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Motorbike starter motor on a Scooter? Answered


I changed the starter motor on my bike some years ago, and this motor is laying around in my garage since then, working!
I always wanted to build an electric vehicle, and i would like to start with an electric scooter!

My questions are: 

1. Would the motor work and run on a scooter?
2. how much would the battery last? I plan to use a normal motorbike battery, i dont know much in electronics, they are 12V and 10-70Ah
3. will the motor heat up and burn?
4. what range would it have?

The motor in question is a Mitsuba, aftermarket mounted on my bike a Honda CR 250 if this helps.

Thanks in advance!


Hi dsirotic, Over the summer school break, my daughter and I finished this scooter project powered with a Honda starter motor. Added heat sinks cut down from a computer CPU heat sink. Cooling fan is mounted to the armature shaft on the brush side of the motor. Air blows over the motor housing. Max speed through a PWM controller and MOSFET transistors is 19 mph as shown on Android phone gps/speedometer app.

Again, most will say this won't work or you can only run the motor for a couple of minutes. Like the go kart, with a good Optima battery, you can run around the neighborhood for about 20 minutes. Longer of you are not full on the throttle.

Not the best way build an electric scooter, but all components are relatively inexpensive. The start motor (used) cost $20. The battery is the most expensive part, but you can still use it to jump start cars.


dsirotic - Did you ever make motorbike or other vehicle powered by a starter motor? I just reworked my e-cart over the summer for my teenage son. After re-reading your question again, I am not sure if a motorcycle/scooter starter motor is a good choice. Along with the electrics, you will have to consider the final drive gearing or gear ratio. I started with what is called a "gear reduction" starter motor. The internal gear box already provides a good starting ratio. From the output shaft I would attached a 10 or 11 tooth sprocket and then try to keep the final ratio in the range of 5:1 or 6:1 as starting point. Everything I did over 14 years ago goes against every precaution and fact indicating that is will not work. It is not very efficient, but everything is relatively inexpensive. The motor will get hot, but as it gets hot, it also will get slower, that is when I usually stop and keep the cooling fan. I have never experienced any type of thermal "run away" as to self destruct the internal motor parts. In fact, the armature and brushes are the originals. I periodically disassemble the motor and gear box to clean and re-lube everything. For "seat of the pants" fun, the torque realized from the motor is hard to beat.

Everything the other individuals posted is true of series wound starter motors. High current draw and heat will be your enemy to make a non-continuous duty motor work in continuous duty mode. That being said, I have a homemade go-kart that I made in 2001. It is powered by a Honda 1.3 kw starter motor. I use a Optima brand Red Top battery size group 22. It will last about 1/2 hour to 45 minutes of continuous use, the motor is on and off during this time to speed up and slow down. In the link, my kid's wanted a to drift, the rear wheels have large PVC rings around the tires to reduce the traction.

Without the rings, the go kart will have a top speed of about 25 mph.

If you attempt to use the motorcycle starter motor, I would ensure you disassemble the motor and hopefully it will have bearings at each end and not bushing, if it has bushings you will need to re-grease the bearing surfaces. But I would pass on this motor and find one with real bearings.

Bench test the motor in vise to ensure it runs freely.

Then make heat sinks to attach to the motor case.

A fan would help too, but must be sized correctly to be of any value.

Use large gauge power wire, I use 0awg made for car stereos, for your motor 2 gauge battery cable will work, but the larger the diameter the better.

Its great to hear this from someone that actually built this. I will see what I can do tomorrow! Thanks!


4 years ago

It's probably a series DC machine designed to survive running a battery down once
or twice a year.
You should get four blocks trajectory out of a battery with it and be ready to fry an egg on the motor frame shell.
How many commutator bars does it have ?

Can you explain what you said like a noob? I am not good at electronics.

A starter motor is ;
  • Used infrequently
  • Made as small as possible
  • Has no provision for cooling
  • Expected to cool down by radiation and convection to ambient air.
  • Designed to survive running continuously until the supplied battery runs down ie battery gives away all charge current and can't turn starter another revolution very very rarely.
  • A very hot motor after sucking the battery, so hot you can fry eggs on it.
  • A series motor ie the armature is wired in series with the field windings
  • A motor whose torque increases as it is loaded and speed comes down and current and heating goes up.
  • The number of commutator copper bars that the brushes pass current to the armature decides how effective the machine could be at propulsion.
  • A machine that draws heavy current draining a battery and getting so hot that you might make a vehicle that could travel 4 blocks before the motor burned-up or the battery drained empty.


Starter motors are not designed for prolonged running. If you try to run it like a regular motor you will burn it out rather quickly.

I have seen a guy saying he built a go-kart with a starter motor, and it lasted for years. I would change the grease to oil, and maybe do some holes on the brushes for better cooling.

Ran the cart at half voltage or lied

Its not well suited to the job. Starter motors provide huge amounts of torque, but not for very long.