No spark on one side
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I really really Need some help I have a 2010 hyosung Gt125R Which I’m in the process of restoring the problem I have and I cannot seem to solve is the bike only sparks on one plug And the other plug shows no spark at all. I have have brought new plugs and the coil packs But the one plug still has no spark. The bike will try and run on one cylinder but as you know it’s terrible , So what I am asking is how can I have one spark on one plug and no spark on the other plug ( I have swapped the leads and plugged around With the same results) Is it possible that the CDI unit can do this by only sending a spark to one plug?? Or can it be the stator? Or maybe something else I haven’t thought of
Any help would be very much appreciated .
Thanks
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Hey,
Welcome!
Let’s get to it…
- Which part of the harness is not sparking ? = Front or Rear ? (in otherwords , which engine is not waking up?
- Has the harness shown any signs of rust? => Try contact cleaner ?
Got a meter? = See it stays on 0 ohms (dead wire or a break somewhere) or the numbers go to infinity when on 10000 ohms (mark on meter)
See the rear coil ? = if it has a blue/white strip wire colour ===> Probe there. and go to the cdi plugs => find the same colour to see if the circuit is complete.
Also, go to the stator unit ==> See the “2Pin plug” coming from the stator => Put your meter to 200 ohms and tell us the ohms it says on it.
I feel like we want to be sure the “harness” is actually not broken in some hidden places resulting in loss of spark signals going to the coils to fire them up.
The CDI rarely fails but if it did , then it was likely a chinese clone or the stator & regulator (married together sadly) toasted it up. = followed by a bad battery cells that was annoying the overal electric system that made it go haywire.
I hope you get somewhere , keep us posted.
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Please also look at this topic for the CDI diagram to very the wires are going in the right places.
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Hi
I’ve tested the white and blue wire and the front coil black and yellow wire and these ok no wires broken . I have tested the two pin wire coming out of the stator and it shows 2 homs, I’ve also tested the stator the voltage regulator or (R&R) and the battery and both coil packs and all seem good And I do have a power jump box just in case I need a bit more kick ,
All I have to do now is test the harness, If that is ok then i’m stumped 🤔
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Hi Marcos, how are you?, I saw your answer to my question in the other topic and came here, well my bike is not having sparks in both cylinders, I’ve changed the spark plugs and coil and I’ve also checked the CDI connection and it’s everything is OK!
Maybe this ….
- Faulty Stator or wrong stator fitted.
- CDI unit faulty
- Wiring harness has a break (wires broken inside somewhere along the harness)
- Side Stand Switch (Bypass it) or check wires are not rusted if it is bypassed
- Clutch Switch Handlebar (don’t bypass it) but replace it. Take old switch out and find another bike at local bike shop , and find a matching switch, it is common part for many bikes, just find the size that fits Hyosung
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Hi I’ve tested the white and blue wire and the front coil black and yellow wire and these ok no wires broken . I have tested the two pin wire coming out of the stator and it shows 2 homs, I’ve also tested the stator the voltage regulator or (R&R) and the battery and both coil packs and all seem good And I do have a power jump box just in case I need a bit more kick , All I have to do now is test the harness, If that is ok then i’m stumped 🤔
What “Ohms” was the stator 2-pin plug ?
Don’t jump start on a live running car or truck = that’s how it fries everything.
You can take the battery out of the car and test with your bike inthis case or make sure the car/truck is fully off and runs 12V! (some vehicles are 24v!)
Good luck!
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Hi sorry for delay
I’ve been working on the bike all Sunday testing things like stator/ Power regulator/ cdi/coil packs and the loom all seem to be working ok but the loom has had some work done to it, some wires have been cut and re connected ??? So this weekend I’m taking the loom out and rewiring anything that look bad ,
The ohms reading on the 2 wires ( green and blue ) come from the stator is 00.1 . I have also noticed that tachometer Doesn’t work Properly it will jump up 1 or 2 on the clock when i turn the key ,
I’ve been reading that the tachometer are wired up to cylinder 1 on most bike and if they is a fault with the tachometer cylinder 1 can stop firing , I’ve also tried a good car battery With the same results no spark on cylinder one.
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I believe the stator is gone , can you confirm again = Switch your meter to under 200 ohms (hundreds, not thousands/K’s) , then tell us the figure again ?
Yes the tacho reads cylinder one , cylinder one gets the signal from the CDI , the CDI, translates both coils to the correct spark responses based on the feedback given by the stator unit.
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Hi I’ve tested the 2 wire plug (green & blue ) 81.4 ohms on 200 and I’ve test the 3 yellow wires coming out of the stator 01.7 ,01.5 , 01.4 ohms on 200 . I hope I’ve got it right this time lol . Thanks for all your help Marcel
Yup time to change the stator, it’s out of spec especially the yellow wires. And it is a “MUST” to get a new regulator with a new stator too. It’s too important.
