Bent Iridium Spark Plug Electrode

[Circlip]

I do believe that dragsters and the like in America do align the spark plug electrode before fitting the heads.
However if I had a Lycoming engined aircraft I would fit iridium plugs,-- but to fit them to an engine that was designed 50+ years ago,-- well I have my doubts at the necessity.

Looking at the Denso site today I see that the melting point of these plugs is 4400 degrees F and a slight decrease of the voltage necessary to jump the gap. Is this with a resistor lead and a resistor plug cap? it didnt say.

There was however an extensive disclaimer stating that increase in HP was not a certenty.

If you say the engine picks up quicker after a down hill jaunt then thats a benefit.

[Biscuit]

Acknowledgememts to www.Spark-plugs.co.uk


'Due to the properties of Iridium, the spark plugs centre electrode can be made with a much smaller diameter than with platinum, Gold or gold palladium and copper/nickel types without sacrificing service life. The spark plugs potential difference is more concentrated at the tiny Iridium tip and hence less 'spark jump' voltage is required - this can be as much as 5,000 volts less than with standard plug types. Ignition is improved and less strain is placed on the ignition system. Benefits of improved ignition/combustion include better fuel economy, increased power/acceleration and especially better throttle response.Service life of some OEM Iridium spark plugs can be as much as 120000 miles with very little degrading of performance in that lifespan'.

Regarding lining the plugs up, on the G11, fortutiously, the electrodes are well away from the inlet valve, from playing with the spare heads it would appear that the exhaust valve does not pose a problem

NGK Iridium IX types have a centre electrode tipped with Iridium alloy with a 0.6mm diameter. NGK believe this gives the optimum balance between performance and service life. Service life estimates can be up to 60000 miles for normally aspirated car engines and up to 20000 miles for motorcycles - this is extremely subjective though, a high revving motorcycle or extremely modified car engine will most likely wear plugs out in a few thousand miles'.

Regarding lining the plugs up, on the G11, fortutiously, the electrodes are well away from the inlet valve, from playing with the spare heads it would appear that the exhaust valve does not pose a problem.




Edited by - Biscuit on 07 Aug 2007 5:35:45 PM

[itma]

of course if you are, like me, still running on dismountable Lodge plugs with 3 electrodes then this is all academic.
single cylinder riders can be soooo smug

[GSAX1]

quote:
....still running on dismountable Lodge plugs with 3 electrodes..


I'm using the original KLG FE80 three-point detachable as fitted by the factory. I have a stash of these and they function perfectly no problem whatsoever. My twin starts first kick hot or cold and idles well. Of course service life of these plugs seems to be much less than modern types.

Michael

[geechr]

I agree with Biscuit that Iridium plugs make a difference - my G11 was running better until I made the fatal mistake and tightened them up up a bit more, which caused one of them to hit the inlet valve, as I have now been told during this thread.

To stop the problem I wonder whether using two of the special plug washers, to reduce the reach, would work?

[Biscuit]

I would suspect that it is the position in which the electrode ends up which causes the problem. Try what I suggested, ie marking the location of the electrode and seeing where it ends up, (this must be better than working blind), then add washers as necessaryEdited by - Biscuit on 07 Aug 2007 11:18:19 PM

[Circlip]

You could just use the low profile plug that the engine was designed for.
Sometimes at higher revs the piston is thrown up the cylinder reaching slightly further than at lower rpm, especially on its exhaust stroke,-- if the engine as a little loose!!

As Biscuit has experimented with a plug in a spare head and said that its not the inlet valve at fault, this is more likely.

[Biscuit]

Now here's a thing!. A friend has a G11, 1958 with pattern pistons. Due to a slight missfire the reason for which he has yet to trace, I lent him the iridiums from my G11, standard wire wound pistons.

He started the engine, one cylinder refused to fire, and found the plug gap had closed up.

Hope he hasn't ruined my plug.

[geechr]

[geechr]

As Biscuit suggested I have aligned the plugs in such an orientation that means that the earth electrode is away from the inlet valve. There is now no clash an the bike is back working very well.

It must be really close though....

Thanks for everyones help.

Chris Gee