Plug chop

[jumjum01]

Did some plug chop tests today with BR9ES at WOT on my RD350 ypvs EFI... did not work out the way I expected. The "ring" does not change width at all, should be 1-2mm depending on who you ask for optimal AFR. It was less than 1mm on all 3 plug tests. On test "C" the bike smelled of petrol so I am sure it was running way rich. The color on top of the plugs changed, but the ring on the ceramic did not change width..
Plug A - "lean base"
Plug B - +10% fuel at WOT
Plug B - +20% fuel at WOT
Procedure used:
-Warm up bike
-Find long straight
-Change to new plug
-WOT through gears
-Kill engine at speed
-Change plug back
-Hacksaw plug

[Darrell]

Interesting. I see that the ground electrode of plug A shows the lean mixture, but plug B and C look about the same to my eye. The outside of the part you cut off, the threaded part of the electrode, looks much darker on plug C, but it looks dark on A, too. I'm surprised that the insulator looks pure white on all three plugs.

[silverstrom]

They all look very lean if you did the plug chop correctly.

I like mine to be very safe