Loading... Please wait...
  • +66 (0)38 422.208.
  • Gift Certificates
  • My Account 



Hover over image to zoom

  • 164cc, PGM-FI Controller, 31mm Throttle Body, Twin-Spark Spark Plug, this kit has it all!!...
RRP: $724.66
$665.38 (You save $59.28)
4,000.00 Grams
Usually ships in 1 week
Free Shipping
Minimum Purchase:
1 unit(s)

 Product Description

free-shipping-worldwide-new-big-.png164 LIGHT BORE ULTRA POWER PACK (PCX125 FIRST GENERATION / 13MM PISTON PIN) 

● The 164 Light Bore ULTRA kit is the perfect kit for anyone looking for an amazing kit with the emphasis clearly on the power side…

This ULTRA kit has been developed to give you total control and to remove the stock RPM limiter entirely to make maximum performance possible. We recommend installing a wideband AFR meter, and a tachometer to make perfect tuning possible.

The name "Light Bore" is a reference to the fact that this entire kit has been developed to be used in combination with the stock 125cc cylinder head. 

The 164cc cylinder in the Light Bore ULTRA kit has been designed with the 125 water cooling holes pattern.

The design from the special 60mm light bore piston make a seamless install possible with the stock 125 cylinder head. (Keep in mind that a 150 cylinder head cannot be installed on this type of cylinder...).

All parts in this kit are very well balanced to be installed on your first generation PCX125 and all parts in the Light bore ULTRA kit are easy to install.
Normal motorcycle / scooter mechanical skills are required, and with the deeper valve pockets in the 60mm piston we recommend to set the valve clearance at 0.05mm intake valve / 0.08mm exhaust valve.

We recommend to modify the stock exhaust, or to install the Silent Sport exhaust from our Takegawa colleagues in combination with this kit to get the full power potential of the kit.



● The Yuminashi R&D programmed the map from the controller based on the results on both, on the Dyno and on the road tests, so the settings should be pretty close to what you need. We strongly recommend not to change the ignition timing since Yuminashi pushed it as far as it's safe to use, you don't need to try to push it more on that side, an overheating engine will be the only result of that with a serious chance on engine knock.

To read more about the possibilities with the PGM-FI Controller we would like to invite you to take a look with clicking on this link.
If you want to get your tune absolutely right, then we recommend to install a Wideband O2 Gauge like the Innovate MTX-L gauge, like you can see in the picture below on the PCX125 V1 from Sergio Vasconcelos in Portugal, who has also an additionally RPM meter build in in the dashboard, which are available in some aftermarket dashboards on the market for PCX125/150 first generation.

The Air Fuel Ratio (AFR) we recommend with WOT (Wide Open Throttle) is 12.3AFR. As you can see below the AFR is 12.4AFR which is almost spot on based on our recommendation of 13.2AFR.

pcx125-sergio-vasconcelos-yuminashi.png        pcx125-sergio-vasconcelos-afr-yuminashi.png 

● The 31mm throttle body is 25% larger compared to the stock PCX125 throttle body, and the reason why this much larger throttle body is included in the kit is because the stock throttle body is a serious restriction for the much larger amount of air sucked in by the 164cc big bore piston. Removing the stock throttle body and replacing it by the 31mm throttle body allows the engine to suck as much air in as possible, and opens the full potential of your engine in combination with the big bore kit.

The larger 31mm throttle body with the 2018 stainless throttle cable bracket is plug and play and allows all sensors to be installed from your stock PCX125 throttle body. A new special O-ring comes with the kit to make the perfect seal possible...

16410-kwn-031-new-31mm-body-upgrade-sh-pcx-.png 16410-kwn-031-new-31mm-body-upgrade-sh-pcx-p02.png

 ● The 6-Holes A-Type High Performance injector is included in the kit for the simple reason that sucking more air in the engine with a much larger piston and a 25% larger throttle body requires more fuel to keep the perfect balance between air and fuel. 
This is important of course for the performance of the engine, but also for the reliability since a lean running engine would have overheating issues. Selecting the right injector is really important and with including the right injector in the kit you can be ensured your engine gets the fuel it needs to get.

**With the controller you can adjust the fuel amount to get your Air Fuel Ratio based on your location, humidity and altitude really spot on. Barometric pressure is highest at sea level and decreases with altitude. A reduction in atmospheric pressure requires leaning the fuel mixture.  


 ● The 31mm A-Type Manifold Set is included in the kit to make the install from the injector and the throttle body a truly plug and play experience. The stock injector joint from the PCX125 can be installed on this manifold and injector to connect your fuel hose.


  ● The 1.6 High Pressure Cap which comes with the set is to make sure your cooling system can control the extra power and doesn't open premature at 0.9 bar. All cool details about the protection from this cap can be found over there (recommend to read!). 


● The 164cc Light Bore Piston is made just like all other Yuminashi pistons from AA-Grade aluminium and finished with a black molybdenum coating on the sides of the piston. The piston from this 164cc light bore kit has been developed to work in combination with the stock 125cc cylinder head and valves, hence the name Light Bore Kit and Light Bore Piston. 

