Build an Electric Motorcycle on a Budget


Introduction: Build an Electric Motorcycle on a Budget

About: Maker of things. Small business builder. Follow my latest project on Twitter @joe_murphy

The Goal of this project was to convert a classic motorcycle into a clean, quiet, electric daily driver that would reduce the amount of automobile pollution caused by my short to mid-range driving trips.

COST: $1,000
RANGE: 40 Miles
SPEED: 40mph with current sprocket setup
CURB WEIGHT: 320ish Pounds, around 50 more than original
RECHARGE COST: Less then a Penny per mile

Ahhh yes, The Electric Dream! Clean, Quiet, and best of all not a drop of Gas!

There is a lot of great information on current Electric Motorcycle Instructables, but I still ran into some snags and made some mistakes along the way. So I will do my best to cover where I went wrong to save you some time, money, and effort. When the build was over a book called Build your own Electric Motorcycle was published, Needed less to say its a resource I wish I had along the way.

Also, by no means am I an expert. In fact, the only class I failed in college was "introduction to electronics" . In saying that, I am looking forward to any comments or feedback on how to improve my project. Also follow me on Twitter or on my Electric Motorcycle Blog to  keep up with my current projects and Electric Motorcycle News.

Step 1: What You Need

Here is a list of what you will need and how to find it:

A Plan: This is the best question to ask yourself before going out and buying anything.
How far, how fast, how much? To get a good idea of this, spend some time on: - its got 1000's of Electric Motorcycle conversions with pictures of the bikes and the components used to make them.

1.Donor Motorcycle or a rolling chassis - Check Ebay and Craigslist. Personally, I like to set up an RSS feed from my craigslist search, otherwise I browse for way to long when my ADD kicks in. I found my 1967 Honda Dream(ca160) on craigslist for $275, with frozen motor, but hey, I don't need that anyway.

2. Electric motor - There are lots of options out there, but I recommend a Brushed 48v Etek Briggs and Stration due to its price, power, and availability on eBay. The original is no longer in production so your options are to buy a used motor or get a clone. Also, if you have a local golf shop go talk to someone there - they are gear-heads too! These guys will like you and they will like your project. So see if they can cut you a deal on an electric motor, there will be plenty of just sitting around.

3. Batteries again, consult your plan. My plan was 30+ range, so I picked up some deep cycle batteries at walmart for $62 a piece. They are 12v 105 aH. Looking back, I wish I would have gone with some smaller and lighter batteries. I really don't need the amount of range these current deep cycle batteries provide.

4. A motor controller that delivers/regulates the energy from the battery to the motor. Think of this as a transmission. I found a Curtis 48volt 300 amp controller on eBay for $150.

5. A twist grip throttle that sends an electric signal to the controller - which determines how much energy is sent to the motor from the batteries. Most popular is the Magura Twist grip, available on ebay.

6. A battery charger to re-charge your batteries for continual (cyclic) use. I am still working on finding the best charger for my ride, but I would like to do something that could be out on board.

7. A high-current switch or Contact Buy this on eBay or at a Golf Cart shop. This part makes the loud "click" sound when your turn on a golf cart.

8. A high-current fuse to limit the amount of energy drawn from the batteries in case of a short/failure. Typically = to Control max amperage. I got a 2 300amp fuses on eBay for $19 bucks

9. A large gear ratio to reduce the amount of current required when accelerating (this can be accomplished with a large custom rear sprocket and a small front gear/pinion on the motor). My current gear ratio is 3:1, optimal would be 4:1+

Optional stuff: instrumentation, speedo, ammeter, or a way to judge batteries state of charge.

Step 2: Frame Modifications

Its time to make sure the Doner Bike is road ready. My bike also had a lot of rust and some body work that needed to be done.

Remove Rust:

Paint Bike:

With any old bike its a must to check front and rear suspension, barrings, and brakes. Check out Dan's Motorcycle repair guide to address any issues.

