Sparkplug failure

[Daniël Bos]

I keep reading how unlikely it is so I thought I'd share this.

 

A while ago my 346xpg would not run properly and after a while I found it was the plug. It had started leaking between the metal stub and the porcelain.

Replaced with a known good one (not a new one) and she ran fine for the rest of the day.

Halfway through the next day this plug failed as well, but with no external signs. Went off and replaced with a new plug and it's been fine but has now broken its plug again!

Is it just an extremely rare run of bad luck, or is there another explanation? The saw is quite new, October last year, used 4 hours a day, every day.

 

Any clues?

Thanks, daniel.

[spudulike]

I keep reading how unlikely it is so I thought I'd share this.

 

A while ago my 346xpg would not run properly and after a while I found it was the plug. It had started leaking between the metal stub and the porcelain.

Replaced with a known good one (not a new one) and she ran fine for the rest of the day.

Halfway through the next day this plug failed as well, but with no external signs. Went off and replaced with a new plug and it's been fine but has now broken its plug again!

Is it just an extremely rare run of bad luck, or is there another explanation? The saw is quite new, October last year, used 4 hours a day, every day.

 

Any clues?

Thanks, daniel.

 

IMO, the plugs are OK and you have tracking from the HT metal plug clip, down through the rubber cap to the earthed body of the plug, that is my best guess as to what is happening.

 

Had this once with a Kawasaki engined strimmer - changed the cap....perfect.

 

See if you can change the rubber cap - on some Husky spark plug leads, trying to pull the plug lead out of the body of the coil can damage the thing so would get some lube down between the wire and the rubber cap and then pull it off to replace it.

 

To have three plugs fail must be almost impossible.

[Daniël Bos]

The first failure was potentially a manufacturing fault, as there was evidence of leakage between the porcelain and metal, in an outward explosion type pattern.

 

The next two are definitively plug failures as a new plug sorts the issues and the plug does not work on another working saw.

 

What could break a plug? The saw ran on petrol mix for four or five tanks, aspen ever since.

[GardenKit]

What make of plug are you using, Rover?

[Daniël Bos]

Ngk plugs, all of them

[Graham]

Is the plug lead pulling on the plug somehow. That might cause the insulator to crack.

[GardenKit]

Ngk plugs, all of them

I was hoping you were using rubbish plugs and I could have said 'dont use rubbish plugs', but NGK are the best.

I've no idea whats causing your problem but will be interested to know if you find out.

[pleasant]

What NGK number are you using for the application?

[Daniël Bos]

Whichever one came out, 7a at the end I believe. Same plugs as in my ms180 and ms210 (the new 550xp uses a much smaller plug)

[pleasant]

..and that was the original, factory fitted plug was it?