Intermittent loss of spark (Agility City 125) - SOLVED!

[jeeves]

A bit of a lengthy post...

For the past few months the scoot has randomly lost spark.
It first started as a hickup, then it would last a bit longer.
A few times after that it would stop at higher speeds. I would then stop by the side of the riad, turn ignition off and on and it would continue as if nothing happened.
It started doing that in the first 5 minutes or so on first start in the morning. After that it would be ok.
At this point I changed the spark plug.

A few weeks ago I was going back from work and stopped to buy a few things at the grocery store along the way.
Sat on the scoot, started up ok, and then it just stopped.
Couldn't fire it up again.
The engine was turning, but from the sound of it there was no way it was gonna start.
Had to leave it there and get a ride home.

The next day I came with a friend who has got a pick up to put it and bring it home.
Tried to start it, and it fired right up!
Rode it back home. There was a slight hickup in the first few minutes into the ride, but was ok after that.

Orders a new pick-up magnet, and new ignition coil.
The other day it couldn't start, so I first swaped the pick up - couldn't start.
Then I put in the new ignition coil - couldn't start.
Then I changed the plug again - nothing....
After that I put back on the old pick-up and coilnd started checking the wires as much as I could. Didn't see any exposed wire or bad connections.

Running out of ideas I disconnected the + terminal from the battery and left it like that for about 1 hour.
Connected the terminal back and the damn thing started!
It's been working for the last few days.

Was this a random event?!
The only thing that comes to mind is a fault CDI, but don't have anyone near me to try and swap it with another one.
There are a few on eBay that I can get for about 50$, but it's not original Kymco, and I've had bad experience with aftermarket parts.

Any thoughts people?

[jeeves]

When CDIs go, they go completely.

Have you looked at the spark plug cap itself?  I note that you've changed the plug already.

The new ignition coil I bought came with cable and plug cap, so it's probably not that.
A few years ago the original plug cap broke so I got a much better NGK plug cap that is on now.

[Viper254]

That's infuriating. Without going deep into electrical faultfinding it's hard to know where to go next.

It's worth getting the block connectors off and cleaning them up to ensure all connections are good.

[jeeves]

That's infuriating. Without going deep into electrical faultfinding it's hard to know where to go next.

It's worth getting the block connectors off and cleaning them up to ensure all connections are good.

Will try.

It died again today after working OK this morning. Can't start it.

[jeeves]

...aaaaand went to the garage a few minutes ago and it fired right up   

really driving me crazy now... 

[CROSSBOLT]

Intermittents will drive you insane! Consider this: you know what it is NOT. That is more than you knew before. I agree with Viper that electronic things are rarely intermittent, they work or don't. You have a bad contact problem either in a ground or wire broken or insulation rubbed away grounding something that should not be grounded. I would suspect any connector and the wiring harness by the steering head first. Use dielectric grease on each connector when you push it back together.

[jeeves]

Intermittents will drive you insane! Consider this: you know what it is NOT. That is more than you knew before. I agree with Viper that electronic things are rarely intermittent, they work or don't. You have a bad contact problem either in a ground or wire broken or insulation rubbed away grounding something that should not be grounded. I would suspect any connector and the wiring harness by the steering head first. Use dielectric grease on each connector when you push it back together.

Intermittents will drive you insane! Consider this: you know what it is NOT. That is more than you knew before. I agree with Viper that electronic things are rarely intermittent, they work or don't. You have a bad contact problem either in a ground or wire broken or insulation rubbed away grounding something that should not be grounded. I would suspect any connector and the wiring harness by the steering head first. Use dielectric grease on each connector when you push it back together.

Checked the ground wire to the frame - it's ok, no rust, nothing loose.

If I did have a wire grounding somewhere wouldn't the fuse blow?
I have only 2 fuses -  main one, 30A, which I finally changed today from a glass fuse (really Kymco???) to a blade type, and another one (don't know what it's for, have to check manual) and both are ok.

It's gotta be something related to the ignition, everything else is working.
Engine turning, lights working, can smell gas when it can't start so fuel system seems good, fuel gauge working...

When it starts it works like there is nothing wrong, except a short stumble that sometimes occurs in the first  few minutes of the first ride of the day.

[CROSSBOLT]

There is more than one grounding point and they must be taken apart to inspect the actual contact. You CANNOT check by outside appearances.

[Viper254]

It's a very different bike, but I was working on my Honda SH50 last night and couldn't get a spark - it turned out to be a loose connection at the CDI. Worth cleaning up that one too

[jeeves]

It's a very different bike, but I was working on my Honda SH50 last night and couldn't get a spark - it turned out to be a loose connection at the CDI. Worth cleaning up that one too

It was one of the first connections I unplugged, checked and sprayed with contact spray.

Thanks for the input Viper and Crossbolt 👍

[CROSSBOLT]

 

[Viper254]

Just wish we were getting somewhere

How does your side stand switch look? That can kill the spark too!

[jeeves]

Just wish we were getting somewhere

How does your side stand switch look? That can kill the spark too!

Agility City doesn't have a side stand switch.

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[jeeves]

Today the damn thing started again, so while it was running in the absence of better ideas I started wiggling wires and taking off contacts that are a part of the ignition loop.
The scoot has a TPS and when I pulled it of it turned off.

I spayed the contacts (3 wires, 2 going to the CDI) connected it, but the scoot couldn't start. Started wiggling the wires around it and the connector to the CDI and it started.

The wierd part is that this time the engine kept running even when I disconnected the TPS?!


Googled why do I even have a TPS on a engine with a carburator.

This is what I found:

"The TPS provides input to retard the ignition when the throttle is opened, to prevent pinging. 
It allows the engine to run with advanced timing when the throttle is closed, improving efficiency."

This still doesn't explain the total absence of a spark when it can't start...or does it?


At this point I suspect the TPS or CDI.

All the connector I checked are ok, wires look ok, I shaked and pulled all over, but I didn't split the wiring harness, so who knows... even been thinking of buying a second hand wiring harness and swapping it.


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[jeeves]

The scooter is working again!

Short version - it was the CDI

Long version -
Soooo, sometime mid December last year I ordered a new replacement Naraku CDI from Racing Planet
https://www.racing-planet.de/cdi-unit-naraku-racing-for-kymco-lfc4-p-264409-1.html?backcPathco=14&cPath=26_8819

It came in a few days.
First I tried to start the scoot with the original CDI - no go, couldn't start.
I then put in the Naraku CDI, but it could start either! WTF?!
I could only hear a high pitched sound coming from the CDI for a brief moment after I would stop pressing the starter button.

I sent an e-mail to Racing Planet, describing the problem.
They answered in like 30 minutes!
After a few mails back and forth they asked me to take a picture of the scooters registration permit to see the VIN number.
After a while they answered that they are not sure why it's not working, that I can keep the CDI and I will get a full refund!

Ok, so got my money back, but the scooter was still not working.
Looked at the ads in my country (Croatia -small country), and found two original second hand CDI's.
One was 30US $, but the seller didn't want to give a guarantee that it works.
The other seller asked for 54US$, no guarantee, and 65US$ with guarantee ! + postage

Both were from 2009.

Looked a bit on the net and found 2 on UK eBay.
Ended up buying a 2012 model for 15 UK £, but the postage was 23UK£ (ouch!)

Finally, a few days ago I put it in and all is good!
Have done only a few short rides, but it looks like it's ok!

First 3 pictures are the original and Naraku CDI, last one old and new original CDI

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