Hello, I bought YB125 last year and convinced company to print me wiring diagram and technical specifications. I scanned it and I'm posting it for you.

Images are in resolution from scanner, they all have 9.5MB.

Preview:

Links to big images:

Wiring diagram (3.5MB)

Key to diagram

Technical specifications 1

Technical specifications 2

Technical specifications 3

Technical specifications 4

Technical specifications 5

Technical specifications 6

Technical specifications 7

I hope it will be helpful to someone. If anybody has information about hacking ECU or other usefull information about EFI on YBR125, please post it. I discovered one thing, fuel injector make clicking noise that can be misidentified as too large valve clearance

I'm wondering how strong alternator is? How much amperes can I safely drain from it?

Is there way to hack EFI and reprogram it?

Some information about diagnostic tool? Protocol, specification of diagnostic interface, etc...

Removing catalytic converter?

Baggage holder considerations?

Hello, I bought YB125 last year and convinced company to print me wiring diagram and technical specifications. I scanned it and I'm posting it for you.

Images are in resolution from scanner, they all have 9.5MB.

Preview:

Links to big images:

Wiring diagram (3.5MB)

Key to diagram

Technical specifications 1

Technical specifications 2

Technical specifications 3

Technical specifications 4

Technical specifications 5

Technical specifications 6

Technical specifications 7

I hope it will be helpful to someone. If anybody has information about hacking ECU or other usefull information about EFI on YBR125, please post it. I discovered one thing, fuel injector make clicking noise that can be misidentified as too large valve clearance

I'm wondering how strong alternator is? How much amperes can I safely drain from it?

Is there way to hack EFI and reprogram it?

Some information about diagnostic tool? Protocol, specification of diagnostic interface, etc...

Removing catalytic converter?

Baggage holder considerations?

This is most welcomed data to the YBR125 EFI community.

You may not be aware of how rare this data is. I've been searching all over the net for technical data on the fuel injected model for the past 8 months but all I could find is everything for the carburetted model. Many many thanks.

During my research you may wish to know that I have positively identified the same engine (in carburettor form) being used in the Yamaha TT-R125 which is a trail bike modified heavily in the USA. Mods include BigBor Kits (upto 170cc) Carb upgrades, Performance Cam changes to mention a few. 15HP is common place. Our EFI and catalytic based engines only produce just over 10HP whereas the carburetted models are capable of just over 12HP.

Even if we manage to achieve the original 12HP the improvement would feel significant.

Unfortunatly, I suspect that any mods done to our efi based engines will not yield the desired performance increases unless a method is found to re-map the ecu accordingly. I.E. removing the catalytic converter will probably not produce any additional power and may even reduce it ! I am suspecting that the engine will run much leaner without the CC.

Thanks for you contribution.

Hello, I bought YB125 last year and convinced company to print me wiring diagram and technical specifications. I scanned it and I'm posting it for you.

Images are in resolution from scanner, they all have 9.5MB.

Preview:

Links to big images:

Wiring diagram (3.5MB)

Key to diagram

Technical specifications 1

Technical specifications 2

Technical specifications 3

Technical specifications 4

Technical specifications 5

Technical specifications 6

Technical specifications 7

I hope it will be helpful to someone. If anybody has information about hacking ECU or other usefull information about EFI on YBR125, please post it. I discovered one thing, fuel injector make clicking noise that can be misidentified as too large valve clearance

I'm wondering how strong alternator is? How much amperes can I safely drain from it?

Is there way to hack EFI and reprogram it?

Some information about diagnostic tool? Protocol, specification of diagnostic interface, etc...

Removing catalytic converter?

Baggage holder considerations?

Hi again,

Today, I flipped open flip open my Fuel Injected YBR125's seat and tank to expose the totally undocumented ECU.

Its an 18 pin unit and appears (from the underside) to be resin filled!

I have also (thanks to your contribution) managed to identify the function of most of the 18 pins.

One interesting observation is that two of the 18pins (Black/White and Brown) are connected to the 12v supply which may indicate that one of them may be a mode signal used to switch the ecu into an alternate mode (possibly diagnostic or programming mode).

Results as follows :

Brown - 12Volts

Black/White - 12 Volts

Black - Ground

Red - Magneto Sensor

Blue - Throttle Body Sensor

Pink/White - Throttle Body Sensor

Black/Blue - Throttle Body Sensor

Brown/White - Throttle Body Sensor

Yellow/Blue - Throttle opening (Variable)

Green/Red - Engine Temperature Sensor

Yellow/Green - Lean Angle Sensor

Orange - Ignition Coil

Yellow/Red - Fast Idle Solenoid

Orange/Black - Fuel Injector

Yellow - Fuel Pump

Blue/Yellow - Rev Counter Pulse

LightGreen - Engine Diagnostic Indicator (Amber Light on Instrument Panel)

White/Black - HeadLight

If you like I can send you images of my finds.

Hello, I bought YB125 last year and convinced company to print me wiring diagram and technical specifications. I scanned it and I'm posting it for you.

Images are in resolution from scanner, they all have 9.5MB.

Preview:

Links to big images:

Wiring diagram (3.5MB)

Key to diagram

Technical specifications 1

Technical specifications 2

Technical specifications 3

Technical specifications 4

Technical specifications 5

Technical specifications 6

Technical specifications 7

I hope it will be helpful to someone. If anybody has information about hacking ECU or other usefull information about EFI on YBR125, please post it. I discovered one thing, fuel injector make clicking noise that can be misidentified as too large valve clearance

I'm wondering how strong alternator is? How much amperes can I safely drain from it?

Is there way to hack EFI and reprogram it?

Some information about diagnostic tool? Protocol, specification of diagnostic interface, etc...

Removing catalytic converter?

Baggage holder considerations?

I have a few answers to a few things.

ECU hacking you cant do it . max you can have a piggi back system to give more fuel and air to the bike but there is nothing available for the YBR 125

About the noise . Your tappets might have gone loose . hence the bike is become noisy.

Hack EFI ?? what do you want to do with it . i am guessing the YBR 125 has a open loop fuel injection system.

Regarding the diagnostic tool .its a useful tool where you can change the Air fuel mixture and basically have some control over your tuning . If you want to do some serious mods would suggest check if there any big bore kits for the YBR 125 and upgrade it to a 150cc or a 165 cc bore kit and just change the Air fuel mixture and fly .

PM me if you want to know more regarding the yamaha Diagnostic tool. I have a friend who sells it here.

I own a yamaha YZF R15 here in india.

Hi good afternoon, 

I'm so sorry for bringing this thread back from the dead, but I'm hoping someone has copies of the documentation originally share here.

All the links are dead 15 years later. 

I just bought an XTZ 125 and it needs a valve adjustment. 

Best,

IslandXTZ

14 years? I'd say its an old thread.
google carl salter, I'm closing this thread