Time to put together some way to mount your batteries. Your best bet here is to create cardboard cutouts the sames size as your batteries, and then see what configuration will work best. Cuts done on moving around large heavy batteries. I was able to use some some 1 inch steel from lowes and come up with some pretty steady battery mounts. Remember to keep the battery weight as center and low as possible to help with handling.

Step 3: Assembly

Mount the motor:

1) Use the same location as the gas engine using as much of the original frame and existing engine mount as possible. I was able to use 2 of the existing motor mounts, and then added a 1/4 inch 4x8in piece of steal, which is bolted and welded to the frame.

2) Mount the motor on the rear swing-arm. Check out for some ideas. Here is an example of a swing-arm mounted motor:

Controller, Main Contact, and Throttle:

Its is very important to mount a controller in a place that is going to get a lot of air flow, because these things can overheat and fry if your not careful. Curtis website has some really helpful information on how to mount and wire these controllers, this is a huge resource that most of the controller manufacturer offer so find yours and use it. I was able to mount on the side of the frame where the tool kit used to be. This provides easy access and lots of crisp cool airflow. The main contact was mounted on the inside of the frame, close to the batteries and controller. Below is a detail wiring guide, this is probably the most important part of this instructable and the part that gave me the most problems during the build. The main contact should be mounted in a place that is easy to get to. I put my inside the body of the frame, this was a mistake. Hard to get my big hands in there and I can never see whats going on when I am moving wires around.

Throttle should have 3 wire red/blue, brown, and black. You will need to use a multimeter to test which leads give you 0-5k ohms or resistance, these wil be connected to the controller. In my project these where the brown and red wires. Then the black wire need to be connected to battery negative or negative terminal on the main contact.

Batteries should be wired in series this means positive on battery 1 to negative on battery 2 and so on... look at the picture, I'm told its worth a thousand words.

Step 4: Troubleshooting and Issues

If you get it all together

Verify that battery (-) connects to the B- terminal of the controller. Connect
voltmeter (-) lead to this point.

Connect voltmeter (+) to the battery side of the main contactor. Check for
full battery voltage. If it is not there, the trouble is in the battery pack, the
cables to it, or the power fuse.

Connect the voltmeter (+) lead to the controller B+ terminal. You should
read a voltage 1 to 5 volts less than the full battery voltage. If this voltage is
zero or close to zero, the trouble is either a bad controller, a bad 250 & resistor
across the contactor, or an incorrectly connected cable between the contactor
and the controller. Trace the cable to make sure it is hooked up right.
Remove and test the 250 & resistor with an ohmmeter. If these check out,
the controller is malfunctioning. If you see full battery voltage at this point,
then the contactor has welded and must be replaced.

TEST 2 Check for main contactor operation and KSI

Turn the key on, place the forward/reverse switch in forward or reverse, and
apply the throttle until its microswitch operates. (In these procedures, we
assume the throttle is equipped with the recommended microswitch.)

This should cause the main contactor to operate with an audible click.
Connect the voltmeter across the contactor coil terminals. You should see
full battery voltage (minus the polarity diode drop).

The controller KSI terminal should also be getting full battery voltage.
Verify this by connecting the voltmeter (-) to the controllers B- terminal,
and the voltmeter (+) to the controllers KSI terminal.

If the contactor and KSI terminal are not getting voltage, thats the problem.
Use the voltmeter to nd out where it is not getting through. Connect the
voltmeter (-) to the controllers B- terminal and check the following points
with the voltmeter (+) lead to trace the ow:
Curtis PMC 1209B/1221B/1221C/1231C Manual 31
1. First, check both sides of the control wiring fuse.
2. Check both sides of the polarity protection diode to make
sure its polarity is correct.
3. Check both sides of the keyswitch.
3. Check both sides of the throttle microswitch.

