GS 550 E the plug killer!!

[Ian W]

Hi all. I have a 1977 GS 550 E. She's very much modified with a hand made loom (not me) and a Boyer electronic ignition. There's also a set of non-standard coils of a brand I've never heard of (and erm, can't remember the name of right now).

The problem is the ol' girl is eating spark plugs on number 1 cylinder. If I change the plugs between 1 & 4, she'll run fine on four. But won't run on one? The only way to cure the problem currently, is to fit a new plug. It seems that when the plugs get to a certain age/ mileage/ use, they simply won't work any more on that cylinder even if they will work fine on another cylinder/ bike?

The plug won't spark on number 1 cylinder (or any of the others) but if I put it into number 4 (or any others) it works ?

I'm sure I recall some time ago a similar problem that was related to the coil. I have another coil off another GS I have and I know that one is fine. Is it worth just changing the coil? Is it a problem with the electronic ignition?



Any ideas ?

[BassCliff]

Hi,

Have you tried new plug caps? What kind of shape are the spark plug wires in? What do the plugs look like? Lean? Fouled? Is the rest of the bike properly maintained? Carbs? Charging system? Valve clearances?


Thank you for your indulgence,

BassCliff

[Ian W]

Hi,

The plugs are black, she seems to be running very rich. When I get the money together she'll be treated to a full service. I haven't tried replacing the plug caps, the HT leads look good visually, but I don't have the equipement to test them. She is overdue a service the poor ol' girl.