Midbike / Superbike Information : Lots of X18 Help Here

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Midbike / Superbike Information : Lots of X18 Help Here
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If you are looking at midbikes, also called superbikes, this may be very helpful to you. This is primarily written about the X18, one of the most popular midbikes out there, but the information applies to many other bikes.

Comparing and Choosing the X18

People commonly ask about the X18, compared to other bikes when they are ready to purchase a midbike. Most of the X series midbikes are basicly the same, with slight changes from model to model. Generally, they pick up some positive changes from their predeccessors. In the following paragraphs, I will outline some of the features of this bike. In order to make an educated buy, I would suggest you look for similar information on the other bikes that you are interested in.

4 Speed Manual Clutch 110 (107cc) Engine : Other bikes offer 110s, but not all of them are available with a manual clutch. The manual clutch will require a little more practice to drive, if you have never driven a manual clutch motorcycle or pocketbike before. It will also deliver more power than the automatic and semi-automatic (automatic clutch). It gives you the
ability to release the clutch at higher rpms to help with faster take-offs and wheelies.

EPA Approved : The newest X18s boast EPA approval. If you are going to try and register the X18, it can be considered a pro for the X18. There are other requirements, depending on state and local laws to register a vehicle, so don't assume it will automaticly be street legal. In some states, it doesn't matter what approval you get, they will not register pocketbikes. It's up to you to know your local laws. If you do not wish to ride the X18 on the street, I wouldn't take the EPA approval into consideration, when comparing the X18 to other bikes. The only thing you are really getting, as opposed to non-EPA approved bikes, is a PCV system. PCV stands for positive crankcase ventilation. A hose running from the crankcase vent to the intake manifold
allows blow-by and crankcase gases to be burned. This helps reduce hydrocarbons entering the atmosphere, but should show no performance increase.

Stock Speed : One of the selling points of the X18 is it's top speed, as advertised. There have been reports ranging from 45 to 65mph stock. Many of the claims are completely false. The 63mph video, that many sites use, is advertised as a stock, "out of the box", X18. If anyone can tell you that's a lie, it's me. Said video, happens to be mine. "Out of the box" that bike ran
48mph. In that video, the bike had been modified, and I clearly posted that with the video. Most sellers choose to leave that information out when they use it. Realisticly expect 45-50mph from a stock X18. They may change gearing by manufacturer, and some may go faster, but don't assume you will go over 60mph right out of the box.

Reliability : I have noticed a few posts, asking if the X18 is reliable. The X18 is about as reliable as any other 4 stroke Xseries bike, from my experience. It has it's flaws, but they all do. Proper maintenance is essential. I don't know what it comes out to in mileage, but I know you can put many many hours of riding on a properly maintained bike.

Size : A number of people have asked if they are too big for the X18. I am 6 feet 3 inches tall and 280 pounds, and have no problems on the X18.

X18 R/Nitro : Another common misconception about the X18 is that the R and Nitro models are faster. In reality, they are just named different, and have some R/R-Nitro stickers on them. If you like the way one of those models looks, and the price is right, give it a shot. I wouldn't suggest paying much more for one though, unless you really want those decals.

You Read, You Reasearched, You Ordered An X18... Now What?

Once you get your new X18, there are some things you should do before you ride.

-If your X18 was shipped, unpack it, check for damage, and assemble it.

-Drain the shipping oil from the engine, and replace it with petroleum based motorcycle oil.

-Check the pressure in both tires. Some bikes have a plate on the body or frame that tells the recommended pressure. Most tires also have a Max PSI on the sidewall. Most riders use around 30-32psi.

-Check the essential nuts and bolts, and Loctite them if you desire. Chinese manufacturers have a tendency to overlook things, and you don't want a wheel falling off while you ride. Check the handlebars, wheels, brakes, engine mounts, etc...

-Find the fuse holder on your bike, and be sure there is a good fuse in it. Some bikes are shipped without the fuse installed.

-Put a little bit of premium unleaded fuel in the tank. Take a look at the fuel line going from the tank to the filter to the carburetor. Make sure no gas is leaking. If it is, secure the clamps, or replace hoses, as necessary. If your bike is leak free, fill it up.

