Wednesday, 3 November 2021

Yamaha XT 125 engine rebuild parts

 These are the parts i use to rebuild my Yamaha XT 125 engines with


Firstly you need good gasket sets i always use thes NE brand ones never failed me yet





I use either SKF or Koyo bearings 




                                Buy these on Ebay UK here 



Athena Seals New oil seals need to be fitted on every rebuild                                                                           
Cagiva Mito Engine recommended rebuild parts





Ive had very good success with these piston from firefox but if you can find genuine on an auction then but them
 first.








For barrels i always try to rebore and oversize piston.

Sunday, 24 January 2021

Yamaha XT 125 How to test spark plug with multimeter to see if is it is good or bad

 Its a very easy but useful test to make sure your spark plug is ok , you may need to clean the electrode to ensure you get a good reading but all you then have to do is set meter to read ohms and measure from the spark plug cap end to the electrode tip , and then from end to body to make sure no leakage to earth.


Buy XT125 NGK spark plugs here on Ebay UK


How to test spark plug with multimeter to see if is it is good or bad

Get set up turn meter to ohms reading on dial and clean the electrode as below 

How to test spark plug with multimeter to see if is it is good or bad

Test between end of spark plug where HT lead cap fits and the tip of electrode the reading is very low only 1.2 ohms 

How to test spark plug with multimeter to see if is it is good or bad

on a dirty part of electrode the reading goes wild and eventually read 188.9 ohms so very bad and to avoid this clean electrode tip 



How to test spark plug with multimeter to see if is it is good or bad


Next test from spark plug cap end to the body to make sure no earth leakage your meter should read OL which is a good reading as it signals no leakage to earth via the body.

How to test spark plug with multimeter to see if is it is good or bad

See video of this process below 


Thursday, 5 November 2020

Yamaha XT125 R X regulator rectifier testing



Yamaha XT 125 for sale on Ebay UK


Yamaha XT 125 parts for sale on Ebay UK  



First ill show a quick test on diodes inside you regulator rectifier .

You are just checking current flow through the regulators diodes in forward and reverse bias.

Cagiva Mito 125 regulator and charging system testing .










I usually face the regulator this way and test as below 


Connect + side of meter to bottom left hand pin/ connector and negative or common to
upper left hand pin you should get a reading of 0.6 or just under here i get 0.512 so happy with that.



swap the leads around and you should get 0L on the meter meaning current is
flowing one way and not the other and diode inside regulator is fine.


Now do the same but on the far right hand side pins/ connectors 
test both ways again you should get 0.6 or close to it one way and 
OL the other again testing the diode.


Now test between the R/H lower pin and centre you should get a reading one way and not the other my reading is 1.172 and its a good rectifier regulator and show diode working 




Now test between the L/H lower pin and upper centre pin you should get a reading one way and not the other my reading is 1.181 close to above reading  and its a known good rectifier regulator and shows diode working 





Thursday, 22 October 2020

Yamaha XT125X XT125R Oil Pump Test < warning - oil pump failure engine seizure






I am having a lot of XT125s and YBR 125 engines in seized and i am not sure why , maybe bad oil maybe old thin oil .

Maybe running oil to low for pump to circulate , maybe i do not know !! .

or maybe its just coincidence .

here is a test to see if oil is circulating to the top of engine , do it regular and check oil levels 
regular as well , and change oils as per manual .

you need a 10mm spanner , that is it ! .




Yamaha XT125X XT125R flat battery , not charging , overcharging



Yamaha XT 125 for sale on Ebay UK


Yamaha XT 125 parts for sale on Ebay UK  



You need a good battery it a must buy good quality , especially with newer XT125r as they have no back
up kick start , which is a step backwards in my opinion .

find batteries to fit the Yamaha XT125r  here on Ebay UK or here on amazon UK









common problems Yamaha XT125r  flat - weak  battery

- Battery faulty or worn out , replace battery  after checking voltage levels , fluid levels and specific gravity .
- poor terminal contacts ( happens a lot )
-excessive load ( remove some of them lights , stereos whatever )
-faulty ignition switch
-alternator stator coil failure ( test for open or shorted coils )
-faulty wiring ie short on loom or loose connections (check wiring and contact clean all connector blocks )

battery overcharging

- faulty reg rectifier
-defective battery
-wrong battery size

Yamaha XT125r recommended or Genuine battery chargers are listing below




YEC-40 Battery Charger   
Amazon UK

 YEC-8 Battery Charger  

Yamaha XT125X XT125R engine will not turn over












I have had this often on Yamaha XT125r  you press the starter button and nothing happens , the engine does not turn over.



here are some possible causes

-blown fuse
-battery flat
-defective starter motor - or wiring to it
-relay faulty ( built into solenoid )
-starter button faulty ( sometimes need and heavy press to contact )
-starter wiring circuit
-defective ignition switch
-faulty neutral/stand switches  ( had faulty neutral switches on at least 4x xt 125s now )

Yamaha xt125r engine will not turn over

Yamaha xt125r engine will not turn over