No Spark. No 12v to coils :(

[IJustWantSpark]

Bike Model = : GT125R

Hi guys,

feeling pretty desperate now feel like I’ve check everything and would love to be able to ride my first bike this summer.

Anyways, the situation is no spark. 2.3v to one coil and 0v to the other with ignition on. I’ve replaced: stator and pickup, coils, spark plugs, cdi unit, rectifier regulator, battery

2.3 v and 0v to the cdi unit aswell.

Ive recently found a pretty crusty diode pack – not sure what responsible for doesn’t effect volts to coil when unplugged

Any help / advice would be much appreciated !?!?
Or if anyone knows where I can find a replacement wiring loom for it? Previous owners been tinkering with wiring loom I fear!

[♠️ M77]

is it possible to upload a picture to this forum , we need to see the harness near the battery and also the dashboard, this will tell us if its an RC model or older R model, if the last owners have been making a botch job toit or not.

Hyosung doesn’t make new looms for GT anymore, so we have to preserve what you have.

Blue-wire ends up at the CDI (Rear Coil) and Yellow-Black wire is at the CDI for front coil (which is shared with stator and dashboard for rpm signals)

Here is a CDI pin out too (See reply from @Cobra2)

Needing a little help with my current project (+GT125 CDI PIN OUT)

[IJustWantSpark]

Hi thanks for getting back to me, I’m sure it’s a RC model as it states this near the part number on the wiring loom. These are all the pics I have at the moment, I can take more if needed:

[♠️ M77]

Using a multi meter, check the same wire colours from this thread below

Needing a little help with my current project (+GT125 CDI PIN OUT)

And verify the coil wires are not broken towards the CDI or fray, otherwise the meter would say “eg. Blue/White Tracer wire for rear” no signal since its broken somewhere along the harness or it will tell you the circuit is complete (no breaks in the line) , then we should check the clutch Switch (Dont bypass it as fake neutrals can happen , rare but does happen) but you want the CDI plug to know it can sense it at the front handlebar lever switch , then also check sidestand (bypass it hard) , if it is bypassed sidestand, remove it and check the sidestand bypass wires did not get rottten (it makes it very hard to start the bike!)

These 2 I just mentioned do cut sparks off if the CDI can’t sense it.

Worst case scenario is that you may need to remove the harness and fully examine it , then check the coils using the link below:

Rectifier – How to Test Stator , Battery , Regulator – GT125R Carby

Check their resistance and report back the figures. Check your HT caps too. Then test again for sparks , see if they are bright blue or just very dull yellow sparks. (Becareful though as you don’t want to spark anywhere near fuel! – So just be wise)

Hopefully we are not looking to replace the CDI as the last resort or the bike has the wrong stator fitted. (Stator = No sparks will happen unless the CDi reads the stator’s pickup coil first)

RC & OIder R models use different flywheels, previous owners may have tried to put the wrong stator and bike wont start , it is just an idea, you will see for yourself if it is correct. RC stators rarely need replacing unless they got cooked by a crappy OEM Reg Rec

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