GS125 Running issues

tino · L Plate Warrior Joined: 06 Oct 2012 Karma :

Hi all,

I'm running out of ideas on what the problem could be so thought I would ask more knowledgeable people Laughing

Essentially it was running quite happily then one day really struggled to get home , would run happily in neutral just as soon as you put it into gear she died. Managed to get her home by revving her quite hard and changing gear later than I normally would.

Took the spark plug out to check that was ok and it was a nice 'tan' colour so seems to be running ok. Then checked the spark and found none or a very poor spark. So checked the ignition coil and found a issue with that so changed it for a new one and still nothing. Moved onto the CDI and found that was out of spec so got a refurb one online and used that. Now I get a nice blue spark , no shock behind it when I hold it mind ( not sure your meant to hold the plug to the ground point but that always let me know it worked .... )

She still doesn't want to run though , she is fine when cold ( usual cold start for her is a little bit of choke then back it off after about 3 mins ( or the time it takes to put my helmet on and lock up my house ) ) idles around 1500rpm - 2000rpm depending on if the lights are on or not. An feels good when riding her until 5 - 10mins and which point she dies and refuses to start. After trying for a while she will backfire then happily start again for a very short period of time.

Im not sure what the issue could be here , it seems to indicate ignition problems still however I am not sure what or where they are. All the wires have been tested for continuity and are fine , the ground point is good and all exposed bolts on both the engine and the frame show continuity to ground. So I don't think its that.

Sorry for the long post , just going through what I had done.

So does anyone have any suggestions / obvious things I have missed?

tino · L Plate Warrior Joined: 06 Oct 2012 Karma :

A bit more information....

The compression is nice and high , reading about 120-130 which is above the manufactures guidelines.

Also it seems that it stops sparking when its hot....which is why it dies. Although that could be me not finding a decent ground when the engine is hot. I can bump start her from there and she starts and runs for a bit again.

I don't think its the carb as its a relatively new one and nothing has been adjusted with regards to that.

hondakawasaki · Nova Slayer Joined: 03 Jan 2013 Karma :

have u tried a new spark plug Very Happy

tino · L Plate Warrior Joined: 06 Oct 2012 Karma :

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Check coil earth again. Thumbs Up

bypass2 · Spanner Monkey Joined: 12 Sep 2013 Karma :

maybe what you say a faulty earth. any earth wire getting hot.or bad connection

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

The actual coil bolts directly to the frame I think and the 2 mating surfaces are prone to corrosion.

tino · L Plate Warrior Joined: 06 Oct 2012 Karma :

Many Thanks for your replies,

Turns out it was a cable resting on the engine that as it got hot melted the sheath and grounded, when it cooled it broke the connection. I've just put heatshrink round it for now and made sure its still decent.

Also didn't help that the kill switch has started to play up now. Is this something that can be stripped down?

The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

Yeh it can be. Could have corrosion or something.