Topic: Plug gurus, rate my plugs!

[OneWheelDrive]

1974 K0 CB550 bored to 605, 650 cam, Uni pods, delkevic 4-into-1 with small baffle, hondaman trimmed advance spring, timing 2 degrees advanced, 38 pilot jets, 110 main jets, needle clip 3 from the top. Bike runs great from idle to redline, but there's some stumbling and popping when cruising in the mid-range. I'm thinking up to 40 on the pilots is in order.

[CB650CPastor]

Those plugs look good to me. I would try moving the needles one groove richer.

[mrfish2]

Is that a plug chop or did you just pull those out after riding around in multiple throttle ranges?

If it's the latter then you'll need to go back and do the proper plug chops to get an idea of what is happening in each throttle range. Overall they look decent if not a tad lean.

[OneWheelDrive]

Is that a plug chop or did you just pull those out after riding around in multiple throttle ranges?

If it's the latter then you'll need to go back and do the proper plug chops to get an idea of what is happening in each throttle range. Overall they look decent if not a tad lean.

That's a plug chop while experiencing the popping.

[flybox1]

at what throttle position?
RPM, speed...they are irrelevant in a plug chop. 
...and what are your mixture screws set at?

[OneWheelDrive]

at what throttle position?
RPM, speed...they are irrelevant in a plug chop. 
...and what are your mixture screws set at?

Between 3-4k rpm, maintaining approximately 1/4 throttle, mixture screws are 3/4 turn out.

[flybox1]

once you get to 1/2 throttle position, does the symptom go away?

how are you measuring 1/4 throttle position? 
do you have indicator marks on your control & throttle, or is it a guess?

[flybox1]

if truly at 1/4 throttle pos, your slide needles are barely supplying fuel to make a difference.
you're right in the mixture screw/pilot jet wheelhouse, so, go 1/2 turn RICHER on all mixture screws, ride test at 1/4 throttle pos, and if that doesnt get you the result you want, go to 40pilots and back to 3/4 turn on the mixture screws, and retest.
be sure to use OEM Keihin jets