Yamaha R125 how to test Ignition coil

 

Yamaha R125 how to test the regulator rectifier

Yamaha R125 clutch juddering ~ Anti judder spring seats

The 2 spring seats fit inside the smaller first clutch friction plate, this prevents binding or nipping of the clutch when being operated.

See video of this below 

Another place that can develop judder or knocking on these clutches is the rivets on the drive gear , they become lose and can cause judder or knocking.

Yamaha YZF R125 ECU Pin out

Yamaha YZF R125 computer pin out.

This is my own numbering and not what is on the connector or in any books etc. 1 to 21

                  Number left to right in below table 

1) Black ~ Earth 

2) Red black ~ Power feed ?

3) Red ~ Crank sensor 

4) Green black ~ Cooling fan relay 

5) White black ~ Headlight relay 

6) Green white ~ Instrument panel ?

7) Yellow white ~ Instrument panel ?

8) Grey ~ Wheel speed sensor / Ins Pan 

9) Blue yellow ~ Ignition switch 

10) Yellow black ~  Fuel pump ( not 100% its black ) 

11) Yellow blue ~ Diagnostics / Ins Pan 

12 Green red ~ ECT 

13) Yellow green ~ Tip over 

14) Yellow ~ TPS / Air temp / Air pressure unit

15) Brown white ~ TPS / Air temp / Air pressure unit

16) Grey black ~ All sensors + Crank sensor 

17)  Grey red ~ Sensors except ECT

18) Pink white ~  TPS / Air temp / Air pressure unit 

19) Yellow red ~ Fast idle solenoid

20) Orange black ~ Fuel injector ( not sure if 12v or ground ) 

21) Orange ~ Coil Spark signal ( not sure if 12v or ground ) 

will add more got to do some tests and get voltages

TBC

Yamaha YZF R125 engine main , etc bearings sizes

These bike are getting old enough now that all bearings need to be replaced upon rebuilding so ill collect the sizes here you can buy kits bit usually knowing sizes and ordering Koyo buy size saves you money 

Some Bearing kits for sale here 

I use either SKF or Koyo bearings 

                                Buy these on Ebay UK here

Below i list the bearings i find in this engine ill add more as i get the chance but this one has worn numbers and some with non visible at all so double check before buying and help out of you know any sizes let me know.

L/H Crankcase 

Balance shaft bearing ~ 6202 

Crank main bearing ~ cannot see this

Input shaft bearing ~ cannot see this

Output shaft bearing ~ cannot see this

Output shaft sprocket seal  ~ Cannot see this

R/H Crankcase

Balance shaft bearing ~ 6203

Crank main bearing ~ 6305

Input shaft beraing ~ 6004

Output shaft bearing ~ cannot see this 

Yamaha YZF R125 cylinder head strip down ~ Cam shaft removal refitting decompression

Here are some photos of remomal of cam shaft from the cylinder head and video below with basic explanation of the de-compression cam.

Remove the bracket that holds the cam in place with bearing and 

it holds the rocker guides in place too and stops them spinning

As you can see below the rocker guide pins are losse and pulling free

 Below is photo of the pins and rocker removed ensure you do not mix up to aim ease of installation they are marked different too 

Camshaft now pulls free easily

De-compression cam closed

And open , when open it activate exhaust valve 

so there is no compression build up when first starting 

at a certain rev count the centrifual weight will fly out and 

operate de-compressor cam to the above position, compression will return and bike with start.

Here is the out and inner cam bearings 

See this entire process below 

Testing the valve for leakage in video below 

Yamaha YZF R125 starting starter motor system

 R125 starting circuit wiring diagram 

Video of the starter sprag clutch gear below