-Familiarize yourself with the bike. Sit on the bike. The left lever on the handlebar is your clutch lever. The right lever is your front brake. The lever by your right foot is the rear brake. The shifter is near your left foot.

-Insert the key into the ignition, and turn it to the on position. Your gear indicator should read "0" meaning the bike is in Neutral. Hold the clutch lever, set the choke, and press the electric start button. Verify that the bike is in neutral, and release the clutch.

-Roll the bike forward slowly with your legs. Verify that the front and rear brakes work.

-Try your headlight, turn signals, tail light, horn, etc...

-Put on your safety gear (helmet, pads, gloves, leathers).

-Hold the clutch in and shift through the gears to familiarize yourself with the shift pattern.

-Hold in the clutch and shift into first gear (1). Slowly release the clutch and ease into the throttle. Do this a a few times, so you can get used to the clutch.

If everything is working properly, you are suited up in your safety gear, and you are familiar with the clutch and other controls, you should be ready to take your first ride. Remember to take it easy at first. Once you get used to the bike, you can gradually speed up. Be safe.


Some bikes come with restrictors and some do not. Restrictors are most commonly devices that restrict the carburetor from opening all the way.


Break-in is a topic that provokes some discussion. Some people believe that to properly break-in the bike, you should be easy on it for about 3 tanks of fuel, or leave the restrictors (if equipped) in place. Others believe the best method is to run it like you will want to run it (if you plan to run it hard, break it in hard). I have used both methods, and both worked fine for me. Choose the one that you feel is right for you.


There are a few things you should do on a regular basis to keep your bike in good working order. Below is a list of things you should be certain to do.

Oil Change

I prefer to change the oil at least once a month, more often if I ride more than usual. Oil change intervals is another topic with varied opinions. One thing that you can be ceratin of, is that you cannot change your oil too often.

You also need to choose a quality motorcycle oil for your bike. Regular automotive engine oil is not recommended. Motorcycle oils are formulated to work with wet clutches, like these bikes have. Automotive oil can cause the clutches to slip, resulting in a severe loss of power in some cases. There are many different motorcycle oils available in petroleum based, and fully synthetic varieties. Be sure to use petroleum-based oil for the first few tanks, no matter what type of oil you plan to run afterwards. 10w30 and 10w40 synthetic motorcylce oils are the most popular choices for this style of engine.

Air Filter

You should check your air filter every few oil changes. If it is dirty or airflow appears to be obstructed, it should be replaced.

Spark Plug

I like to pull the spark plug out at every oil change. This allows me to read, re-gap, and replace it, if necessary. If your plug is worn or fouled, replace it. If the plug is still in good condition, re-gap and re-install it. Do not gap iridium plugs, they come pre-gapped. Other plugs should be gapped to .024-.028 inches.


You should check the tension of your chain, and adjust it if necessary, every oil change or every other oil change.The chain should have some play in it, but not excessive play. Try to adjust the chain so that it will move about 1/2 inch up or down. Be sure to keep your chain lubricated with chain oil as well. If it becomes worn, replace it.

Carburetor and Throttle Assembly

The carburetor and throttle assembly should be checked every other oil change. Pull the throttle and make sure the carburetor is opening properly. Look for excess dirt and grease in the carburetor, and clean with carb cleaner if needed. Make sure your throttle cable isn't frayed. Check the screws that hold the bowl onto the carburetor. Adjust if necessary.


Check your tire pressure at every oil change, and any time you can see or feel a difference in the tires. Unless you are using a racing slick, replace the tires when your tread wears down.


Take a look at your brakes every time you change the oil. Make sure the levers are firm. Look at the brake pads, and make sure they are not down to the metal or close to it. Push the bike and hold the brakes. Most bikes will drag the tire. Replace, bleed, or adjust your brakes as necessary.

Fuel Filter

Have a look at the fuel filter often, and make sure it isnt dirty or clogged. Replace if needed.

Screws, Nuts, Bolts

Check over the essential nuts, bolts, and screws on a regular basis. Use loctite blue if bolts or screws become a recurring problem. If you are really motivated, take a bunch of your fasteners to a local harware store. Replace the stock fasteners with hardened, stainless, or any quality pieces you prefer. Some local stores even carry a selection of chrome fasteners.


