Rapid plug failure in Chummy

[PeterN]

I have a 1930 Chummy with a 1934 engine, high compression head and L86C Champion plugs.
I don’t do many miles but on the last couple of runs of less than 5 miles one or more have failed. Definitely plug failure as I’ve done the screwdriver to block test to check. Today I replaced 2 and 3. Previously it was number 4. 
Timing might be on the over advanced side but when the plugs are good it runs and pulls nicely.
Any thoughts on possible causes or alternative plugs would be welcomed

[Ruairidh Dunford]

Do you have photos of the plugs that you consider have failed.

[PeterN]

Hi Ruairidh , I’m out just now but I’ll post later, they are quite clean.

[Jeff Taylor]

Peter,

I was far from impressed with two new differently numbered Champion spark plugs I bought from a reputable supplier for my two-stroke hedge trimmer and petrol lawnmower. On opening the boxes both had serious manufacturing defects so I complained to the supplier and chose not to use them - there was no country of origin on the boxes, but I suspect China. I then bought a couple of NGK from another reputable supplier and the difference in manufacturing quality straight out of the box was very noticeable. Be aware there's lots of fake NGK and possibly fake other brands on the w.w.web, so buy from a reputable supplier. The NGK plugs I bought have 'Made in Japan' or 'NGK Nagoya Japan' printed on the box.

Champion L86C - these plugs superseded the previous Champion L10 many years ago. The NGK equivalent to L86C is NGK B5HS 4210 but as I mention above, buy from a reputable retailer.

Jeff.

[PeterN]

Here’s some pictures. Two different markings, different suppliers, but both very little use

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There are 2 different Champion logos so they came from different suppliers I think.                         

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Sorry, I double clicked, better too many than not enough?

[Tony Griffiths]

Peter,

I was far from impressed with two new differently numbered Champion spark plugs I bought from a reputable supplier for my two-stroke hedge trimmer and petrol lawnmower. On opening the boxes both had serious manufacturing defects so I complained to the supplier and chose not to use them - there was no country of origin on the boxes, but I suspect China. I then bought a couple of NGK from another reputable supplier and the difference in manufacturing quality straight out of the box was very noticeable. Be aware there's lots of fake NGK and possibly fake other brands on the w.w.web, so buy from a reputable supplier. The NGK plugs I bought have 'Made in Japan' or 'NGK Nagoya Japan' printed on the box.

Champion L86C - these plugs superseded the previous Champion L10 many years ago. The NGK equivalent to L86C is NGK B5HS 4210 but as I mention above, buy from a reputable retailer.

Jeff.

Here's the Champion box and plug that I received from the Green Spark Plug Company last Wednesday. They were out of stock of NGKs - I think they said that delivery was due early September - but suggested that this would be a close match. If Green Spark Plug Co. (who must order lots of plugs) has to wait months for delivery one must assume that they are the real deal. I hope this helps.
Also, see:
How to test with a multimeter: https://www.youtube.com/watch?v=vpH4O14EBxA
https://www.blingstrom.com/modmondays-fx...lfr6b-6481

https://www.ngkntk.com/newsroom/blog/emea/fake-or-not/

[Ruairidh Dunford]

The plugs in your picture appear to be fouled.

Too rich a mixture or oil coming up the bore? Modern plugs do not have a shiny glaze on the inner ceramic part any more, once fouled you cannot clean it and the plug won’t work.

[PeterN]

Thank you, I rather think it may be oil fouling but I’ll get some new and see how it goes.
Thanks again, an interesting video. BTW, not everyone knows that NGK is from BaNGKok.

[Ruairidh Dunford]

Try running with a hotter plug.

[PeterN]

I’ll try that Ruairidh . Cheaper 1st option than an engine rebuild!