The valve pockets in the piston are machined deeper compared to stock, and allow a 0.05mm IN / 0.08mm EX valve clearance. 

● The high grade Yuminashi piston rings are developed and produced by very strict Japanese standards and all rings are treated with a hard chromium plating layer (Cr). All details about the piston rings can be found over here.


● The YUMINASHI Billet CNC X250RR Camshaft Kit comes also with the ULTRA kit, and this cam is the hot ticket for getting the most out of your PCX125 V1 engine.

This Yuminashi camshaft is designed in conjunction with our racing efforts, and in turn the design gets passed down to our customers for the best power gains.

Yuminashi R&D designed this camshaft to be used in combination with the stock 125cc valves, with an increased lift and duration to produce a potent curve with solid torque to red-line.
This means when you whack open the throttle out of a corner, you'll get a nice hit off the bottom all the way to the top!

All Yuminashi camshafts come standard with high-speed NACHI JAPAN C3 bearings to meet our standards concerning durability and reliability.

These high-end bearings can run exteme high RPM's, where the C3 stands for an optimal clearence with less friction at operating temperature.

The 2 special tappet adjusting bolts come with the camshaft in the kit because with the high lift of the camshaft it's not possible to use the stock tappet adjust screws.

**The valve clearance is 0.05mm IN / 0.08mm EX.


 ● The Progressive Double Valve Spring Conversion Set comes with the ULTRA Light Bore Kit for the power aspect, but also for the safety aspect since your engine has no RPM limiter anymore once the PMF-FI Controller is installed, and these double valve springs eliminate the chance on floating valves at high RPM entirely.

This kit includes 2 outer valve springs, 2 inner valve springs and 2 lighter as stock steel 5mm valve retainers to make a complete conversion from the stock single valve springs in to a double valve spring setup possible…


● The CR10EK Nickel Multi-Ground spark plugs have been tested in combination with the Yuminashi 164cc light bore kits, and the results are a cooler running engine with improved combustion, and clearly less sensitive for engine knock.

Multi-Ground Electrodes Improve Ignition Capabilities and Are Less Sensitive to Increased Voltage Requirements Due to Gap Growth.


● The 164cc Flat Deck Cylinder is pure racing DNA from the YUMINASHI PRO-SERIES.

The Flat Deck cylinder has larger water/coolant capacity, and is developed by the Yuminashi R&D to have a cooler running engine.

With the flat deck design you are able to run higher compression ratios without the fear of blowing head gaskets. A very hard cylinder sleeve has been installed which comes directly from the Yuminashi racing series engines to avoid ovalisation, oil leaks and compression loss!...

This specific cylinder block 12100-KWN-600X has been prepared to be plug & play ready for the first generation PCX125 crankcases. The crankcase bore is smaller from the first generation PCX125 compared to the eSP PCX125's, so the cylinder has been developed in such a way to make a plug & play install possible. 

This cylinder block comes also with the 2 pins to connect the stock ignition coil bracket on the cylinder, which is also unique for the first generation PCX and with a 125cc mark on the cylinder so that there isn't any difference compared to stock once the cylinder is installed on the engine.


● The special copper 0.3mm gasket set is made to make a perfect fit with the stock 125cc head in combination with a 60mm bore on the first generation PCX125 high compression engine (164cc kit). These copper gaskets come with the kit to make sure your engine makes the perfect seal. (Click the image below for more information)


 ● The large diameter Big Tube Air Intake Set for the 31mm throttle body which comes with the kit make sure your engine get's the air it needs to make the most power out of it, (more information and pictures can be found over here).

Keep in mind that the diameter of the hole in the stock PCX125 air filter box will need to be modified, and the length from the Big Tube Air Intake will have to be shortened based on your needs. 



● The Torque Control Variator Set is the cherry on the cake in the package which will improve both, acceleration and top speed. 
The 8 gram roller weights are included in the set.



 Free worldwide shipping with DHL Express is included in the price quotation!..
(Exception for Russia, Portugal, Brazil, Canary Island and French Polynesia, they will be served with free shipping by the Express Postal service)




WW125A   (NC125S)                (2010): Thailand
WW125SA (NC125S/NC125D) (2010): Thailand
WW125EX2A (JF2811)   (2010/2011): Europe / Australia / Belgium / France / Korea / Nippon / Polska / United Kingdom
WW125EX2B                           (2011): Turkey / Vietnam / Korea
WW125EX2A (JF28)                (2012): Europe / Belgium / Polska

Vendors Other Products

You Recently Viewed...

What's News


Copyright 2018 YUMINASHI DIRECT SALES. All Rights Reserved.
Sitemap | Bigcommerce Premium Themes by PSDCenter

Click the button below to add the 164 LIGHT BORE ULTRA POWER PACK (PCX125 FIRST GENERATION) to your wish list.