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!

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Step 1: 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

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

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

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.

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!

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!

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!

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    41 Discussions


    Question 1 year ago

    Is it possible to add piezoelectric battery (self charging batteries)to the motorized bicycle?


    Question 1 year ago on Introduction

    Please could you email me at...
    as I need help finishing off the last bit of my engine bicycle, as the small chain cog (image No.1) won’t turn when feeding through the chain . I will email you straight back once I receive a message from you. I also have a few questions about the other images I sent you

    1 answer

    Answer 1 year ago

    I'm trying to remember from when I built mine, but I believe that you need to have the clutch cable rigged before you can run the chain. This is very difficult because you need to disengage the clutch by pulling on the cable with a tool (such as pliers), then run the cable to the clutch handle while it's in the engaged position (Squeezed). Once the cables rigged you can release the clutch handle so it can return to neutral (the position it would be in if you were not squeezing it). This will allow the clutch to re-engage the sprocket and not allow the chain to move. This is essential because this is how you kick-start the motor to allow the motor to run.

    While it would seem easier to run the cable from the clutch to the clutch handle while the clutch handle is disengaged, this will generally not work because the clutch handle does not have enough travel (throw) to fully disengage the clutch when it's squeezed if it's rigged in the slack position. Additionally, the cable itself will stretch and slacken up over a period of time.

    Based on your photos, I would say that the next best possible move for you to do is to load up the entire bike and take it to a very friendly local bike store where they can finish the rigging for you and give everything a generally look over before you actually start riding it. Not a boutique where they have nice polished floors, sell 1000 dollar bikes and charge block rates like a menu, but a real bole store where they operate out of an alley and the mechanic smoke Marlboro unfiltered cigarettes and is probably missing a pinky finger from a unrepayable debt. These are the types of shops that will work on projects like this.

    Based on my experience with my motor bike, it's best to let the bike store handle the bicycle aspects of the project. The other areas that you are going to need to pay attention to is the rear hub. You need to make sure the rear wheel is true'd out and the rear hub isn't over tightened, otherwise you'll almost immediately burn out the bearings. I got lucky because the shop was able to repack the bearing for 10 dollars, but if you don't get that kind of service then you'll have to replace it with a 100 dollar aftermarket hub.

    Make sure the rear sprocket is on dead center straight, and make sure that the chain guide (The secondary sprocket that the chain rests on) is tightened as well and wont get sucked into the wheel. Make sure the excess slack is taken out of the main chain so there's not excess slack. I got lucky and the length of my motor to sprocket was just right so I didn't need to make any changes to the chain.

    Lastly, make sure the front brake is up to specs. Your rear brake is almost worthless in these applications and the front brake will do the majority of the stopping. Again, your local bike store can check to make sure everything is within spec.

    Good luck!


    2 years ago

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


    3 years ago

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


    3 years ago

    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

    4 years ago

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


    Reply 4 years ago on Introduction


    4 years ago on Introduction

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


    5 years ago on Step 5

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

    1 reply

    Reply 5 years ago on Introduction

    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.

    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.

    2 replies

    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.


    Reply 6 years ago on Introduction

    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.


    6 years ago on Introduction

    Roughly 42 Kilometers per liter. It's literally a non-issue.