The Best Bicycle Motor Kit
Bicycle Motor Kits for motorized bicycles
Best 2 Stroke Bicycle Engine Kit
There are a massive variety of bicycle motor kits. The options can be confusing for consumers who rarely have time to test every motorized bicycle kit available.
Adverts offer sizes 32cc, 50cc, 80cc, 100cc and 200cc bicycle engine kits. Even v twin bicycle engines are available, so knowing the where to start is not an easy task.
To help clarify the confusion, I examine the range of conversion kits.
I break down the advantages and disadvantages of each, to clarify what to expect when you purchase.
I analyse each bicycle motor using 20 years experience fitting, design modifications with mechanics, and customer feedback.
Heads up: Despite the availability of a 200cc bicycle engine kit, the best bike motor kit is the standard 80cc, 2-stroke, bicycle motor kit.
80cc motor kits are strong, reliable, have respectable power. They are also one of the lowest cost of any gas motor for bicycle.
There are good reasons why 2-strokes continue to dominate the gas motorized bicycle market.
Of course, one size does not fit all. There are alternatives that may be best suit a project that you have in mind.
I analyze the benefits of each of the major options to give an understanding of where their advantages lie.
Best Gas Bicycle Motor Kit
Many people have preconceived ideas about engines.
Some enthusiasts prefer 4-stroke brawn over 2-stroke muscle. Others feel that bigger is better, believing that there is “no replacement for displacement”.
This can lead to a poor choice of bike motor that may not suit our frame.
Misconceptions may result in designs being more expensive, more difficult to build, or lower powered, than they could have been.
Marketing rhetoric does not always live up to reality. I’ve learned to test every motor, and performance part, before I listen to a word of the marketing spin that accompanies the product.
To help you cut through the jargon that is spread across every product website, I’ve ranked the best motorized bicycle kits on the market.
I make recommendations considering performance, affordability, and of course, customer feedback.
I have placed a lot of emphasis on the price points of each kit to help you find your perfect match. After all, the big selling point of bike motor kits is that they are low cost.
The first point of clarification is to cut through the marketing hype of cubic capacity. True displacement is often mis-represented because vendors can bump up price for larger engines.
The table below clarifies what the true capacity of each product matched to the capacity stated on the sales tag:
REAL CUBIC CAPACITY
38cc
50cc
70cc
80cc
90cc
100cc
125cc
150cc
MARKETED CUBIC CAPACITY
36cc
49cc
54cc
66cc
72cc
82cc
92cc
138cc
Which bicycle Motor is best?
There is a huge choice of gas bicycle engines. We analyze which is best for your project
200cc Motorized Bicycle
125cc, 150cc and the 200cc bicycle engine kit use 4-stroke pit bike engines.
Although these engines can be fitted, they are very difficult to mount onto a bike frame. If you are able to squeeze a 200cc motor inside the frame, it often require special brackets.
By comparison, bicycle engines have mounting brackets and all the necessary fittings to bolt onto a bike frame. Fitting is, therefore, relatively easy.
The most practical models are between 50cc and 100cc, with the most versatile, cost effective, and most popular engine being 80cc.
2-Stroke vs 4-Stroke
Choosing the correct engine could make or break your project.
As 2 stroke vs 4 stroke is a large factor for many, lets clarify some fundamentals.
Best Gas Bike Conversion Kit
2-stroke motorized bicycles have an advantage in pace, reliability, price, and fuel consumption. There are an endless amount of low cost tuning parts available. It is simple to increase efficiency for a faster top end.
One of the best motors is an 80cc gas engine for bicycle. These can reach 30 MPH, and simple, after market performance parts can easily bump the top speed up to 35+ MPH.
2 stroke bicycle engine kits can reach over 40 MPH with basic tuning. The average DIY enthusiast can achieve this pace without breaking the budget.
Speeds exceeding 40 MPH takes a little more effort and costs ramp up quickly.
Motorized bicycles are small motorcycles
Apart from the size of the engine, there is little difference between a gas powered bicycle and a motorcycle.
Less Maintenance
One of the best parts about 2-stroke engines is that they are easy to maintain. You don’t have to replace the whole engine if something goes wrong. Just about every component is available for a few dollars on Amazon if you ever need a part.
More reliable
2-stroke motorized bike kits are very simple and have far fewer parts than 4-strokes making them more reliable.
Disadvantages
Although 2 stroke bicycle engines have many advantages, they have a high-pitched engine tone. They also require 2-stroke oil to be mixed with the gas which can cause smokey exhaust fumes.
4-Stroke gas powered bicycles
Automatic clutch
The biggest advantage to most 4-stroke bicycle engine kits is that they have automatic clutches and pull start.
The automatic clutch allows the rider to pull from a standing start rather than having to pedal assist the engine away from a stop.
