![The most powerful Dax 125 engine is born! How does the SP Takegawa 4-valve head perform? [Video: Moto Champ TV]](https://motopeek.com/wp-content/uploads/2025/09/1701-1761127700160.jpg)
Super Head 4V+R Combo Kit released by SP Takegawa.
Special Parts Takegawa (hereafter referred to as SP Takegawa) has finally released the Super Head 4V+R for the Dax 125 (JB04/06). SP Takegawa has released a number of bore-up kits and engine tuning parts, but the Super Head 4V+R is a full-spec model that can turn your engine into the most powerful one, so to speak. What’s more, with the combo kit you can increase the displacement up to 145cc. The contents of this fascinating kit were introduced in an episode of Moto Champ TV, which distributes free videos on YouTube, titled ” SP Takegawa’s 4-valve head turns your Dax 125 into a fierce dog! ” We’ve put together a digest of the video again this time.
The most powerful Dax 125 was born.
This time, instead of assembling the parts, we are showcasing a demo car from Special Parts Takegawa that is equipped with a Super Head 4V+R combo kit. Not only is the engine equipped, but also a muffler and oil cooler, and it has been customized so that you can enjoy the strongest head to the fullest.
The words SUPERHEAD 4VALVE are cast into the head.
On the left side of the cylinder head, it is proudly inscribed “SPECIAL PARTS TAKEGAWA SUPERHEAD 4VALVE,” proving that this is an engine with the strongest specs. This alone is sure to make anyone who sees it say “!” Let’s take a look at the contents of the kit below.
What is included in the Super Head 4V+R Combo Kit?
The kit’s cylinder head is a special item as it is a 4-valve head.
The main feature of this kit is the 4-valve head, and naturally the cylinder head is specially designed. Kits for the same engines have already been released for the Monkey 125, Grom, and CT125 Hunter Cub, but this time it is a kit specifically for the Dax 125.
Looking at the combustion chamber side, we can see that it has a four-valve configuration with two intake and two exhaust valves.
Looking at the combustion chamber side of the cylinder head (the surface that meets the piston), you can see that it has four valves. In addition to improving intake and exhaust efficiency compared to conventional two-valve engines, the engine is committed to achieving high output, with the spark plugs positioned in the center of the combustion chamber. The intake valves are 21.5mm and the exhaust valves are 18.5mm.
Naturally, the piston is also a special part, and the recess shape is noteworthy.
The piston body is precision-engineered and machined from cast aluminum. It is lightweight yet strong and rigid. Combined with the head, it achieves an ideal combustion chamber shape, while providing ample valve clearance for a high compression ratio.
The camshaft is also a special part.
When you think of a 4-valve head, you probably think of DOHC, but this kit converts it to a 4-valve head while still maintaining the SOHC configuration. To achieve this, the camshaft is supported on both ends with ball bearings, and the journals are designed to reduce wear resistance. An auto-decompression mechanism is used to reduce the strain on the transmission and during kickstarts.
The big throttle body is an existing product, but the intake manifold is a special product.
The intake system is fitted with a big throttle body, which is a φ34mm specification and is the same part as the Super Head 4V+R. However, since it is for the Super Head, the intake manifold is specially designed. The injectors installed are also large-capacity G1 types. The air cleaner is also a power filter specification.
The main reason for the release of the kit for the Dax 125 was the completion of the dedicated FI-Con Type X.
FI CON Type X is an injection controller that can change the fuel mixture by connecting it to the original ECU with a coupler. It is no exaggeration to say that the Super Head 4V+R Combo Kit is an indispensable part of the FI CON Type X, which was commercialized thanks to the progress made in its development. However, Type X requires a compatible computer or smartphone, and you will need to download software and apps to set it up.
A high compression piston kit is also available to keep the displacement below 125cc.
The combo kit introduced here has a displacement of 145cc, which requires registration as a light two-wheel vehicle. If you want to enjoy it as a Class 2 moped, you can also aim for high power with a high compression piston kit. This kit also requires the use of the FICON Type X, which shows how urgently the development of an FICON was needed.
Test drive the Super Head 4V+R
When you take a test drive, you’ll be blown away by the overwhelming acceleration!
This time, we test rode a demo model of a Dax 125 fitted with the Super Head 4V+R combo kit at SP Takegawa. Its performance was so impressive that it was easy to see the tester’s amazement. It accelerates with racer-like response, power, and torque, so much so that for a moment you forget that it’s a Dax 125. The engine power is completely different from that of the stock Dax 125, so don’t expect a smooth ride. It has been transformed into a completely high-speed machine. We should also point out that the tester’s voice is unclear while driving in this video, although it’s unclear whether this is due to the volume coming from the muffler or the engine itself. That’s how powerful the engine is.
During the test drive, the tachometer steadily reached over 10,000 RPM.
When I tried full throttle on a road with little traffic, I realized how powerful it was, with the front end easily lifting off the ground unless I held it down with both arms. What’s more, the tachometer needle still wanted to rev beyond 10,000 RPM, and there was no sign of a drop in power. This was truly impressive, so I recommend watching the video to experience its power for yourself.
Parts required other than the kit
Since the power increase will be tremendous, I would like to install a reinforced clutch and oil pump in addition to the kit.
Because it will be an incredibly powerful engine, you can enjoy it with peace of mind by incorporating reinforced parts that are not included in the kit. In particular, strengthening the clutch springs and oil pump is essential, and we recommend installing them at the same time as the kit.
As the displacement increases, a muffler with good exhaust is also required.
Since the displacement has been increased to 145cc, the exhaust efficiency of the stock muffler is obviously insufficient. Furthermore, by using a muffler with better exhaust, you can eliminate clogging and bring out the original power. SP Takegawa has a lineup of various mufflers for the Dax 125, so you can choose one according to your preferred style.
It easily revs up to over 10,000 rpm, so you’ll want a multimeter and oil temperature gauge.
With its overwhelming acceleration and engine that can easily reach over 10,000 rpm, it goes without saying that a tachometer with a suitable scale is necessary. SP Takegawa’s Super Multi TFT meter has an analog tachometer and digital displays for the speedometer and other indicators, making it easy to read. Also, if you want to enjoy revving the engine to your heart’s content, oil temperature management is essential. It’s also a good idea to equip it with a compact LED thermometer.
If you’re going to rev it up, you’ll also need an oil cooler.
Last but not least, it’s a good idea to equip your bike with an oil cooler. The recommended oil change cycle is every 1000 km, so oil management must be even more thorough than with a normal bike. At the same time, installing an oil cooler is also important for engine management as it helps minimize oil deterioration.
