Sunday, 28 June 2015

Yamaha YZF R125 will not start no spark diagnostics



Yamaha YZF R125 Blog Index - Contents


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Going to do a post on not sparking , as just come across this again on a bike and id forgot everything
so had to go through all the tests again .

Id just like to say im not really that good with electrics but i know something test first , dont buy parts and read and learn as much as you can  .


First off check all easy stuff .

So -

Fuses , Check all of them , make sure they are seated corrected actually pull them out clean contacts and refit spray contact cleaner in the terminals

Battery , make sure its fully charged remove from bike and recharge dont just guess ,
and whilst doing this clean up the battery terminals and the negative and positive wiring terminals .

Test battery at the negative and positive terminals
If you have a voltage meter you can do some basic tests.
When the engine has been off for at least 1-2 hours with ignition key turned off,
100% Charged 12.60 to 12.8v
75% Charged 12.4v
50% Charged 12.1v
25% Charged 11.9v
0% Charged less than 11.8v

Connections and Connector blocks , go though all the connector blocks take them apart spray contact cleaner inside then then put them back together repeat this a few times on each connector as it will clean the contacting surfaces .  If there are any home made repairs or connections redo them , its sound like a lot of work but ive lost count of how many non running bikes ive bought and its been a faulty wiring connector .

Side Stand and Kill switch , fully confirm that these are working properly with a multimeter do not assume they are ok , do not buy any parts until you have tested these , ill do these tests on a post one day but they are simple , see the video below and the recommended book as well .

Generator test , tbh im sure the bike would run with a faulty generator but probably not for long
so i test this now , its an easy test and at the very least confirms it working or not , see our post on this here .

Pick up coil testing , this is what send a signal to the cdi to tell it when to generate spark signal , see out test fort his here .


HT coil , Next i would test the ht coil , first id test the primary side for 12v whilst turning the bike over , if you have got 12v here then test the coil if you have not got 12v to primary side of coil , then
its likely to be ECU ( if its not wiring fault ) , if you have 12v to here great you just elliminated all the expensive stuff , test the HT coils primary and secondary sides read this post here  .

CDI , if all else has failed try a known good CDI , but prior to fitting make sure all is funcition
properly on the bike it might of burned the old CDI out for a reason , ill do a CDI test post one day
if i can figure it out  .

Rectifier regulator , You should have found the problem buy now ive never got this far , now
the rectifier only changes the output of generator to DC to recharge battery and run lighting system so this will have nothing to do with the ignition system , but some have told me they changed this and
they got a spark and seeing as all else has failed !!  .

Oh someone pointed out i never mentioned the ignition switch , which is true , ive never come across this myself but it would be worth check continuity on the ignition switch .


Here is an Excellent video on NO spark fault finding watch it all !!







and here is and excellent book on motorcycle electrics buy it read it and learn !!








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