Drain the oil and look at the stator unit , take a picture and show us please (I have known ex-owners to try switch things up) not all 125 stators are the same (Thats why our shop has 2 separate 15 stator listings)
Also it is “possible” you may need a new CDI ? Take a picture of it and show us ? (Just to make sure past owner didn’t try to use a GV CDi than a GT one)
This is assuming all the coil wires at the coils are not broken and the same colours are the same on the cdi plgus = then i can’t see anything else breaking sparks apart from the stator unit
I can’t see the “Clutch Lever” switch being faulty as it would stop the rear coil sparking too. Don’t bypass it.
If you are suspicious of it , buy a new one from our store.Side Stand Switch = Bypass it and as Simon on this site would say “put a paper clip across the plug” to bridge it and tape it hard as rust in the wires will cut sparks off 100000%
Regards
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Hi
After much fun i’ve uploaded the pictures of the stator and my 2 cdi,s both came with the bike.
I’ve just ordered a new cdi but the stator and Power regulator will have to wait until next month because If I order any more bike parts I will end up single lol .
The clutch switch is there it was just hidden And the stand switch Has been bypassed I’m now going to take out the loom and repair all the bodged up Repairs
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I’ve just fitted a brand new CDI and nothing still the same
no sparks on either coil #?~ or just 1 coil with the new cdi ? which coil sparks on the new CDI ?
Also can you show us where you got the new CDI from ?
I can see the flywheel is a modified MS3 scooter rotor and modified MS3 stator you have (18-pole type for 125cc) = Those new ones don’t exist anymore but we still custom ones instead. It’s getting harder to get 2002 flywheels , so make the order happen when you can as one day i will mark that catalogue as “Sold out” (can’t get anymore all over earth lol) , the sellers i work with have shot up their prices for me to buy their 2002 rotors that work with my stator kits. Frustrating sometimes when i need to keep costs down for everyone in UK
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Hi
It’s still only firing on the rear cylinder , I how have 3 cdi now and all are still giving the results, I brought my new cdi from grandad.com .
I’ve tested the pick up on the flywheel and that’s seems ok, I’ve also taken the stator out of the bike and gave it a good clean and then done a bench test on it and your right it is a little over what it should be.
If you could see the wiring it looks like someone had taken a chainsaw to it and reconnected it all with push fits And electrical type lol , So I think I will need to sort this wiring out first to make sure All the connections and wiring are good, I don’t want start spending money on stuff that I might not need .
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Hi Sid, 2 weeks ago you said you’re bike is still running on only one cylinder. I am having the same problem with GT250R (2008).
Your posts have been very helpful & i hope you get your bike running. Please post the good news.
I was just getting the feel of my bike before half of it stopped working. Man, I hope it’s just the coils. Good luck. 😎
-----LaserBeam---->
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Fair enough, take all the tape off , investigate the loom 1 strand at a time using your meter to test for any breaks.
Then re-wrap it all again nicely with fresh harness-tape (electrical tape that is proper so you can keep some water or winter misty air out with can cause wires to go brown inside)
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I forgot to mention it’s the front cylinder that is not sparking
Hi all. think i have same issue. My GT250R had a cooler front cylinder when i bought it. It ran rough at 6-7000rpm but i mostly fixed that, with some fuel cleaner, bigger fuel-filter, Goss fuel lines & NGK CR8EK plugs. It idled at 2050rpm, when warmed up, so i turned the idle screw a touch got it t0 1450 rpm. The bike was running really well, could get to 10,000rpm & i was happy. But i knew FRONT Cylinder was producing less HEAT (feels heaps colder) than REAR Cylinder.
Found some fuel spray in the air-box. Looks like fuel comes from the FRONT carby, for Front Cylinder. Bike still ran well. Then i removed the Ignition Coil for Rear Cylinder. Replacement coil did not fit so i replaced the old coil. It started, warmed up a bit, took me about 10Km away then it stopped at the traffic lights, at night. Had all my gear on; i was hot when i finished pushing it home. Next day bike started & idled, then stopped firing on Front Cylinder. I’m getting new coils & i guess a new CDI unit.
Do you think the fuel in the airbox & COLD Front Cylinder mean the TIMING is out, on Front Cylinder?
Or is that just from inconsistent spark or a lack of spark? Hoping the carbies are ok. It ran well for weeks.
Any advice greatly appreciate, many thanks. 💡
-----LaserBeam---->
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Try a fresh set of CR8E plugs , i don’t think Hyosung’s like the “K” code at the end of the plug, so it could just mean wrong plugs.
Try that and update us with a new topic with a bit more history of the bike (yes you can repeat the fixes you did in the past, so it might save us repeating old suggestions tha you tried already)
Do a compression test on full throttle , both plugs out , and tell us the PSI readings on a new topic. (Do this after the bike has warmed up)
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