Mini Motorcycles, Their Types, Uses, and Limitations

Mini bikes, mini motorcycles, minibikes, whatever you call them, are kids motorcycles that are usually 50cc or smaller and are designed for children, but they can be just as much fun for adults. These kids motorcycles are small but faster than you would expect. They are certainly fast enough for any 9-12 year old. Usually, these bikes will reach speeds of between 20 and 30 miles per hour. This may not seem like much when you think about it compared to driving or riding a full sized bike, but for a child, this is flying. If you want to see some examples, read our best mini bikes review. If you’re looking for something even smaller than the mini bikes you see here, you might be looking for a pocket bike. We’ve written an article about the best pocket bikes as well!

honda-z50-mini-motorcycle-725
Honda Z50 Mini (Author Holger Sahlmann)

When I was about 8 I got my first motorcycle. It was a Honda Z50 mini bike I got for Christmas. With the exception of my Harley Iron which has taken me from Birmingham Alabama to Albuquerque New Mexico and back I have spent more time on that minibike than I have on any other motorcycle I have owned since. I, like many others, learned on this bike. These are specifically designed to be kids motorcycles and they serve their intended purpose quite well. They are usually fairly cheap which is good since they usually only get a few years of use before the rider outgrows them and they tend to suffer from above average abuse, they are small to accommodate younger riders, and because of their small size and displacement, they are forgiving. A larger bike would be much more likely to get out of hand with a new rider than a mini bike because they are taller, heavier, and more powerful.

My first bike will always hold a special place in my heart. I don’t think anyone forgets the first time they kick over and engine and hear it start up. It really is one of the best sounds I can imagine. It wasn’t perfect, I crashed, I fell, I burnt myself, got cut up, may have gotten a fracture or two, but one thing is for sure. At the end of the day, riding is worth all of it. If you have a passion for riding or your child is inclined towards it, a minibike is a great gift and one that can change their lives forever. No one is going to remember how much it hurt when they ran into the fence for the first time, but everyone is going to remember the thrill of their first jump or sliding around a corner in the mud so you don’t lose speed. This is where it all starts. Learning to ride at a young age on a mini bike will foster a lifelong love of motorcycles.

Mini Motorcycle transmissions and their impact

Most gas powered mini motorcycles will have some form of semi-automatic transmission. Because of this, a new rider can shift without actually using the clutch and not damage the transmission. Admit it, we all did it when we first started out. These are the things the manufacturers try to plan for when designing these bikes.

The larger brands like Honda and Yamaha obviously have an advantage here, but if you want something new and cheap there are options out there. Several Chinese brands can be bought on Amazon and shipped right to your house without ever having to meet with a dealer or go through the trouble of buying one on a site like Craigslist. A semi-automatic transmission has the advantage of teaching a new rider how to shift while not punishing them for not having developed the skills yet.

Automatic Transmission mini motorcycles

Some of these mini bikes come with an automatic transmission. These are generally going to be CVTs, that is Continuously Variable Transmission. These work by using two “spools” that expand and contract according to the engine speed. The front spool is smaller when the engine is at idle or lower RPMs but uses several weights to expand as the engine speeds up. This front spool is connected to the rear by a belt. As the front spool expands the tension on the belt causes the rear spool to be split. The rear spool is pushed together by a spring, but as the engine speeds up and the tension on the belt gets greater it overpowers the spring causing the rear spool to become smaller. This combination of spools allows a virtually endless range of gear ratios. These transmissions are also used on most scooters since scooters are typically marketed more towards comfort.

Some of the advantages of a CVT are, obviously, the gear ratios, but also the simplicity. I have rebuilt several CVTs and they are all pretty much the same. Since most CVTs are so similar parts are interchangeable for things like springs, weights, and belts. You can also customize them more than a fixed speed transmission. The bike doesn’t have enough torque? Use a stiffer spring in the back. This will keep it in the low gear ratio longer. What if you have plenty of torque, but want faster takeoffs? Use heavier weights in the front. The heavier weights will overpower the rear spring faster and will allow you to get to a higher ratio faster, thus reaching your top speed faster. These are also super easy to rebuild.

The first one I fixed was on a scooter my dad bought when I was about 15. The guy said the belt broke on him and after that, it didn’t have enough torque to get moving, let alone carry a grown man down the road. Within about 15 minutes I had it disassembles and was checking out how it worked. All in all, the rebuild, which was done without any internet tutorials or prior knowledge of CVTs, took less than 2 hours. These are great if you want something that is going to be easy to ride and easy to fix if something breaks, but they do not offer the experience of a manual or semi-automatic transmission. The main downside with this is that it doesn’t prepare the rider for the manual transmissions found on larger bikes.

