General Category > General Discussion
Reading a spark plug
adaven:
On my '73 Eldorado I heard pinging on acceleration.
When I inspected the plugs, they were white with carbon fouling on one side.
I replaced the springs on the advance.
I set the timing at the third mark from the left at about 2200 rpm. The pinging is gone and it runs great.
Now the plugs are slightly darker, but still carbon fouled towards the grounded electrode.
How do I read this?
SIR REAL ED:
Without a picture, I would not put much stock in any advice you get from this post.
"White," Carbon fouling," and "slightly darker," are very subjective terms. It's like trying to describe the color blue without a picture.
This could rapidly turn into an "oil thread."
I've read a few articles (Kevin Cameron, Cook Neilson, etc, IIRC) over the years that the motorcycle manufacturers are very conservative in terms of putting spark plugs that are too cold in the bikes at the factory.
I've always had good results running plugs that are one, two, or even three "numbers" that are hotter than stock.
If the bike is running well, overthinking to find a "better solution" is often a self-inflicted punishment. The Justice of Physics!
adaven:
You're right I guess.
I'll take a spin out to the Slimey Crud today and see if I can get a picture to post.
SIR REAL ED:
--- Quote from: adaven on October 02, 2022, 09:10:36 AM ---You're right I guess.
I'll take a spin out to the Slimey Crud today and see if I can get a picture to post.
--- End quote ---
:grin:
opinions vary tremendously.
Some say modern fuel additives make plug reading questionable. Then there is the variation in techniques, throttle chop, WFO, 3/4 throttle, 1/2 throttle, etc.
IMO, too hot and too cold are obvious. It all depends on what you are after. If you are going for the perfect tune, then... "Your bike will never run as well as Fred's bike!"
Phases of the moon, time of the month, etc. are all effects that come into play. :wink:
Always easier to change plug heat ranges than carb jetting, etc.
RinkRat II:
Easy............... ....
Paul B :boozing:
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