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The Safety Issues and Other Problems with a Moped
or a Motorized Bicycle

 Copyright © December 1, 2010 by Robert Wayne Atkins, P.E.
All Rights Reserved.


Moyotized Bicycle The gasoline bicycle engines that are currently being sold come with a disclaimer that says that bicycles equipped with one of these engines can be extremely dangerous and serious personal injury or death could result. The manufacturing company and the seller both disclaim all liability for any type of injury and the buyer assumes all the risk of injury and the buyer will hold the manufacturer and the seller blameless. This statement is not just some legal mumbo jumbo. It is absolutely necessary because a bicycle equipped with one of these gasoline engines is extremely dangerous.

In June of 2010 I purchased a specially designed gasoline engine and I began the process of installing it on a bicycle in my spare time. In July of 2010 I completed the installation and I was able to test my new motorized bicycle. Within ten-minutes I had a serious accident with my "new motorized bicycle." Fortunately I was wearing protective clothing and a motorcycle helmet and, by the grace of God, I walked away from that accident with only a few really serious bruises and a few minor cuts. However, my close encounter with a permanent disabling injury, or maybe even death, caused me to put my "new motorized bicycle" in the garage until I had the time to objectively consider what had happened and why it happened.

Almost five months have passed and after much careful reflection and consideration I believe I am now in a position to render an objective unbiased opinion on the safety issues with these modified motorized bicycles. I am presenting the following information as a public service in order to help you better understand the current safety problems with these motorized bicycles based on their current design.

(Note: I purchased my first motorcycle when I was twenty-years old. During the course of my life I have owned and ridden four different motorcycles. I currently have an "unrestricted motorcycle license" as part of my state drivers' license which means I am qualified to operate any motorcycle of any size, including the really big motorcycles. Therefore, please do not discredit the following comments based on the invalid assumption that I am a novice and that I have no previous experience with motorized two-wheel cycles. I have over forty-years of experience operating motorcycles and my accident was not the result of an oversight on my part or any lack of experience on my part.)

Following are some of the problems with the current "motorized bicycle" design:
  1. The clutch lever and the front wheel brake lever are both hand operated and they are both mounted on the left handlebar. This means you can't operate both of them at the same time. This is a serious safety issue. If you need to apply the brakes then you also need to pull in the clutch. If you don't pull in the clutch then the engine keeps working against you pulling you forward while you are trying to stop the bicycle with the brakes. If you pull in the clutch but don't apply the brakes then you begin going faster because the engine is no longer engaged and you are free-wheeling. Therefore, regardless of which lever you pull with your left hand, you are going to have a problem stopping your bicycle. (Note: The manufacturer has installed an engine shut off switch on the throttle control on the right handlebar so you can "kill" the engine every time you need to stop. However, this does not resolve the safety issue with the two left handlebar controls.)

  2. The front and rear brakes on a bicycle are designed to stop the bicycle at normal riding speeds, which for most of us is ten or twelve miles per hour or maybe slower. The brakes are not designed to quickly and safely stop a bicycle traveling at twenty or thirty miles per hour. Therefore the total stopping distance is a lot more than what you would expect. This becomes a serious safety issue when you must stop unexpectedly and there is not enough distance between you and the object you are about to collide with.

  3. The new gasoline engine would not start. To start the engine you have to be pedaling the bicycle extremely fast or riding the bicycle down a hill. Even at six-miles per hour the engine would not turn over. At 6 MPH the engine made a sound similar to what you hear when you turn the ignition key in an automobile and the starter engages. The bicycle engine sounded as if it was trying to start but it just wouldn't start.

  4. There is an idle adjustment screw on the engine but there is no information about an optimal initial setting. There are no instructions that tell you approximately how far that screw should be turned to get the engine to start and to remain running on idle. This is a trial and error process and when you begin you have no idea of whether or not you are even close to a reasonable idle setting.

  5. The engine choke control is on the engine far below the bicycle seat. The choke needs to be engaged to start the engine and then disengaged after the engine is running smoothly. Reaching down between your legs and trying to find the choke control on a hot bicycle engine is not easy to do.

  6. The wiring diagram and colors in the instruction booklet that comes with the engine do not match the actual wiring on the engine itself. The instructions that you download from the web site also do not match the current wiring colors or configuration. After requesting additional information by email I was able to wire the engine based on the information in the email. But since the engine still would not start there is a chance that the final wiring connections are still not correct.

  7. The exhaust pipe has a 90-degree bend. It needs at least a 105-degree bend. I took the exhaust pipe to two different muffler shops, a bicycle repair shop, a motorcycle repair shop, and a metal fabrication shop, and none of these shops would accept the job of bending the small exhaust pipe because it did not match any of their current bending dies. Therefore, I put the exhaust pipe in a bench vise and applied heat with a propane torch and I was able to add about five or six extra degrees of bend to the exhaust pipe. This was just barely enough to get it to fit on the bicycle but it was still mounted too close to the ground. If a little more bend could have be added without crimping the pipe then the exhaust pipe would have been higher off the ground and closer to the lower frame of the bicycle. The company that makes these exhaust pipes should increase the original bend from 90-degrees to at least 105-degrees.

  8. Do not buy the optional pull start attachment. Although this looks like a good idea you have to replace the center pedal shaft and this puts the pedals further out from the bicycle which is not comfortable for most people.
Following are some additional safety issues with motorized bicycles in general:
  1. The average motorist does not understand that a motorcycle cannot stop in the same distance as a bicycle. Many disabling accidents and deaths each year are caused to motorcyclists due to a driver pulling out in front of the motorcycle and the motorcycle not being able to stop in time to avoid hitting the vehicle.

  2. The average motorist will not see the motor attached to your bicycle while you are riding in a straight line directly towards the motorist on a side street. The motorist will simply see a person on a bicycle and therefore believe he or she has plenty of time to pull out into traffic in front of you and that there is no possible way you could cover the distance from where you currently are and where the motorist is. What the motorist doesn't understand is that you are traveling at 20 to 30 miles an hour and not 5 or 10 miles per hour. Therefore the motorist will simply pull out in front of you and you will not be able to stop in time to avoid hitting the car that is now directly in front of you. One of your options will be to swerve off the road into an area where you can't safely steer and have a serious accident while the motorist continues on unharmed and unaware of your injuries or even your death.

  3. Motorists traveling on the road in the same direction you are traveling will become impatient driving behind you and some of them will pass so close to you that they actually force you off the road as they turn back into your lane. Again you will be the victim of a serious accident but the motorist will continue on either unaware of your accident or simply thinking that you just had a simple bicycle accident and you will soon get right back up and start riding again. The motorist will be wrong. You will be either seriously injured or dead.
The above problems are the reasons I cannot recommend a gasoline engine for a bicycle at this time. The reason I purchased this particular engine was because of several positive customer reviews on the seller's web site but at this time I am not convinced that those reviews are representative. My suggestion is that you wait until the following design problems are corrected before attempting to modify an existing bicycle with a gasoline engine:
  1. The clutch and the front brake need to be operated at the same time and this can't be done with the same hand. Some other system needs to be devised to allow you to operate both at the same time in a safe manner.
  2. The braking system needs to be improved so that it will safely stop the bicycle in a reasonable distance if the bicycle is traveling at twenty or thirty miles per hour.
  3. The wiring diagram needs to match the current configuration and it needs to work.
  4. The idle screw should be factory pre-set at the optimal setting and the instruction manual should explain how many turns or partial turns this actually is.
  5. The choke control on the engine needs to be designed with a pull lever (in and out) that mounts on the handlebars so the choke can easily be engaged and disengaged by the rider while in a normal sitting position on the bicycle seat.
  6. The muffler pipe needs to have at least a 105-degree bend in it.
  7. The engine needs to start at five or six miles per hour. It should not be necessary to get the bicycle to ten or twenty miles per hour to engage the engine. (Note: One solution to this problem would be to install a six-volt engine starter that could be connected to a six-volt front headlight battery.)

The Quality of the Cheap Engine Kits Made in China

The cheap engine kits that are made in China don't work right out-of-the-box because they are "cheap." In other words, they are poorly engineered and made with inferior component parts. Over the years they have corrected some of their serious design problems but these motorbike kits are still cheaply made.

As you attempt to install one of these engine kits on your bicycle you will have to make frequent modifications to the kit parts just to make the engine kit fit on your bicycle. This is very frustrating. And when you finish the engine still will not start. That is when you will decide to do a little internet research that a smart person would have done before beginning this project. On the internet you will discover that there are a multitude of design problems with these bike engines that you are going to have to fix yourself if you wish to have a working motorized bicycle. Suddenly it dawns on you that this is not going to be as affordable or as easy as you originally planned. When you consider all the additional time and extra money you will have to invest to get your motorized bicycle operational you will probably decide that it is just not worth it.