You should check the bearings from time to time. Spin your wheels to assure they operate smoothly. Turn your handlebars to check for play. If they turn too easily, you may need to tighten the forks, or check/replace the bearings inside.


Be sure to keep your battery charged at all times. Chargers, such as the Battery Tender, are widely available. The battery tender, and many other trickle chargers, will not overcharge your battery, and have lights to tell you when the battery is fully charged.

I Wanna Go Faster, How?

There are quite a few options for increasing performance. You can change gearing, engine upgrades, a larger engine, and more. The trick is to decide what you want, and what your mechanical ability will allow you to do.


Gearing for the X18 has became one of the most popular questions from riders. Everyone wants advice on what sprocket they should buy. Let me see if I can clarify a few things for you.

There are two sprockets that drive your bike. The front (counter) sprocket and the rear sprocket. The number of teeth on each of these sprockets determines a gear ratio. For example, say your bike has a 14 tooth front sprocket, and a 28 tooth rear sprocket. Divide the rear sprocket by the front sprocket to see a numerical gear ratio. 28 divided by 14 equals 2. Your gear ratio is 2.00:1.

O.K., now you're thinking, "that's nice, but what does it mean." If you have a gear ratio of 2.00:1, that tells you the counter sprocket must rotate 2 times to rotate the rear sprocket 1 time. The more your front sprocket rotates to rotate the rear sprocket 1 turn, the more take-off power you will have. This comes with a price though. Let's say when your engine is at it's maximum RPM, it can turn the counter sprocket at 1,000 RPM (Revolutions Per Minute). If it takes 2 revolutions of the counter sprocket to rotate the rear sprocket 1 time, it is only acheiving 500 RPM. Now, if you had a gear ratio of 1.00:1, the rear sprocket would be turning at 1000RPM.

Alright, so I can turn the tire at different speeds with different gears, so what? Let's say your tire will travel 10 inches every time it rotates. If you turn that tire at 500RPM, in one minute, it will revolve 500 times, and travel 5,000 inches. If you use the other gear ratio, and turn the tire at 1,000 RPM, it will travel 10,000 inches. The farther it travels in one minute, the faster it is going.

Hopefully you are not completely confused right now. If you are, there is still hope. Here it is in simple terms. The higher the gear ratio is, the more take-off power you will have, and less top speed. The lower the gear ratio is, the less take-off power, but the greater the top speed. More teeth up front
will lead to more top end oriented gearing. Less teeth up front is better for take-off power. More teeth in the rear will increase take-off. Less teeth in the rear with increase top end potential.

Here are some gear ratios you can achieve on your X18, and what sprockets will get you there. You have many options that will allow you to fine tune your bike to your needs.

3.17:1 - 12T front, 38T rear
2.71:1 - 14T front, 38T rear (stock setup on many X18s)
2.53:1 - 15T front, 38T rear
2.38:1 - 16T front, 38T rear
2.33:1 - 12T front, 28T rear
2.24:1 - 17T front, 38T rear
2.11:1 - 18T front, 38T rear
2.00:1 - 14T front, 28T rear
1.87:1 - 15T front, 28T rear
1.83:1 - 12T front, 22T rear
1.75:1 - 16T front, 28T rear
1.65:1 - 17T front, 28T rear
1.57:1 - 14T front, 22T rear
1.56:1 - 18T front, 28T rear
1.47:1 - 15T front, 22T rear
1.38:1 - 16T front, 22T rear
1.29:1 - 17T front, 22T rear
1.22:1 - 18T front, 22T rear

You should have a basic understanding of gear ratios by now. There are other important factors to consider before you run out and buy some sprockets. Gear ratios will give you an idea of what speed you are potentially capable of. The key word being potential. Your engine must have enough power to effectively use those gears, or you won't reach your full potential.

Here's an example, that may help you understand. A friend put a 14/22 setup on his 110cc manual X18, with a gutted muffler, hotter plug, and carb tuning. It reached 63mph (the bike in the video you see everywhere). At 63mph, the engine was not able to rev to its full potential with a 140 pound rider. I tried 14/22 (1.57:1) gearing on my 110cc semi-auto X12, with some minor mods. My bike topped out right around 52mph at a low RPM in 4th gear. I weigh 280 pounds. Obviously, my X12 did not have the power to pull a 280 pound rider to the gearings full potential. Even with a 140 pound rider on a little more powerful bike, the gearings full potential was not seen.

As the example illustrates, it is important to choose a gear ratio suitable to your bike and your needs. Gearing around 2.00:1 is an excellent choice for stock or nearly stock X18s and light to average weight riders (100-175 pounds). Of course, if you are a heavy rider like me, you may want to consider a numerically higher gear ratio. At 280 pounds, I would be better off with something like a 2.33:1 or 2.38:1 gearing. If your bike is more powerful, you may be able to go numerically lower and see good results. Try doing a search and looking at other peoples gearing/weight/mods/speeds to get more information on what gearing may work well for your needs.

I would also take ease of installation and cost into consideration when choosing sprockets. For example, if you decide you want 2.00:1 gearing, you would need a 28T rear sprocket and your stock 14T front. If you moved up to 2.11:1 gearing with an 18T front and stock 38T rear, you wouldnt see much differerence. Changing front sprockets tends to be cheaper and easier than swapping rear sprockets. Some more extreme sprocket changes also require adding or removing chain links. If price and difficulty are not issues to you, get whatever gearing you feel is the best. If you want to save time or money, you may want to search for information about similar gear ratios that may be cheaper or less difficult to install.

Engine Upgrades

There are tons of performance parts available for these 4 strokes. Some offer a great improvement, and some don't. Choosing your parts wisely will make the difference between money well spent and money wasted.

Iridium Spark Plug

Iridium plugs are a fairly inexpensive upgrade. They do not need to be gapped like other plugs. It is very unlikely that you will notice any increase in power. You may however have a bike that's easier to start, and more resistant to fouling. If you aren't on a tight budget, it might be worth the money.

Igntition Coil

Aftermarket ignition coils are intended to generate a stronger spark. Most of these engines will never need a stronger spark. You generally need a stronger spark when you drasticly increase cylinder pressure, from things such as higher compression, turbocharging, supercharging, etc... Under increased pressure, the spark can be blown out. Given the small gap of the spark plugs, unless your stock coil has seen better days, you should be fine until you build that high compression, cammed, nitrous, 114.


Aftermarket CDIs are advertised by some companies like they will turn your stock bike into some ground-pounding monster. I have never found this to be true. There are different styles of CDIs available. Some aftermarket CDIs only offer a change in the rev limit, others offer a timing advance, while others change the rev limit and the timing curve. I have installed CDIs that advance the timing with both positive and negative results. In one case, the bike acted as if the timing was too far advanced, and ran poorly. In other cases, the bikes seemed the same as stock, and with others there was a slight improvement. From my experience, I would save my money, at least until after some other mods.

Inner Rotor

Sellers claim the inner rotor kits will make a 4 stroke rev like a 2 stroke, because of the reduced rotating mass. I personally have no experience with one of these kits. I have been advised to save my money however. I was told they will rev a little higher, but they really aren't worth the price.

Exhaust Mods/Systems

Modifying or replacing the exhaust helps a little bit. You may or may not be able to feel the effects of exhuast modification and aftermarket exhausts on a stock engine. You can usually see more of a gain on modified big bore engines. One thing you can certainly do is hear the difference. If you like to hear your engine, and you aren't in an area where neighbors will object, exhaust mods are nice. You can do the mod in the article posted below for next to no money. You can also buy complete systems or buy a dirtbike muffler and weld it in place of the stock silencer/muffler.


I see a lot of people swapping carbs on stock bikes. Personally, I have never felt enough difference to make it worth the cost of the carburetor. Carb swaps can make a big difference on big bore engines, they also help on cammed engines a bit. If you really want to put a carb on your stock 110, 20mm carbs are a good choice. I have ran a 24mm carburetor on a 110, but I had to jet it down, and still didn't see any real improvement. 22mm carbs will usually work well on modified 110s. My suggestion would be to wait until you get a big bore kit or at least a cam, to upgrade your carburetor.


There are a few different intakes availabe for this engine. They make short, medium, and long runner intakes. There are aslo intakes that typically come with carbs to match up to them. If you really want the best bang for your buck, wait on an intake until you buy a carb, and then get an intake to match the size of the carb. You can also polish your stock intake, if you have the proper tools. I have always used a Dremel tool. To get all the way insdie the intake, you will need the flex shaft attachment. All you are trying to do while polishing the intake is smooth out the casting flaws. One other thing you can do, is assure that the intake matches up to the carb, heat spacer, head port, and gaskets. This will assure that the air/fuel mixture has a smooth clear path into the head.


Aftermarket heads are available for these engines. You can also port and polish your stock head. The race heads are much better than porting and polishing your stock head. The race heads offer larger valves, and improved ports. Porting and polishing your stock head will make a very slight difference, and if done wrong, can cause a loss of power. I would opt to buy a race head after or along with a big bore kit. It can make a difference on a stock engine, however it will do even more on a big bore setup with a cam.

If you choose to port and polish your stock head, I suggest you pull the head off of the engine. It can be done with the head intact, but you run the risk of metal shavings and dust causing damage to your engine. It is much easier to get the head clean with it off of the engine.

Once you have the head off, you are mainly just cleaning up the ports. You can slightly enlarge them, but I suggest only those of you that understand engines well do any of this. While you have the head off, make sure your intake port matches up to your intake. Before you re-assemble the engine, clean everything very well with carburetor cleaner or brake parts cleaner to assure no metal shavings or dust is left.

Head Breather Kit

Head breather kits are advertised to release pressure in the head, which will allegedly allow the engine to rev faster and make more horsepower. One problem with this claim, is that the crankcase pressure is already vented, rendering this kit a waste of your cash.

Big Bore Kit

Big bore kits are an excellent choice. They can transform your mild 107cc (referred to as 110cc) engine into a high compression 114cc. It does this using a domed 54mm piston, and over-bored 54mm cylinder. This kit, by far, made the biggest difference of any mod that I have done. I would highly recommend a big bore kit to anyone looking for more power. It does require removal of the head, sleeve, and piston, so it is important to have some mechanical ability. On some engines with the bottom mounted electric starter, clearancing some fins may be necessary. When combined with a race head, cam, and 24-26mm carb, you can basicly double the power of a stock 110.


Camshafts (cams) can change intake and exhaust valve lift, duration, and timing. These changes can allow more air and fuel in and out of the combustion chamber, change or extend the powerband, and in some cases, alter compression. These changes can allow your engine to rev higher, and create more power. There are two common sizes for camshafts in these engines. Be sure to measure your cam before ordering one. You should find it to be either 68mm or 73.6mm.

High Volume Oil Pump

A high volume oil pumps move more oil than standard oil pumps. This helps keep the upper end lubricated. If you have an oil cooler, it can also push oil through it more effectively. Installation of an oil pump requires drilling the oil passage as well as a lot of disassembly.

Oil Cooler

Oil coolers are designed to keep your engine temperatures lower, by cooling the oil. Cooler engine temperatures can aid in extending the life of your engine, as well as keeping it from losing horsepower due to heat. Oil coolers will work with stock engines, but I have found them much more effective after the addition of a high volume oil pump.

Engine Swap

Engine swaps are another option for getting more power. There are many 120cc and 125cc engines that will bolt in. If you are looking for more power, but don't wish to pull apart the engine, this may be a good choice for you. You can often find packages including a larger carb, cdi, clutch cable, and anything else you will need to swap engines. Of course, once you swap engines, you can add performance parts to it as well. Some people have built the 120 engines to exceed 160cc.

If this engine group cannot satisfy your needs or wants, you can also choose a different style of engine. This is very likely to require lots of welding and fabrication skills, and is not for the inexperienced.

I hope you have found this information useful. Use any infromation here at your own risk. I can't be held responsible if you choose a bike you don't like, or if you mess something up trying to modify it. This is merely a guide. Thanks for reading!

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