Introduction: Motorized Bicycle Assembly Overview

Picture of Motorized Bicycle Assembly Overview

This is a short instructable on how to assemble a motorized bicycle. This was my project when I first started with Tech Shop. 
What's important to remember when you do this project is that not all the bikes will be the same, there are subtle differences that you have to be aware of, and your mileage may vary as far as the degree of difficulty on assembling bikes. Have fun!

Step 1: Step One! Educate Yourself!

Picture of Step One! Educate Yourself!

Before you start this project you have to know what your doing! There are many variables to consider so you have to have a good understanding of what your getting into!

The bike is important! Do not get a cheap bike from Wal-Mart or Target! The construction of the frames are light and could split from the vibrations of the motor. At the very minimum, you should source a bike from a local bike store that is sturdy. A beach cruiser frame is the best option. 

The motor you use is important. Most places on the internet will offer motor kits for your bike. These are universal kits and may not fit your specific application. Be careful before you order as most places have a no return policy. 

The style of bike is important. Going for a vintage look or rat rod look may be your best bet. 

Step 2: Prep the Bike

Picture of Prep the Bike

Your bike is going to be going a lot faster with the motor on it and the demands are going to be exponentially higher. Make sure you prep the bike for this higher duty. Safety is key here. 

In this example, I added a front caliper brake to assist the coaster brake with braking, and replaced the stock inner tubes with puncture resistant inter tubes. 

Once you add the motor to this bike, the weight will increase drastically and you do not want to have to carry this thing home!

You can also personalize your bike to make it a personal fit. In this case, I powdercoated the bars and seat springs to match the whitewalls. 

Step 3: Get the Motor

Picture of Get the Motor

Most kits will come similar to what you see in the picture. Just a bunch of random parts, unlabeled bags full of screws, nuts and bolts, and no instructions. To make it even more fun, parts might be missing, stamped improperly, or just fail to show up to the party as far as quality of work. 

Don't panic, think logically. It all has to go together somehow. You might have to retrofit some pieces or custom grind others.  It's all part of the game and will make victory that much sweeter. 

Step 4: Test Fit the Motor on the Bicycle

Picture of Test Fit the Motor on the Bicycle

Test fit the motor on the bicycle frame. It should fit snugly onto the frame. If it doesn't, then you need to make whatever modifications are necessary to get it to fit snugly. This may require fabricating new brackets for it.

This is the most important step in the process. The motor will have a lot of stressed being placed on it and it absolutely cannot be compromised. These motors have been known to fall off the frame in mid-drive when improperly mounted with catastrophic consequences. Make sure you secure it down. 

Step 5: Attach the Rear Sprocket.

Picture of Attach the Rear Sprocket.

Most kits will come with a rear sprocket that you attach to the rear wheel. This rear sprocket is connected to the motor and is the primary drive gear for your rear wheel. The most important thing to remember is that this sprocket, when mounted, has to be absolutely dead on in distance from the wheel all the way around. There cannot be any wobble what so ever when the wheel spins  or you run the risk of throwing the chain during operation. 

A near fanatical measurement process is not necessary, but could be helpful!

Step 6: Hook Up the Drive Chain!

Picture of Hook Up the Drive Chain!

The drive chain is what carries the power from the engine to the rear wheel. This is the part of the drive train that is the most fragile but also see's the highest workload. If this fails, it can be catastrophic so you have to make sure that everything is lined up perfectly straight. Variances are not much, and you may  be able to get away with a few millimeters here and there but the chain will run a risk of jumping the teeth is it is any more then that. 

This is also the stage where you will discover if the kit will actually fit your bike or not. Generally, if the chain does not hit the drop outs then you are good, but to be safe it's worth getting a beach cruiser frame or you will have to notch the metal where appropriate. 

A side note; most of the chain tensioners that are supplied with the kits are not very good. There is a high risk of the tensioner getting sucked into the wheel and causing an accident. You might be able to get away without running one, (I did) but other have seen a high degree of success by lathing a skate board wheel and making a custom mount. 

Step 7: Hook Everything Else Up!

Picture of Hook Everything Else Up!

After the drive train is successfully connected, its time to assemble everything else as needed. Carbs need to be connected, fuel lines need to be run, clutch and throttle mechanisms hooked up. These steps are equally important but will just result in the bike being disabled or catching on fire if not properly followed. 

It would probably be a good idea to run weather stripping on the wiring. 

Step 8:

Time to drive it and be the boss on the block! Your not going to get far because everybody will want to talk to you and ask you how to build one. Putting one of these things together is an awesome accomplishment! 

Step 9: All of This Was Done at TechShop San Jose!


FilippoRF (author)2016-12-21

Wondering if this will work with a back pedal brake system?

hrtfxr2 (author)2016-10-30

what is the proper fuel mixture? I think this is a 49cc bike. I inheritied it with no instructions.

