was the only way I was able to take off the sprocket since the nut that held the sprocket stopped rotating with the shaft.

    How did you remove the nut and sprocket without opening the motor?
    Thanks in advance,

    1. Hi Steve. The sprocket is held on with a reverse threaded nut most of the time. (I.e. lefty tighty, righty loosey) The sprocket is also keyed to the shaft. This means you can grip the sprocket firmly with a vice or channel locks, then “loosen” the nut with a normal wrench by turning it to the right.

  20. Sorry Mike for not responding in 2015 on the Lipo bike page. I thought I had made a post (in Oct. 2015) and was waiting for an answer (which I wasn’t aware that you did give an answer!), but thought maybe there was a glitch in the system and that I didn’t make a post. Thanks for giving the hypothetical. I was thinking of using one of two Turnigy motors (D2836/8 1100KV Brushless Outrunner Motor, or NTM Prop Drive Series 35-42A 1250Kv 600W [I copied the text verbatim from hobbyking]). I live in the Bronx, NY and there are many inclines. I weigh about 185 and I want to be able to ride at least 70-80 minutes before needing to give the LiPo a charge.

    Two points that I want to ensure I cover:

    –I wouldn’t mind if I have to charge for an hour and be able to go 30-35 minutes on that charge.

    –I would be interested as to what batteries I would need to do that (I want to use a 24V system) with the two motors mentioned (or is your motor better?).

    Thanks in advance 2 times! and thanks for your response

    1. It might be. Every bike is different. You might want to consider adding an extra u-bolt on the suspension tube opposite from the motor to lock it artificially. Alternatively, another user in the comments managed to mount the motor on a rear luggage rack on the back wheel of his bike:

  21. i have been looking around for some hints on how to convert my bike to e bike for about a month now. I have been looking at these exact motors on ebay . my problem was mounting the motor and where. Thank you very much, what a simple idea! often the best ideas look simple in hindsight but i would never have thought of your solution. Thank you again for a great idea!
    cheers from Australia.

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