Manual Transmission minibikes

Others will have a true manual transmission. These, in my opinion, are the best. They are usually 3 or 4-speed transmissions with a wide ratio and no overdrive. The lack of an overdrive is not a big deal though since you typically won’t want kids going that fast, especially when they are first starting out. There is also the matter of power. A 50cc engine would struggle to power an overdrive transmission. The gear ratios are going to be wider on a 3 speed as opposed to a 4 speed. To put it simply a 3 speed may have ratios of 3:1, 2:1, and 1:1. The 1:1 gear is known as your drive gear by the way. A 4 speed on a mini bike may have 2.75:1, 2:1, 1.5:1, and 1:1. The difference here is that the 4 speed is going to have closer ratios. What this means is that when you shift gears the engine speed is not going to drop as drastically. This allows you to stay more in the power band. With wide ratio transmissions when you shift you may drop well below the power band and have to build back up to it, but with a close ratio transmission, you are going to stay close to, if not in, the power band. This provides faster, smoother acceleration because engines typically make the most power in a fairly narrow range. As you have probably guessed this is called the power band. This is the reason 4-speed manuals overtook 3 speeds in cars. While both have the same final ratio of 1:1, the closer ratios in the lower gears make all the difference while you are riding. They simply allow you to have more control of the engine speed at any given time.

Manual transmissions are generally going to be more reliable than CVTs or semi-automatics. The reason for this is that a manual is completely controlled by the rider, so there are fewer controls to mess up in the case of the semi-automatic, and, in the case of the CVT, there is no rubber belt to break. If your belt breaks on a CVT the front spool will collapse and the weights will spill into it causing a jam. Remember the scooter my dad bought? This is exactly what happened to it.

A standard transmission is a solid chunk of steel with solid gears. The most common point of failure in a manual transmission is going to be the clutch. New riders will tend to burn their clutch when they are first starting by giving it too much throttle, but not releasing the clutch enough. While this is generally not a big deal if it happens once or twice, it can pose a problem in the long run. Keep in mind that clutch packs can be a pain to replace. As a heads up on what to look out for, a burning clutch will smell about like burning electrical wires. The first time I smelled it, I thought my bike was about to self-destruct because the smell was so strong. You seriously can’t miss it.

Another issue that can occur with a manual that semi-automatics prevent is grinding your syncros. To put it simply, a manual transmission’s gears are always meshed, or connected. This is known as a constant mesh transmission. So, when you shift you are not actually moving the gears, but a ring that connects to the gears and transfers the power from the gear to the output shaft. What the syncros do is synchronize the gears and the output shaft so that when a gear is engaged no parts are damaged. If the clutch is not disengaged for this process then the gears cannot sync with the output shaft because they still have a direct link to the engine. The good news is that syncros are much cheaper to replace than gears, so it could be worse. They are typically made of bronze so that if the gears cannot be synced properly the syncro will be damaged, and not the, much more expensive, steel gears.

What is the best mini motorcycle transmission type for you?

Which one is best? That’s a matter of personal choice. Like I mentioned earlier, I am a fan of manuals, but I also have the experience to not burn up my clutch or damage my syncros. For new riders, a semi-automatic is a great option since it teaches them how to shift gears, but is more forgiving than a manual. You may be asking, well, where does this leave the CVT? Experienced riders want a manual and new riders need to learn how to shift properly. CVTs are good for younger children, think 4 or 5-year-olds, and for second minibikes if a rider is already familiar with how to work a manual transmission. CVTs can also be good for practicing control since you don’t have to focus on shift all of your attention can be on total control of the minibike. This can prove advantageous when practicing a particular route or rounding corners. Since there is no need to shift you do not have to worry about being in the wrong gear going into a corner. Again, this is not something that will matter to a veteran rider, but to a beginner it can make a huge difference.

Chinese vs Japanese mini motorbikes

japanese

Nowadays Chinese knockoffs may not be as reliable as their Japanese counterparts they are significantly cheaper and parts are more interchangeable. Most parts on Japanese bikes are model specific, so just because two Hondas have the same size engine does not mean you can use the same head on both. On the other hand TaoTao parts(excluding cosmetic parts) tend to be used on a wide range of models. If I need to replace the head on a 100cc TaoTao I can order a TaoTao head on Amazon for very little, usually around $20, and it will fit my engine. This helps the manufacturer reduce costs(which also helps you save on your mini bike) by being able to order these parts in very large quantities and it helps you because it makes sourcing parts easy and cheap. To give another example a replacement carburetor for a Honda 50cc mini bike like I had can be as much as $50 or more, but a TaoTao(One of the larger Chinese manufacturers) can be as cheap as 10$ or so. Also, since these bikes are usually clones of the Japanese bikes if a part is known for failure it can usually be replaced with a Honda or Yamaha part without modifications. Most of these tend to be Honda clones, Yamaha clones are a bit harder to find. Whether the engine on your bike is a clone can be difficult to find out since they don’t advertise it. But you can usually find reviews or forum posts from people who have bought them and swapped in real Honda parts.