Olmedo1125 (author)2016-02-19

hi I'm trying to find answer I got my bike w a49cc motor on it but went I get it started and go went I pull the lever that started the bike the handle I'll go faster the only way 2 stop the bike it's the kill bottom any ideas

tanner debernardo (author)2015-10-26

is it possible to put one of the kits in a mt. bike

zerk101 (author)2015-06-09

zerk101 (author)zerk1012015-06-09

skertis (author)2014-12-10

Nice Job! Very well made. To see the basics and more on motorized bicycle's head to

Eldalote (author)2014-06-30

This is sooo cool!

al_packer (author)2014-01-31

And just HOW exactly does the sprocket mount to the wheel? You're leaving out a key part of the process here.

vazquezl31 (author)al_packer2014-04-19

Hello! Essentially the sprocket lays on the outside of the wheel and is secured by nine 10MM (iirc) bolts that thread through the spokes and is secured on the other side by some nuts. The bolts thread through some steel plates and the entire assembly is sandwiched together and cushioned by rubber. I really wish I could get into more detail but that's really all there is to it. Make sure the bolts are torqued down and equal distance to ensure proper spacing on the rear sprocket. Counting the threads helps tremendously.

Too Many Projects (author)2013-02-16

I've done a couple of these and I'll throw in my observations. I used Schwinn beach cruisers, coaster brake and multi speed both. Make sure before you buy a bike that there is room for the motor in the frame. Some are made where there is not as much room between the frame tubes for the motor to fit. You also may need to modify the mounts a little if the frame you get has an oversized frame tube but it's not that hard to modify. I've seen these in everything from a Schwinn Sting Ray (the newer one with the fat rear tire) to some mountain bike frames, though most mountain bike frames don't have the room because of the straight tubes. For me it is vital no matter what bike you start with to repack the wheel bearings. They are fine at typical bike speeds but mine would go 30+ for long periods, and the factory grease job is pushed really hard, subject to failure. You DO NOT want the bearings to go or the front axle to snap at 30. They are fun and legal here in California. About $150.00 for the kit, another $150.00 for a bike and you can sell them for around $500.00-$600.00 dollars.

how much of a difference does it make in the installation process to use a multispeed bike? I'm considering using a 15 speed mountain bike or a 10 speed bike

Hey! Thanks for the input. It definitely counts to know a few good bike mechanics because stuff will break in assembly. I'm personally okay on the motor side but not so good on the bike side. So no surprised my rear wheel was wobbling and about to fall off a few days into the first ride. I was able to go to an old school bike Mechanic and he repacked the generic hub with high tension grease. He suggested I should grade to sealed hubs but understood I was trying to keep costs down. Having a bike mechanic that will meet you half way on that type of stuff goes a LONG way.

piropos (author)2013-02-14

The bike itself is already perfect, why ruin it by putting this engine?

vazquezl31 (author)piropos2013-02-15

Because I'm from Texas and this is what we do. If it doesn't have a motor, we put a motor on it. If it already has a motor, then we replace it with a bigger one. If the bigger motor drinks too much fuel, then we just put a bigger gas tank on it. If the gas tank is too heavy then we put an even larger motor on it to carry the extra fuel. If the motor is already maxed out, then we use two motors. It's not rocket science. That's basically how we went to the moon. BTW, NASA is in Texas so I'd like to think I know a few things about space shuttles and rockets buddy.

Advar (author)vazquezl312013-10-11

Lol, love the play to stereotype answer!
Great project! :)

albpower (author)2013-07-14

I'm sorry I have no idea of this kinds of bicycles how do they work. Can you use the old-way wherever you want ?? for example if you run out of fuel or simple you dont want to use power of motor.

Sorry for this beginner question :(

vazquezl31 (author)albpower2013-07-26

Hello! The engine utilizes an internal clutch mechanism that's hooked up to lever on the left handlebar. If the engine runs out of gas, you can simply squeeze the lever, disengage the clutch which in turn disengages the motor, and you can pedal the bike like normal. The drive chain will still freewheel through the motor so there will be some added resistance an its not optimal, but you won't be walking.

johnny50 (author)2013-02-16

aawwww. just had mine stolen in LEavenworth, KS. Sad.

vazquezl31 (author)johnny502013-02-17

Sorry :(

twighahn (author)2013-02-16

where did you get the motor?

vazquezl31 (author)twighahn2013-02-17

I purchased the kit over Craigslist. You literally open Craigslist, type in "80cc bike motor kit" and you'll see listings. The 80/66 CC combo is the most popular, and I would skip the 49cc kit. They are all generic, the specific model of motor is usually just a luck of the draw as to when the motor was stamped, but this is something you find out after then fact, not before, Kits retail between 180 - 250 depending on availability.

