KymcoForum.com

General => Technical | How To => Topic started by: Ruffus on September 16, 2026, 10:21:51 AM

Title: Sparkplug errosion
Post by: Ruffus on September 16, 2026, 10:21:51 AM
Strange things happened this summer as:
A colleague texted me his scooter, an italian brand, would run only intermittendly and is pretty hard to start.

Went there, tried, scooter started and run normal at first try.
Switched off, NO start.
-all the things checked like KILLSWITCH, SIDESTAND, FUEL, PLUGCAP, etc.
-sparkplug out (please see pics).

The middle elektrode was completely gone. It must have been fragmentarely there for a while to allow temporarely starts and run.

Ignition coil, cable and plugcap were in order.
I really don't know what caused that errosion.

Usually I saw such a failure on racing engines where mixture was too lean or the plug was way off recommended heatvalue.
Title: Re: Sparkplug errosion
Post by: Neil955i on September 16, 2026, 10:49:12 AM
Wow!  Never seen a plug electrode like that.  Even in my misspent youth!

Be interesting to know if the new spark plug wears unevenly?  Maybe the original was faulty in manufacture?
Title: Re: Sparkplug errosion
Post by: Stig / Major Tom on September 16, 2026, 12:11:50 PM
Massive gap! - that it ran at all with a plug like that is perhaps a testament to Italian .....something.
IMHO.
Cheesecake?

Stig
Title: Re: Sparkplug errosion
Post by: Ruffus on September 16, 2026, 12:49:40 PM
Might have been a factory fault on the plugs side too (was an original not a cheap knockoff). We will see how the new one behaves.

No cheesecake, "panini scaldate" and white Tokaj as a fee🛠😅.
Title: Re: Sparkplug errosion
Post by: Neil955i on September 17, 2026, 04:54:24 AM
Like your charging structure Ruffus, seems very reasonable. 🤣