The downside to this interchangeability is that it can sometimes be difficult to determine if a part is the right one. You may not be able to find parts numbers as easily as with the Japanese bikes and the support from these companies is virtually non-existent.

Other important factors when it comes to mini motorcycles?

Physical Size of the mini motorbikes

When deciding on a mini motorcycle there are several factors to look for. Perhaps the most important are the physical dimensions of the bike. What good is ordering a kids motorcycle if it is too tall for a child to ride? Conversely, you don’t want to order one that is too small and have a new rider crammed onto a bike that is way too small for them as this can be just as dangerous as a bike with too much power. You want something they can grow into without overdoing it now. The most important thing is that the rider is able to place both feet on the ground. If only one foot can be on the ground at a time or if it takes too much effort to have both on the ground the bike is too tall. The good thing about the size of these mini motorcycles is that once they are outgrown they can be turned into pit bikes. While you could go all out and swap in a different engine, chop the frame and make extensive modifications to the bike most people just opt for a new tank, maybe lower the rear suspension and call it a day.

Engine size of the mini motorcycle

This brings us to the next factor, engine size. Generally, a 50cc 4 stroke is a good place to start, but up to 100cc should be fine for a beginner as long as it is a 4 stroke, not a 2 stroke. A 100cc 2 stroke mini bike is likely to be too much power for a new rider to handle and they could get hurt. Getting hurt is part of it. You don’t learn to ride without making mistakes, I crashed into my dad’s fence more times than I care to think about, but there is a difference between crashing a 50cc 4 stroke and a 100cc 2 stroke. As a general rule of thumb, a 2 stroke is going to be twice as powerful as a 4 stroke of the same size. This is because a 2 stroke has twice as many power strokes as a 4 stroke. The differences between the two are beyond the scope of this article, but just remember that if it is a 2 stroke double the displacement for an idea of the power it has compared to a 4 stroke.

What are you going to use the minibike for?

dirt-road-mini-motorcycle

The third thing to consider is use. What will the bike be used for? Is it going to be a strictly off road dirt bike? In this case, you will want something with narrow wheels, knobby tires, and lots of suspension travel, a true dirt bike. On the other hand, maybe you live in the suburbs and it will mainly be ridden in the alleyway behind the house? In this case, something a bit lower with wider street tires is the way to go. These will not handle the dirt and mud well because of the smooth tires and low stance, but they will have better traction, a smoother ride, and better handling on the street. This is because the tires are wider and smoother which allows more contact with the road. Conversely, a dirt bike needs knobby tires to bite into the ground and keep your wheel from spinning in the mud. You will also want a lower, stiffer suspension. By lowering the suspension, you lower the center of gravity which means less travel is needed to lean the bike and make a turn. This also reduces the risk of high siding the bike. This is where the rider gets thrown off of the bike, but goes over it rather than under. Lastly, a stiffer suspension is going to compress less during turns making the behavior of the bike more predictable. In the case of my Honda Z50, it was something of a hybrid, though it was primarily a dirt bike. The tires were wide, but not overly aggressive, the suspension absorbed bumps well, but was not spongy on the road. It sat high enough to handle some mud and rocks, but not so high that it couldn’t corner easily. These are all things to consider when looking for a minibike and should be considered before making a purchase.

Electric minibikes vs gas minibikes

electric-razor-mini-motorcycle-725

Recently manufacturers have started releasing electric mini bikes. These are usually cheaper than gas mini bikes because they require fewer parts to build. The engine and transmission, both of which are complex pieces of machinery, are replaced with an electric motor and battery pack. The downside to these electric versions is that the top speed is usually limited to under 20mph. This is sometimes due to a governor which can usually be disabled or removed, allowing a higher top speed, or by the size of the motor used which can be upgraded, but it is usually not economical to do so. Some other factors to consider when deciding to between a gasoline or electric mini bike are charging times as these can limit ride duration and riding terrain. While the battery limitations of an electric bike are self-explanatory you must also consider the terrain the bike will be used on. Electric bikes are almost exclusively for on-road use(even if they look like dirt bikes) as mud and water, which unless they get in the intake, are harmless to a gas powered bike can short and destroy an electric bike. That being said, these bikes do have their place. Since they are electric they are almost silent, so no noise complaints from the neighbors if you live in an area where this can be a problem. They also are not usually bound by traffic laws. What this means is that they are essentially bicycles according to the law. Since they are bicycles and not motorcycles the police will usually ignore them. This is the case most of the time with gas minibikes as well, but sometimes you get the one cop who doesn’t like motorcycles, or maybe he’s having a bad day, the point is with an electric mini bike this can usually be avoided.