porcupinemamma (author)2013-02-13

How cool are you?? Fantabulous! Thanks for posting a super Instructable! All the best, Lyn

Thanks Lyn!

andrea biffi (author)2013-02-14

nice project, I like the final result!

vazquezl31 (author)andrea biffi2013-02-15

Thank you! It took a lot of work and I admit I'm overwhelmed by the reception. I think I did catch a little lighting in the bottle with the whitewalls and the matte black paint job but all in all, I think it's a good combination.

wobbler (author)2013-02-12

Nice job! What is the speed and approx range on a tankful or rough mpg?

vazquezl31 (author)wobbler2013-02-12

It goes faster then what's really safe and gas is almost a non-issue. I haven't been able to get a rough estimate because I've yet to go through a full tank, even after hours of riding. You just fill it up with mixed two cycle and ride it. You check it every once and a while and eventually you notice it's getting empty and you refill it.

Specs say it's 25 MPH tops and 100+ MPG. However, due to the dynamics of this bike there are a lot of variances that go into it. With the nature of the two cycle motor, it's a dirty motor by design and from the get go you'll start fouling the plug and progressively losing performance as you put the miles on it. It will drop off progressively and you won't notice until you pull the plug one day and notice that's it's fouled up. You clean it, restart the bike, and almost get thrown off because of the performance that you forgot that it had.

Nowadays, with modern motors and computer ignitions on bikes, people expect a pretty consistent and reliable motoring experience with every turn of the key. This bike does not offer that. It's a very basic throw back design that beckons to the old school motorcycling experience, for better or for worse. It will drip fluids, mark it's territory, blow smoke, make noises that will have you convinced the motor will absolutely grenade on you any moment, and you'll probably lose more fuel due to leaking fuel lines then actually running through the motor. It's all part of the fun.

In short, you don't buy or build this for the fuel friendly, cost effective commuter alternatives even though that's specifically what they are marketed towards. You build this for the memories and the experiences that you'll no doubt have on this, for better or for worse.

wobbler (author)vazquezl312013-02-13

Thanks for the speedy reply. My first motorbike was a BSA Bantam, which I loved to bits,which it was usually in. It also dripped fluids and fouled its plugs, but it was the best bike I ever owned in terms of memories. First bikes are like like first girlfriends. They msy not be the best, but they are special in their own way.

Keep on truckin'!

Don,t try this at home (author)2013-02-12

I have one of these. Ill give it a week till somthing breaks lol cheep chinese parts.

Hello! The cheap parts definitely do not help but the kits are helpful in terms of teaching how the entire setup goes together. Next go around I'm planning on ditching the kits and going for custom fabrication parts.
That being said there are just so many variables that go into these, but a universal rule is that they require an almost uncompromising attention to detail in assembly.
When I first assembled my bike I had issues with the chain jumping off the cog, and the rear wheel was disassembled and re-assembled many times before I finally got everything in true.
Lock-Tite, proper torque settings, and periodic checks of the rear hub are required, but miraculously the bike has been very consistent and holds together very well. Again, like I said at the beginning it's all about research, the quality of the bike your purchase, and even then, YMMV (Your mileage may vary)

My throttle broke 2 times. the carb is now spiting gas out of the air filter. the gas cap didnt have vent holes so i had to make some. the muffler cap fell off. I think ill go with cheep chinese parts.

rblee (author)2013-02-12

If anyone in the UK (and likely the rest of the EU) is thinking of putting one of these together for road use, don't bother.

It seems that there is no bureaucratic process to issue one with a Vehicle Identification Number (VIN), without which a number of other absolutely vital bits of paper can't be filled in, not least because they're keyed on the vehicle's VIN, so can't be entered into their respective databases.

I eventually got this information from the both the DVLA and the vehicle testing place in Portsmouth, and it was like pulling teeth :(

Still, I'm grateful that I'm being saved from the terror that would surely stalk the land if people rode mopeds that hadn't been flung together in the far east by people paid as little as possible and who thus take an equivalent amount of pride in their work...

vazquezl31 (author)rblee2013-02-12

As always, check with any applicable laws in your area before you assemble this bike.

But everybody knows these kits are for "off-road use only" (wink wink, nudge nudge)

the mechanical engineer (author)2013-02-12

"These steps are equally important but will just result in the bike being disabled or catching on fire if not properly followed."
have to say I love this quote. It's just like "Oh hey, no big deal if you don't hook this up right. Your bike will just burst into flames. Don't worry about it."

Thanks! Considering the primary concern is avoiding the entire rotational drive train mass locking up at speed and dumping the rider, I would say in this rare case catching on fire would be a slightly lower concern on the safety triangle.

About This Instructable




Add instructable to: