The Best Selling Bore Up Kit for 4 Mini’s Standard Customization! [Advantage & Disadvantage]

Parts & Gear Reviews
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I'm Kotaro, a Webike staff member, and I'm a hidden Cub master in the company. I have a Cub, but it's long-distance commuting to work, so I end up commuting on a bigger motorcycle.

I also like to ride my Cub on the road, so I'm wondering which bore up kit I should install to make it a fast commuter. I'll be explaining the bore up and showing you the best selling bore up kits for each 4mini motorcycle model!

What is bore up?

To explain it very briefly, it is to increase the displacement by replacing the cylinder or widening the bore and replacing the piston as well! The idea is to widen the cylinder because the displacement is the inner diameter of the cylinder x the height that the piston goes up and down. By increasing the displacement, you can increase power and torque. The most common way to bore up is to buy a kit that contains everything you need, including cylinders and pistons.

Advantages and Disadvantages of Bore Up

The primary advantage is that it makes your motorcycle faster by increasing power and torque.


For a moped with 50cc or more
- No more 30km/h limit.
- No more two-step right turns.

For a moped with a capacity of 125 cc or more
- Use of expressways and other motorways will become possible.


- The life of the vehicle and engine will be shortened due to the increased load on each part of the vehicle compared to the manufacturer's design.

- A motorcycle license corresponding to the increased displacement will be required.

- Higher taxes (margin of error)
- There will be other parts required for setting other than the bore up kit.
-  As a result, I'm getting more addicted to the swamp.

Not sure if you can do it yourself? I have a good manual!

If you are new to bore up and don't know how to do it, Kitaco has a manual for you!
Detailed explanation with illustrations on how to assemble the bore up kit for 6v to 12v models, centrifugal clutch models to manual clutch models. Two types are lined up, horizontal type for Cub and Monkey, and vertical type for Ape and XR! Even if the manufacturer or the age changes, the basic structure of the engine is the same, so it is possible to buy it as a reference book.

KITACO: Catalogue (MONKEY SERIES ENGINE) Vol.4 for MONKEY/Super CUB Series Horizontal Engine

KITACO: Catalogue Cylinder Head, Cylinder & Piston for APE Series Vertical Engine

Are you tempted to upgrade your bore? Here's a kit I recommend by model!

Speaking of bores up, it's the Honda 4mini horizontal and vertical engines. There are so many different types of bore up kits available from different companies that even Webike's purchasing staff can't keep track of them all. I'm going to show you one of our most popular kits that is always on the top of our sales list!

Horizontal type of Cub and Monkey

KITACO: Light bore up

Very good cost performance bore up kit! You can use the stock cylinder head as it is, so the cost is reasonable. Also, it uses a steel cylinder, which is rare for an external bore up kit, so durability is perfect! It can be used with the stock carburetor, so it is recommended as an introduction to bore up.

SHIFT UP: Monkey 88cc High Revolution Bore Up Kit (with High Range Camshaft) for 12V

The standard bore up for a horizontal engine is the 88cc. This kit comes with a special cylinder head and a special high camshaft. One of the fun parts is upgrading it, but it's a lot cheaper to build a full kit from scratch!

SP Takegawa: 17R Stage E Bore Up Kit 106cc (SCUT Cylinder) SCUT

I don't want to explain in detail, but the limit of the horizontal engine is 88cc when it is bored up under the waist without machining. If you want to increase the displacement, you have to shave the crankcase and install a long stroke crank. However, SP Takegawa's Scut Cylinder achieves the dream of over 100cc without any processing by eliminating the scut of the cylinder!

Ape and XR series vertical type

KITACO: LIGHT Bore Up Kit [Light Bore Up Kit] (82cc)

This is the vertical version of Kitaco's LIGHT Bore Up Kit that we introduced in the horizontal engine section! You can use the stock cylinder head as it is, so the cost is also reasonable.

DAYTONA: Hyper Bore Up Kit (Compatible with stock air cleaner 80cc)

This kit from Daytona is recommended for those who want to go from a stock 50cc to a complete kit. With everything from a high camshaft to a standard PC20 carburetor, it's under 50,000 yen including tax! That's a great deal! The point that a normal air chest box can be used is also GOOD.

SHIFT UP: 100cc to 115cc Bore Up Kit

Simple bore up kit for stock cylinder head. It even has an outlet for the oil cooler!

YOSHIMURA:Yoshimura Head (115cc) Kit

Yoshimura has a strong image of the exhaust system, but there is also bore up kit. Forged aluminum pistons are used to further increase the compression ratio to 11.5:1 to achieve a significant increase in power output in the entire RPM range! By using an all-aluminum plated cylinder, it is both durable and lightweight.

Cub 110/Cross Cub 110

SP Takegawa: Hyper S-stage Bore Up Kit 125cc (Big Throttle Body Spec)

Full kit with big throttle, high camshaft, and injection controller. It's bored up to 124cc so you can still ride with the pink numbers! It's been 7 years since the Cross Cub was introduced. Isn't it time for a refreshing power upgrade?



This kit includes a highly efficient ported head with big valves and a crank. Since it is 181cc, it is possible to drive on the expressway. Grom on the expressway! It's perfect to surprise people around you!

When riding on public roads, you will need to change your registration, license, insurance and other conditions because you exceed the 125cc limit.

Monkey 125

SP Takegawa: S-stage Bore Up Kit 181cc (without camshaft)

This kit is recommended for the next step after installing the Hi-Camshaft! By installing the FI Controller at the same time, a torque-filled output characteristic different from the stock can be achieved.

When riding on public roads, you will need to change the conditions of your registration, license, insurance, etc. because you exceed the 125cc limit.

SP Takegawa: Super Head 4V+R Bore Up Kit 181cc

The 181cc cylinder is set in the original SOHC 4 valve head that boasts the highest class of intake and exhaust efficiency. How about that dream 4 valve conversion!

When riding on public roads, you will need to change your registration, license, insurance and other conditions because you exceed the 125cc limit.

CT125 Hunter Cub

SP Takegawa: S-Stage Alpha Bore Up Kit 181cc

The CT125 Hunter Cub was also named Japan's Bike of the Year for 2020. For the adventurous, like driving on rough dirt roads or loading up on camping trips! Let's get some moar power!

When riding on public roads, you will need to change your registration, license, insurance and other conditions because you exceed the 125cc limit.

I have a scooter too! Address V125

SP Takegawa: Hyper S Stage Alpha Bore Up Kit 161cc

This kit has been on the market for many years, but is still very popular. Are you buying this product to win the commuter battle that is waged across Japan every morning? I don't want to lose in the Signal Dash! What do you think?

When riding on public roads, you will need to change your registration, license, insurance and other conditions because you exceed the 125cc limit.

Extra! Zephyr 400

POSH Faith: Bore Up Kit

I know I've only been showing you the small displacement kits, but here's another one! By re-sleeveing and boring, the cc has been increased from 400 cc to 510 cc.

When driving on public roads, you need to change the conditions of registration, license, insurance, etc. because you exceed 400cc.

Let's get stuck in the 4mini swamp!

Some of the products are in stock, so if you can't go out during the holiday, it might be a good idea to relax and bore up at home. If the kit of your motorcycle was not in my list which I introduced, click the button below to find it.

See Accessories of KITACO
See Accessories of SP TAKEGAWA
See Accessories of YOSHIMURA
See HONDA Moto Index Page
See Accessories for HONDA CROSS CUB (CC110)
See Accessories for HONDA CT125 Hunter Cub
See Accessories for HONDA MSX125 (GROM)
See Accessories for HONDA Monkey 125

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