This is similar to the card game of Poker when you realize you are beaten and your best option is to fold in your hand and not keep "throwing good money after bad." In Poker the bad money is the money you have already put into the pot and you know it is lost. The good money is the money you still have in front of you and which you will lose if you decide to play the game all the way to the end. A smart player will fold his or her hand and not waste any more money on a losing hand.

One web page where you can read the advice of another person who has quite a bit of experience making these cheap engine kits work is at the following link: http://www.motoredbikes.com/showthread.php?t=13287
The author who wrote the article at the above link has a list of 33 different things that need to modified or replaced for the bicycle engine to work the way it should, such as immediately replacing the spark plug, getting the rust out of the inside of the gas tank, replacing most of the bolts and washers with American made quality parts, and bending the exhaust pipe in a vise.

Individuals at other "trouble shooting web sites" recommend drilling out the fuel intake port to keep the engine from stalling. If you will take the time to research the problems with these cheap bicycle engines from China you will soon realize why they are so "cheap."

Finally, if you do decide to invest the time and money to build a functional motorized bicycle, then you need to ask yourself this one last question:
Do you really want to end up permanently disabled as a result of an accident while riding your new toy?


The following information is being provided in the event
all the above problems are corrected at some time in the future.


Review of the Current Standards for Motorized Bicycles in the United States

In order to be classified as a Motorized Bicycle in most states within the United States of America all the following conditions must be met:
  1. The engine must be under 50cc if operated on gasoline or under 750 watts if operated using electricity.
  2. The top speed may not exceed 20 mph in some states and 30 mph in other states.
  3. The cycle does not require clutching or shifting gears when using the motor.
Advantages of a Motorized Bicycle:
  1. They are not subject to motor vehicle registration so you don't have to buy a vehicle tag.
  2. They don't require insurance so you don't have to add them to your vehicle insurance policy.
  3. Therefore no one other than yourself and your family members would know that you had an emergency motorized bicycle.
A brief summary of some of the more common rules and laws that apply to Motorized Bicycles:
(Note: Verify the laws in your state by doing a simple internet search as follows: moped laws "your state".)
  1. The cycle may have either two or three wheels.
  2. The cycle may also be operated using ordinary foot pedals and human leg power.
  3. The operator must usually be at least 15 years old and have a valid driver's license or learning permit.
  4. The operator must wear a motorcycle helmet. In some states an electric cycle operator may choose to wear a standard bicycle helmet instead.
  5. The operator must obey the same traffic laws as operators of other motor vehicles.
  6. They may not be used on limited access highways, such as interstates, or on any highway with a posted minimum speed of at least 35 mph.
  7. If there is an approved bicycle lane then the operator must use that lane instead of the normal roadway.
  8. No more than two cycles may be ridden beside each other at the same time.
  9. No cycle may be used to carry more people than the number it was originally designed to carry.
  10. All cycles operated at night shall have a front white light visible from 300 feet in the front and a rear red reflector or a rear red light visible from 300 feet to the rear.

Schwinn "Point Beach" Seven-Speed Road Bike
(Cost approximately $174.00 at WalMart)

  1. The open space in the frame is big enough to easily install a gasoline engine without having to make any type of modification to the gasoline engine or to the bicycle frame.
  2. It has seven-speeds which provides all the basic options for road travel. Only the rear wheel has multiple gears so there is only one gear selector on the right handlebar. There is no need for a separate gear selector on the left handlebar because there are no additional gears at the pedal area. This is a significant advantage when installing all the engine options on both sides of the handlebar.
  3. It has wide 2.125" tires for maximum contact with the highway for stability and maximum contact with the highway when applying the brakes. These 2.125" highway tires are 9% wider than the 1.95" tires that come as standard equipment on a "mountain bike."
  4. A sturdy rear luggage rack is already installed. However, due to its substantial design it will not accept standard bicycle saddlebags (panniers) that are designed for the thin metal wire luggage racks.
  5. A wide comfortable seat is already installed as standard equipment.
  6. It has high long front handlebars with lots of space to attach the additional motor controls.
  7. The high long front handlebars allow you to sit upright while steering the bike. This is a more conformable sitting position for long road trips.
  8. It has a chrome front fender to keep road dirt and moisture off you, your bicycle, and your engine.
  9. It has a chrome rear fender to keep road dirt and moisture off whatever you are transporting on your rear luggage rack.


Different Types of Engines

  1. Gasoline or Electric.
  2. Friction Belt or Chain.
  3. Above Rear Wheel or Between Pedals.
At this time I will not discuss the advantages and disadvantages of the above three options because at this time I cannot recommend any of them.

However I did want to briefly mention them so you would know what the different options are.


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