A motorized bike with an automatic clutch is easier to ride as first time riders don’t have to become familiar with a manual clutch.
Quiet
4-stroke bicycle engine kits are also quieter than 2 stoke’s and have a deeper exhaust tone. Quieter engines are an advantage for hunting bikes and can be less offensive if you ride in the suburbs.
Pull start
A pull start system is essential for many conversions (For example, if you are building a slider trike)
Disadvantages
1. Pull starts are very unreliable
It is rare that an automatic clutch is set correctly. They usually need to be adjusted to operate properly.
Most automatic clutch mechanisms are unreliable.
2. 4-stroke systems are more complex to fit.
4-strokes are wider and bulkier than their 2-stroke counterparts. They require a larger bicycle frame to accommodate them. In addition, the pedal shaft has to be widened to allow the pedals to clear the wider casings.
3. 4-stroke bike engines require more maintenance as the engines are more complex
4. They require regular oil changes.
5. Spares are not as easy to find
6. There are few tuning options for 4 stroke motorized bike’s.
7. There are far fewer engine parts available for 4 stroke bicycle engines. If problems occur, a minor fault can require a replacement engine.
8. Cylinder heads on 4-stroke’s are more complex, housing cam shafts, valves and timing chains. The complexity means that the cylinder head is relatively difficult to remove.
9. There are fewer 4 stroke bicycle motors. Performance components for 4-stroke bicycle motors are, therefore, not widely available. Some vendors offer big bore kits but these provide little improvement in speed.
Ranking the best bicycle motors
200cc bicycle engine kit
We rank the different bicycle motors detailing their advantages and disadvantages.
Now that we have covered the fundamentals, the following section delves into the major bicycle motor kits available. I have ranked the kits from best to worst, highlighting the advantages and drawbacks of each motor type.
The winner of the best gas bicycle motor is the 80cc engine kit. 80cc bicycle engines are perfect for anyone who wants to start their first project. They are easy to install, deliver the best bang for buck, and they have heaps of grunt.
Don’t think that if you put one of these low-cost motors on your ride that it will be unreliable. 80cc gas bicycle kits are more reliable, more powerful, lighter, and more fuel efficient than their 4-stroke counterparts.
You will see many thousands of miles on these engines as long as you use good 2 stroke oil mixed in the correct ratio.
Standard 80cc engines are a great platform to start your riding experience. Most often, they are the best option for imaginative projects. They have heaps of torque, fuel consumption of just under 40 MPG, and a top speed is around 28 MPH.
80cc kits have been the most popular option for over 20 years. Fabrication has matured, and brackets, barrel porting, have improved to better the product.
There are lots of low-cost performance parts to tune the engine if you feel you need more grunt.
There are a number of upgrade options for motorized bicycle engines. The most popular upgrade is the Rongtong carb.
The Rongtong is more complex than the NT carb and has a number of advantages. From our troubleshooting point of view, the Rongtong carb has fewer adjustable parts and a different float setup. The Rongtong carb is, therefore,
- less prone to flooding the engine,
- it can tolerate a greater fitting incline, and
- it is unlikely to require tuning adjustments.
If you have verified that the carburetor is working correctly then the following tests are the next stage in troubleshooting starting faults on your motorized bicycle:
The best gas bicycle motor
We rank the different bicycle motors detailing their advantages and disadvantages.
Every vendor promotes high performance bicycle engine kits with a myriad of performance components.
Some vendors offer engines for bicycles with oversized barrel/piston, high compression cylinder heads, Boost Bottles, special barrel porting, reed valves, and many other performance options.
Most vendors just want to bolt on a few eye-catching parts and spin the benefits. Very few “racing engines” perform any better than the base 80cc model.
Looking for the fastest motorized bicycle kit? The standard 80cc with aftermarket carb, power-pipe, and 36 tooth rear sprocket is the best option.
Change the standard NT carb for a Rongtong carburettor and swap the muffler for a good performing expansion chamber.
These simple modifications can drive a smaller rear sprocket. Swapping the standard 44 tooth rear sprocket for a 36 tooth sprocket will increase speed to around 35 MPH.
These low cost options increase power without breaking the bank.
Other components add little value unless you are knowledgeable on tuning 2 strokes.
High compression cylinder heads, Boost Bottles and reed valves add no speed or acceleration, without additional engine adjustments.
“Staged” motors are most often just standard 80cc engine kits with a few bolt on components that simply add cost.
I will mention here that factory built reed valve engines perform very well.
It is, however, hard to know whether the reed valve engine has been correctly designed.
Most reed valve engines are simply a standard 80cc motor with an after market reed valve bolted on. Reed valves do not add power without changing porting.
Factory built reed valve motors have different barrel porting to improve fuel intake.
