Before I start I would like to press a major safety issue. Please always wear a helmet. I recently got into an accident and it would have been much worse without a helmet . WEAR A HELMET!
Okay now to the stuff you came to read and see. I completed this project with a friends help way before I started making instructables. So there is a little bit of step-by-step but not much. Even if there was the build is very subjective to the bicycle on hand. We built this bicycle on a decent budget without breaking the bank on a $660 Golden Eagle kit. In total I think it was about $575 to have a complete fully upgraded motorized bicycle which is still less than the kit or buying those silly Chinese kits. The bicycle I have is a Walmart Schwinn, the reason for it was I wanted nice accessories over a nice frame. The bike is heavy and a lighter frame would help but doesn't stop it from reaching a top speed of 30mph on a flat. I cruise at a comfortable speed of 20 mph I don't believe in W.O.T. (wide open throttle) an engine for more than 30 seconds and like keeping it at about 2/4 throttle. Anyways to the shopping list and what it cost me.
To start the shopping list this is what I bought:
In total before upgrades it only costed roughly $280 to have a motorized bicycle. But as described in my last part of this instructables you have to upgrade some parts like the tires, rims and other equipment you want on the bicycle. I will say it was a tricky to build because you have to measure twice and cut once. I already built it so it's hard to describe how it was built and put together.
Please leave a comment if you have any questions.
Step 1: Why This Motorized Setup?
First off there is a dizzying array of motorized bicycles and different ways of doing it. I'm not claiming this is the best motorized bicycle but, it's better than most. The most common is the "80cc" Chinese kits that are utterly cheap and people (like me) will and have wasted time and money on them. I could go off on a tangent about them but I wont so moving on. The next one is friction drive which involves a metal rod that sits on the tire. The problem is they are useless when it rains and eats your tire alive. Then there is Staton with it's very own confusing selection of engine kits. Finally we come to the best option Golden Eagle, with it you can go three ways with the design. First is buying the kit flat out for $660 which is the quick and easy way of doing it. The second is buying their mount kit which is great if you have a mini 2 stroke or four laying around. The last one is what I did, by buying some parts from their site and building it from scratch.
Step 2: The Motor
You can use a Honda GX35 but they cost $250 brand new if you want. On this I used a Honda GX31, it's a 31cc engine, 4 stroke, quiet running engine, and about 150 mpg. Golden eagle explains why a four stroke is great to use towards the bottom of the page here. Be aware when buying a GX31 that there is a tiller version and a trimmer version both will work but the trimmer style air cleaner works the best. The engine can go up grades but can't go up anything major without pedal help (it's a 31cc engine it can't work miracles). On Golden Eagle you can get a #11 high gear for hilly terrain, #12 the all a round gear, #13 the highway gear for flat terrain. I went with the number #12. The gear size will also depend on the size of the engine you use.
Step 3: The Motor Support
The way you build the support will solely depend on the bicycle you have. It must have a solid axle no quick releases! Why? The aluminum plates get bolted right on to the axle. There needs to be at least 3 points of contact for the frame. Two of them must be on the axle and one needs to connect to the frame to prevent the engine from twisting. The supports are made out of aluminum because it is lighter and doesn't rust. You can use steel just be a little heaver and you could weld instead of bolting it up. The aluminum was cut using a simple band saw just be sure to use cutting oil. Then edges where rounded off with a sander (makes it look professional).
Step 4: Bicycle Upgrades
In this step show you how to make a bicycle ready to accept it's new motor counterpart. I am creating this because there isn't much information on the bicycle upgrades when adding a motor. More times then not the standard bicycle rim and wheels can't take the abuse. I will present the things I had to do to upgrade in a few steps so hopefully you wont make the same mistakes/discoveries as I did.
The first items to go on my Schwinn are the cheap tires. Please I beg of you!!! Go to a bicycle shop (local preferably) and get wonderful flat resistant tires they are well worth the money especially on a motorized bicycle. I got Bontrager tires and they are amazing I have never had to worry about flats. The rim had to be replace after spoke after spoke broke. Tongue twister! So I decided on a custom rim from Sugars in Portland, OR and had one handmade they even soldered the spokes. I know that sounds outrageously expensive it's not it is well worth the money considering the cost of spokes and truing the wheel. Also I have a horn for special events and or to warn cars, bikes, and pedestrians that get in my way hehehehe.
Step 5: Upgraded!
Here are the upgrades on the motorized bicycle. These upgrades in my opinion are very necessary to have a reliable commuter motor bike. I've gone at least 400 miles so far without a lick of mechanical trouble. Hope this helps those of you thinking about a motorized bicycle design.
Feel welcome to comment or ask questions below