Special Parts Takegawa’s Super Head 4V+R Bore Up Kit 145cc for the CT125 Hunter Cub is priced at 171,600 yen (tax included).
Special Parts Takegawa has released the ultimate tuning kit for the Honda CT125 Hunter Cub. It’s called the “Super Head 4V+R Bore Up Kit 145cc.” We previously introduced the company’s “S Stage Alpha Bore Up Kit 145cc,” a bore up kit for the current CT125 Hunter Cub, in a test ride article . We noted that the 20cc increase in displacement provided power that matched the bike, but this time it’s a kit that can achieve even greater power increases. As with the last time, we’ve put together a digest of an episode posted on Moto Champ TV , a free video streaming service on YouTube, titled ” Spin it up to high RPMs! Test ride of the 145cc 4-valve head for the Hunter Cub! “
Super Head 4V+R Bore Up Kit Contents
A four-valve head with two intake and two exhaust valves.
First, let me explain what SP Takegawa’s Super Head is. A regular bore-up kit increases displacement by rearranging the cylinder and piston. SP Takegawa kits often come with a dedicated camshaft, but it’s common to use the original cylinder head as is. In contrast, the Super Head also replaces the cylinder head with a specially designed one. Looking at the combustion chamber, you can see that there are two intake and two exhaust valves, for a total of four valves.
Roller rocker arms with built-in bearings reduce wear resistance with the camshaft.
The rocker arm is what pushes and drives the valve. It is an important part that pushes the valve along the camshaft peak, and it has a built-in bearing just like the original. This allows for smooth operation and follows the cam profile from low to high RPM.
The pistons are specially designed to accommodate the four valve configuration.
With four valves, four recesses are required on the piston top. This means that the pistons in conventional two-valve bore-up kits cannot be used. Therefore, this kit comes with a special piston. The body is made from cast aluminum and is shaped using precise machining techniques. Because it is made from aluminum, it is lightweight and has a high rigidity.
The intake manifold is specially designed as the intake valve is 21.5mm.
The kit’s valve diameters are 21.5mm on the intake side and 18.5mm on the exhaust side, and the use of unequal valve springs allows for high-revving engines. This means that the engine’s ability to draw in the air-fuel mixture has been significantly improved, making it essential to have an intake manifold that can draw in more air. A dedicated intake manifold with the optimal port diameter is included.
The throttle body is also a large diameter type.
Naturally, not only the intake manifold but also the crucial throttle body is large in diameter. The combination of this big throttle body and large diameter intake manifold allows for smooth intake all the way to the combustion chamber.
Parts to be installed at the same time
At the same time as purchasing this kit, I would also like to change the muffler to improve exhaust flow.
The engine power will increase dramatically, but the kit only includes the intake parts. This is to allow you to match the muffler to your preference, but by using a muffler that has good exhaust, you will be able to feel the power increase even more.
Since it will be a higher rotation type than the original, I would like to use countermeasures on the crankshaft as well.
Since this engine produces explosive power at high revolutions, it’s best to protect the original crankshaft if possible. We recommend installing a crankshaft support adapter, which is also effective for durability. The work itself is relatively easy, as it only requires attaching the original part without replacing the crankshaft.
An oil cooler is also essential due to the increased heat.
Increasing engine power places stricter demands on the oil that lubricates the engine’s interior. While higher-grade oil is required, there are situations where this alone is not enough to counter the amount of heat generated. This is where an oil cooler comes in handy. The one pictured is specially designed to be easy to install, taking up little space and including special hoses.
The oil pump should also be upgraded to a stronger type.
It is more effective to improve the oil cooling capacity and also to review the lubrication flow rate itself. If you ride in a style that frequently uses high RPMs, you should review the oil flow rate all the more, and install a reinforced oil pump to address this.
We would also like to strengthen the cam chain tensioner to match the high-revving model.
When it comes to high-revving models, all sliding surfaces are subjected to more strain than the original. The same goes for the cam chain that drives the camshaft, so you should replace the cam chain tensioner with a reinforced one to address this issue.
What is the performance of the Super Head 4 Valve 145cc?
The Hunter Cub we test rode this time was a demo model provided by SP Takegawa. It was equipped not only with the Super Head 4V+R bore-up kit, but also with a generous selection of the reinforced parts we’ve introduced. This allows for a safe test ride. The video begins with the engine starting, and the first thing we hear is a crisp exhaust note. Opening the throttle also lets you hear the intake sound of the power filter, truly evoking the feeling of a tuned engine. Once we started driving, we could see that the effect was more than just the speed achieved by the increased displacement mentioned in our previous article . While the power was sufficient for a relatively large vehicle, the power of this Super Head was beyond impressive. The tachometer swung up to high rpm, as if it were exploding, and the momentum of the needle propelled the vehicle forward. It was so strong that we hesitated to call it a Cub; our tester was left speechless by the sharp acceleration.
It’s so powerful and effortlessly revs up to high rpms that it leaves you speechless.
The powerful performance when revved up to high speeds, along with the roaring intake and exhaust sounds that are incomparable to the stock, will get you excited whether you like it or not. However, it’s difficult to keep the top open continuously on a daily basis. There are times when the car in front is driving slowly or you’re driving on narrow alleys. Even in these situations, the demo car can be driven without stress. People tend to focus only on high speeds, but it doesn’t lose its ease of handling in practical ranges. For example, even when driving at a speed of around 40km/h in fourth gear, it drives smoothly without any sluggishness or knocking. This makes it fun to drive leisurely on peaceful country roads. Even though it’s a tuned engine, driving it normally isn’t stressful. You’ll be able to experience the benefits on a tour.