Unfortunately, bolt on reed valves are common. For improved performance you need to source a rare, factory built reed valve engine, or modify the barrel and piston ports yourself.
If you’re looking for a 2-stroke with tons of torque, the 100cc bike motor is the way to go. As the saying goes, “There is no replacement for displacement” and a 100cc is the largest, purpose built 2 stroke bike motor kit available.
The top speed of the engine is very similar to a 50cc and 80cc motor bike kit but with more torque.
In standard form, a 100cc gas engine for bicycle leaves lower capacity units behind on hills, and acceleration.
The enormous advantage of the additional displacement is the potential to improve top speed. If you want to tune your engine, then the 100cc engine is the best starting point.
The factor that limits the speed of all bike motors is the balance of the crankshaft.
80cc motors rev to around 4,000 RPM in standard form with lighter 50cc cranks typically typically maxing out at around 4,500 RPM *.
A few manufacturers (Zeda for example) have a better balanced crank which can, occasionally, rev as high as 6000 RPM when tuned.
The advantage of the 100cc engine kit is that the torque allows the use of a smaller rear sprocket. 100cc engines can use higher gearing to provide higher top speeds than other bicycle motors.
The downside of 100cc engines is their cost. Around twice the price of an 80cc alternative.
An 80cc engine with expansion chamber, sports carb and smaller rear sprocket will outperform the 100cc engine for less money.
Standard 100cc motorized bicycles will cruise at 35 MPH when fitted with a smaller rear sprocket.
This is the first 4 stroke conversion kit on the list. If you must have a 4-stroke then the 200cc bicycle engine kit is the stand out amongst these engines.
The key feature of bicycle motor kit 4 stoke is that they invariably have automatic clutches.
Advantages
Automatic clutches provide an enormous advantage for some riders. The feature makes the bike easier to operate and adds the ability to pull away from a standing start without pedalling.
Pull start mechanisms can be essential for some projects (slider trikes as mentioned before).
The third benefit of a 4 stroke is that they are relatively quiet and most people prefer the engine tone.
Finally, you do not have to mix oil with the gas although they do require regular sump oil changes.
Negatives
4-stroke’s are easily outperformed by smaller 2 stroke’s.
The very features that distinguish 4 stroke are also their downfall:
Automatic clutches are rarely adjusted properly. The bike has to be revved extremely high to engage the clutch. The clutch then grabs, and jolts the rider forward.
Alternatively, the clutch engages at low revs and the motor struggle to pull away from the sidewalk or stalls frequently.
Adding to the problem is the pull start which is seldom set properly.
Often, the start cable will extend 3/4 of its travel before it catches the pull-start mechanism. This can make the motors difficult to start.
- The pull start mechanism is also unreliable and I often encounter pull starts that break after only a few days of use.
- 4 stroke’s are underpowered and more expensive than their 2 stroke counterparts.
- 4 stroke gas bicycle engines are bulkier, and wider, making installation more difficult. They require spacers to allow the bicycle pedals to turn, (rarely included in kits).
- Mechanics are less reliable than other two strokes because of the increased complexity.
If you purchase a 50cc 4 stroke, you can expect a cruising speed of around 20MPH. If you want power, a 200cc bicycle engine kit is the way to go, despite the difficulties in fitting.
What can I say but the speciality of this Canyon MTB is in the name – It is ideal for Canyon biking.
Click here for the full Spectral review.
Friction drive engines are compatible with just about every bicycle frame. Friction drive motors are perfect for anyone who has a frame that isn’t suited to a regular bicycle engine kit.
Friction drive’s rest directly on the bicycle tire. These bicycle motors can therefore power a bike with any size wheels.
These rigs are the easiest to fit and can be attractive for ease of installation.
Negatives
The drawback to friction drive’s is that they are small capacity, high revving, low torque appliances.
Friction drive engines can help push the bike to around 15 MPH, however, they lose traction in wet weather, or when trying to power the bike up hills.
Reliability
Friction drive motors re-purpose high revving, brush cutter / chain saw parts. They are, typically, less reliable than purpose-built 50cc, 80cc, or 100cc bicycle motors.
Conclusion
How to motorize your bike
We have improved and updated our fitting instructions to include the latest updated components.
If you are building a motorized bicycle, there can be a large variance in performance of one brand bicycle motor over the same product from another manufacturer.
If you want to pep up your wheels, the best option in most situations is the 80cc 2-stroke.
There are, however, good reasons to purchase other bicycle motor kits:
- 100cc 2-stroke engines have most power,
- 50cc 2-stroke engines have the best fuel consumption,
- 4 stroke engines are quieter and have automatic clutches
- friction drive motors are easiest to install.
Whatever your choice, bicycle engine kits are great fun, cheap, useful, and environmentally friendly.
