● Click here to download the MSX/GROM 160 Ultimate Owners Manual.

●  This all-new 160cc Ultimate kit is really a great value for money kit where the Yuminashi R&D began from scratch with the goals to offer an entirely blue printed cylinder kit, to be able to increase the power of the kit, and to simplify tuning by eliminating guess work.

The ECU, camshaft, valves, springs, injector and all other parts have been optimized to work together as one set. As a result it eliminates the need for the customer to figure our ignition timing and AFR ratios by themselves. The result is the risk of engine damage caused by improper setup or incompatible parts is greatly reduced.

Yuminashi takes durability and reliability very serious, and that’s the reason why we as first company in the world include a standalone ECU system with overheat protection built in. We did this to protect your investment and to provide our customers with satisfying results in regards to performance.

The benefit of our new stand-alone ECU system is not only to be able to control the fueling accurately, but to eliminate conflicts with the stock ECU like have been seen in the past with some piggy back systems where engine damage could be the result.

The Overheating Control feature built in to our stand-alone ECU system monitors your engine temperature under all conditions. This system in your ECU is programmed to “give your engine a break” when it is being over stressed by reducing the ignition timing and by adjusting the Air Fuel Ratio. This is done to avoid engine damage, even if you are an extremely aggressive rider and are in Racing mode.

If your engine begins to run hot, the rider will feel it because your engine will temporarily have less power. The ECU has been programmed this way, but will return to normal once soon as the engine temperature has come down. If this occurs often, we recommend installation of an oil cooler. This is a great feature for anyone living in areas that have hot climates.


 The MSX/GROM 160 TOURING KIT includes:


  • New Stand Alone PGMA-FI Programable ECU unit with overheating control to replace the stock ECU unit
  • Big Bore 8-Hole Fuel Injector
  • New design SX290 8.2 high-lift camshaft
  • Special High-Lift Valves set (25,5/21mm) for STD 125cc head
  • Progressive 2-Valve Spring set 14751-K26-000
  • 2 Special High-Lift Retainers
  • 4 Special Valve Cotters for the High-Lift Retainers
  • Reinforced Clutch Spring set (6Pcs/set)
  • Spark Plug NGK CR9E
  • 160cc Cylinder (59mm bore)
  • 160cc Piston (59mm)
  • 160cc Piston Ring Set (59mm)
  • 160cc Gasket Set (Head gasket & Cylinder gasket)
  • 13mm Piston Pin
  • 2 Piston Clips (13mm)


PRODUCT CODE: 12103-K26-590AU

PRICE: 17.182THB (388€ / 535USD) Exclusive V.A.T.

YUMINASHI DIRECT SALES   (Please check in the link section if there is a official dealer nearby before you click and use this service...)


WORD OF WARNING!! If you order and install a 150cc or 160cc for your MSX/GROM without a ECU mapped by our company, then keep in mind that you need to check the AFR ratio and people who have a fuel injection controller with the possibility to adjust the pre-ignition must be aware that to much pre-ignition will blow a hole in your piston.

We don't take responsibility if you get carried away with the amount of pre-ignition, and the damage that occurred because of it.

We recommend to install the PLX DM-6 SM-AFR wideband combo (click here to see the details).

If you don't install a wide band AFR gauge, and start playing around with a fuel injection controller without knowing where you are or what you are doing concerning the AFR ratio, then this will end up with an overheated/detonated engine where you will see a piston that is scuffed at the "four corners".

If you look at the bottom side of a piston you see the piston pin boss. If you look across each pin boss it's solid aluminum with no flexibility. It expands directly into the cylinder wall. However, the skirt of a piston is relatively flexible. If it gets hot, it can deflect. The crown of the piston is actually slightly smaller in diameter on purpose so it doesn't contact the cylinder walls. So if the piston soaks up a lot of heat, because of detonation for instance, the piston expands and drives the piston structure into the cylinder wall causing it to scuff in four places directly across each boss. It's another dead give-a-way sign of detonation. Many times detonation damage is just limited to this.

What typically happens is that when detonation occurs the piston expands excessively, scurfs in the bore along those four spots and wipes material into the ring grooves. The rings seize so that they can't conform to the cylinder walls. Engine compression is lost and the engine either stops running, or you start getting blow-by past the rings where you see your swing arm and rear wheel/tyre covered all over with oil. That torches out an area. Then the engine quits.

So install a wide band AFR meter en make sure that you are using an AFR ratio between 11.8 and 12.6 at high load, it's no problem to have 14.7 at iddle

!!If you installed a kit with only a cylinder and a piston, then be aware of the fact that if you order this kit you take your own responsibility for the well functioning of the kit. Our company will take no action if something went wrong with your kit.

If you have no exprience at all with tuning and mapping fuel injection bikes, then we stronly recommend you to order the 160 Ultimate kit. If you installed the Ultimate Kit and you have abnormal wear, then you can contact us at