Electric mini bikes are usually bicycles with body panels and a motor and battery pack. Because of this, they will sometimes have pedals which allow you to ride it as a bicycle if the batteries die or something goes wrong with the bike. This can be advantageous if you(or your child) are out riding and something goes wrong, or the batteries die because you can still ride it home. If something goes wrong with a gas powered minibike you have to push it home of have someone bring a truck or trailer to pick you up, not fun.

Heat production of gas mini motorcycles

Gas engines produce heat and while electric motors do produce heat, the amount compared to an air cooled gas engine is negligible. The benefits of this are twofold. One, you don’t have to worry about overheating while you are taking a break. Idling an air cooled engine is not like idling a water cooled engine. While you can sit in your car all day with the engine running and, assuming you don’t have cooling system problems, never overheat, with an air cooled engine if you sit too long without any airflow over the engine it will eventually overheat and can severely damage the engine. Most newer models will have a thermal shutoff as a failsafe to prevent damaged from overheating. Now I know what you are thinking, what about lawn mowers? You don’t get enough airflow over them to keep them cool while you are mowing grass in 100+ degree weather. Well, you are right, but the difference is in the design of the engine. Lawn mower engines do not need much power, usually just 1-2 horsepower for push mowers. Because they don’t need much power the compression ratio is lower on these engines. Most lawn mower engines are between 6:1 and 8:1 while most motorcycle engines are 9:1 to 10.5:1 with competition and custom engines going even higher, but these require higher octane fuel.

The second benefit to electric motors running cooler than gas engines is that there are no hot exhaust or cooling fins to get burnt on. When I was around 12 I was still riding my Z50 and I was riding one day and a car turned down the alley and ran me off of the road into my neighbor’s ditch. When I fell my pants got caught in the chain and torn up past the knee, then the exhaust came down on my calf and let me tell you, exhaust burns are not fun.

It is worth noting that these electric motors do still produce heat, just not as much and it doesn’t radiate as much. The heat from an electric mini bike will usually come from the motor itself, which can get too hot to touch but should be hidden away, and from the cables connecting the motor to the batteries. The motors will sometimes have cooling fins which will cause the heat to radiate away from the motor more efficiently, but most do not. Most of the time the heat a motor produces is not enough to damage it, so the manufacturers simply hide the motor behind some body panels to keep anyone from touching it and getting burnt. Same thing goes for the battery cables. They will burn you if you touch them after they have been under load. This is not up for debate. The difference between this and, say an exhaust, is that the exhaust is exposed, whereas the cables are hidden.

So, which one takes the crown here? I have to give it to electric. When it comes to heat, and the safety concerns that surround it, electric wins out. An electric minibike will simply not produce the same amount of heat as a gas engine and the heat it does produce is contained to areas where there is little to no risk of anyone getting burnt unless they are working on it. If this is the case, then it should be allowed to cool first anyway. So while you may burn yourself on a hot wire while you are working on your kid’s minibike, they are not going to get burnt by a hot engine or exhaust.

Is an electric mini motorcycle worth it compared to gas minibikes?

mini-electric-bike-razor-725

Are they worth it? That’s up to you to decide, but if you live in an area where police or neighbors would have a problem with a gas powered minibike, or you want something, but can’t afford a gas powered bike then these electric minibikes are a solid alternative. While purists may demonize electric minibikes they do have their place. Personally, I would take an electric bike over no bike any day.

Conclusion

Should you buy your kids a mini bike? I say yes, everyone should have a motorcycle growing up, but it’s not my call. Ultimately it is your decision whether or not to get your child a minibike, but if you consider what we have discussed in this article you can make a well informed, safe decision and provide your kids with something they will cherish for a lifetime. If you’re looking what kind of mini bike would be best for you, check out our best mini bikes article. If you prefer something else after reading this, check out our best quads guide as well as our best go karts guide.

What are you waiting for? Get out there and ride.

2 thoughts on “Mini Motorcycles, Their Types, Uses, and Limitations

    • First check and make sure there is no packing material or anything blocking airflow to the fins. It’s possible there is some tucked up in there to keep them from getting damaged in transit. The second thing I would check is the oil level. The motor oil plays an important role in keeping air cooled bikes at their proper temperature. If these are both fine check your spark plugs. They should not be ashy. If they are this means the engine is running lean and you will need to swap some larger jets into your carburetor.

      That said, I can’t diagnose everything over the internet, and if it still runs hot it is a good idea to have a mechanic have a look at it. Best of luck and enjoy your Tao Tao db t1004 110cc!

Leave a Comment