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  • YUMINASHI 164 ULTIMATE KIT with Stand-Alone PGMA-FI Unit / IAT Enabled
  • Yuminashi 164cc Piston Rings treated with a hard chromium plating layer (Cr)
  • Yuminashi how to install piston rings guide...
  • Recommend Air Fuel Ratio's....
(Not possible to adjust without a wideband O2 sensor & gauge)
  • Recommend Air Fuel Ratio's....
(Not possible to adjust without a wideband O2 sensor & gauge)
  • Comparison between different types of big bore kits for MSX/GROM125, with the position from the 164cc Ultimate Kit.
2,950.00 Grams
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 Product Description


warning-sign-small.png **Don't use this kit without the Yuminashi high performance coil installed!! 
           If you don't have one yet, then you can order it over hereThis kit is not plug&play, you will need to buy a wideband O2 sensor and spend time to properly tune the standalone ECU to fit your setup, exhaust systems and climate condition or you will have to have access to a professional dynamometer tuning service. If you are not willing to do so, we strongly recommend this touring kit instead, which is plug&play ready and very easy to install and use164CC TOURING KIT (MSX125/MSX125 SF/GROM125)
The 2015 generation standalone ECU has been superseded by the new V8.9 2016 IAT enabled standalone ECU for narrow band and wideband O2 sensor. 

All new Yuminashi Ultimate 164cc kits shipped after Januari 2016 include the new 2016 standalone ECU to read and make changes based on the Intake Air Temperature ...

● Click here to download the 2015 V8.9 MSX 164 Ultimate Owners Manual.

● Click here to download the user guide for the new 2015 Standalone ECU / AFR datalogger 

● Please open this PDF file and use it as a guide to gain both, maximum performance and maximum protection against engine knock (very important).

● The 164cc Ultimate kit is great "all-in" starter kit with a great value for money which includes compared to the very first 160cc generation a slightly larger and lighter piston with a molybdenum coating on the skirt to have less friction. 



● With the Ultimate 164 kit you will have just like its predecessor a kit with improved performance/reliability without any risk of damaging the stock crankshaft, connecting rod or big end bearings. With the 2016 IAT enabled standalone ECU you have the choice to create and select 2 totally different maps. With the optional Off Run / Map Select Switch you are able to switch back and forth between the both maps on your standalone ECU while you are driving! We developed this kit under the assumption and common sense that you will install an aftermarket, better designed, freer flowing exhaust system. Using a completely stock exhaust system on a big bore kit will result in a hot running engine, more sensitivity to engine knock, difficulty in tuning and overall reduction of performance. 

If you don't have the Off Run / Map Select Switch installed, then you can select map 1 with installing the jumper that comes with the kit, and with the jumper removed you are selecting map 2.

If your engine temperature runs really high and your engine needs a break, then the ECU can be programmed in such a way to give your engine a break with reducing the pre-ignition and adjusting the fuel injection amount to keep you away from piston and serious engine damage.

(If you use the stock air filter you need to remove the restriction inside the stock air filter like you can see on this video from Motorcycle Projects on YouTube).

The 10-holes MSX/GROM big bore injector that comes with the kit guarantee a short and powerfull injection. This kit can be installed with the stock manifold and throttle body. (The optional USB Programmer Cable need to be ordered to allow you to tune the standalone ECU based on the additional parts you have installed on your bike together with this 164cc Ultimate Kit)...

This set comes complete with the SX290  8.2 high lift camshaft, and also with the special high lift valves to make a higher lift as stock possible.
The reinforced clutch springs that comes with the kit make sure that you don't miss one single RPM.

The piston from this 164cc Touring Kit is plug and play to be installed with the stock 125cc head.

This piston rings are produced on strict Japanese standards and since March 2015 are all rings treated with a hard chromium plating layer (Cr).
To read all details/information about the piston rings you can click on this link.

The new 2016 IAT enabled Yuminashi Stand-alone ECU / AFR datalogger is the new generation of programmable ECU units for Honda MSX125/GROM125 and is replacing the formal, first generation of Yuminashi stand-alone ECU units.

With the 2015 generation ECU we had build the programmable ECU based on your needs to make it as easy as possible to tune your PGM-FI engine and included both, a narrow band and a wide-band AFR meter in the package to make accurate AFR readings possible and with the 2016 IAT enabled ECU you are able to correct your values based on the outside temperature day in day out.

If you made your fuel map with a Intake Air Temperature from 30 degrees Celcius, and it gets 10 degrees Celcius colder, then you can enter a value in the IAT section to get your entire map back based on the 20 degrees IAT temperature when you programmed it.    

If you install this kit, then you need to install a 5 volt wideband O2 sensor to connect to the standalone ECU to get the tune right. We recommend the Innovate MTX-L gauge. The bung that comes with these optional O2 kits can be welded on the exhaust where you simply can connect the analog wire from your Wideband O2 gauge to the green wire from your new Yuminashi IAT enabled stand-alone ECU.

The next thing you need to do then (don't forget this) is to right click on the AFR gauge in the program, to select the wide band sensor option and you're good to go...

You need to order the optional USB Programmer Cable if you don't have one yet (the one from the formal stand-alone ECU generation can still be used), because you will need this cable to make the ECU work based on your local enviroment conditions! 

If you haven't a USB Programmer Cable yet, then please don't think that you won't need it, the stock base map won't be right to be used on your personal bike setup and local environment like humidity, elevation and local temperature, you can order it over here...

* Click on the CD's below to start downloading the software for the stand alone PGMA-FI ECU-AFR datalogger correcting program:

                   Driver install software (1.6M)
                  2015 ECM-AFR datalogger V8.9 Tuner Setup software (2.22M)

*Click on this link to download the .msi file needed to install the tuning program.
**Click on this link to download the .cfg file with the base map for the 164 Light Bore Kit (New map since 1 October 2015!)

-Screenprint IGN degree (Tps)
-Screenprint INJ VE (Map)
-Screenprint INJ VE (Tps)
-Screenprint Enrichment correction
-Screenprint (TRIM) SETUP


Click this link to download the 8.1 first generation stand alone tuning program... 

Click this link to download the manual from the 8.1 first generation stand alone tuning program in PDF file... 

● If you need the factory installed .cfg Touring Map from the 8.1 first generation standalone ECU, then click this link to download.

● If you need the factory installed .cfg Racing Map from the 8.1 first generation standalone ECU, then click this link to download.


(From our customer Joannick Deschamps, France (Europe))



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