If the contactor coil and KSI are getting voltage, make sure the contactor is
really working by connecting the voltmeter across its contacts (the big
terminals). There should be no measurable voltage drop. If you see a drop,
the contactor is defective. (We assume the recommended precharge resistor
is in place.)

TEST 3 Check the potbox circuitry
The following procedure applies to the standard throttle input conguration for
these controllers, which is a nominal 5k& pot connected as a two-wire rheostat (0
= full off, 5 k& = full on), and also to 5k&0 congurations. If your installation
uses a controller with a throttle input other than 05k& or 5k&0, nd out what
its range is and use a procedure comparable to the one below to make sure your
throttle is working correctly.

With the keyswitch off, pull off the connectors going to the throttle input
of the controller. Connect an ohmmeter to the two wires going to the
throttle and measure the resistance as you apply and release the throttle. The
resistance at the limits should be within these ranges:
RESISTANCE (in ohms)
05k& POT 5k&0 POT
Zero throttle: 0  50 4500  5500
Full throttle: 4500  5500 0  50

If these resistances are wrong, it is because the pot itself is faulty, the wires
to the pot are broken, or the throttle and its linkage are not moving the
potbox lever through its proper travel. Apply the throttle and verify that the
potbox lever moves from contacting the zero-throttle stop to nearly contact-
ing the full-throttle stop. If the mechanical operation looks okay, replace the

hope this all helps leave a comment if you got something to say, and for more infomation check out my website on electric motorcycles



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    85 Discussions


    7 months ago

    Well done. As a motorcycle enthusiast, when I get a chance to build one, I will be coming here to check this out again.

    Just today I began thinking about converting my old 1964 Honda Sportscub 49cc bike to electric since it hasn't run in over 25 years.

    Inspired by this article. Ty

    1 reply

    Cool! I'm happy to know people are still finding it useful. Good luck!

    So I think I found the same batteries at Walmart, but they don't have a milli Amp-hour (mAh) rating on them. Instead, they say 625 MCA 9Marine Cranking Amps). Is this the same battery, and how do these relate to each other?


    1 reply

    No, they're not. There are two general type of these batteries, one is design to produce a lot of current for a short amount of time, like to start a car or boat engine. This is the type you describe with their capability measured in Cold Cranking Amps. The second type is a deep cycle battery and this is what you need. A deep cycle battery is designed to produce a low amount of current for a long time, like running an electric motor as we are doing here. You will want deep cycle batteries, ask for ones intended to run a trolling motor.


    4 years ago

    Great project

    For anyone interested: I'm currently restoring a 64 Honda Benly 150, which I believe is the exact bike seen here. I have a spare parts bike with everything except a motor that would be perfect for this project. If anyone is interested I'm looking to sell. Let me know.

     At the time of the photo I was only using a foot brake...I know scary and dangerous.

    The front brake handle is on the left (visible in the first picture). On a motorcycle, the rear brake is actuated by a foot pedal, as the other hand control is the clutch (the brake would generally be on the right on a motorcycle, so he must have moved it).

    It's a geared bike- the front brake is on the right handlebar (step 3 image 4) and the rear brake is the right foot pedal (step 2 image 1).  The clutch is missing because it's unnecessary for a single-gear electric bike.

    I see you are pro indeed :) thx
    anyway, this  is realy great bike ,pity no one is selling proper parts in this backwater country of mine ( i had only made a bicycle with electric hub motor - nothing special this days )

    Wonderful. Did you know that bike is pretty valuable in one piece? With that much battery, time to go three wheels, no?

    Not wanting to be naughty, but why do you need a system to "break" it? I'd just run it into a tree or something.
    If I wanted to slow down or stop I would think about putting "brakes" on it.
    LOL now have fun with that!

    Shorting the moroe terminals will cause the motor to generate power, and then eat the power in reverse- meaning, it will resist any movment and convert it into heat. Using PWM, you can vary the strength of this effect, and voila! you have breaks!