Good idea to check plugs now and then.
I catched cracked carb boots (2-3) recently before causing real bad. 3 was cracked 180 degrees hidden under the clamp. Plugs white-grey. Ex valves same color, no melt down .
Dyno with A/F check important. Check from idle and slowly increase.
I had very rich idle followed by too lean up to almost 4000 rpm on 5th gear. After that rather OK.
Found on dyno, plugs were not that bad.
I have earlier checked with Yamiya no numbers 4-4 and with Lotus Root pipes on dyno that had 2 wideband lambda sonds. 2 runs, 1-2 + 3-4 without diffusers. Copper pipes stucked in as long as possible, the system sucks the ex fumes to the external mounted sonds.
This years dynos 4-2-1, 1 sond only.
My stock K2 with No number 4-4 felt OK all over so no AF check, only power craph.
Dyno guy had same feeling as me, OK.
Stock CB750 carbs with stock filter has not much to change.
Needle height and main jet size which I had tested on the road. Air screws also easy to test on road when testing various settings during a long ride with screwdriver in the jacket. Manual is correct 1 turn out (ev.+/- 1/8).
Plugs look OK too.
I had drilled the needle jet a little to reduce hesitations at take offs. The 2x2 smallest holes closer to bottom opened by 1.0 mm drill.
Longer ride will help to determine correct jetting.
Slowly increase throttle when riding from 2000 rpm to 3000.
Slowly decrease back to 3000. Slowly increase to 4000, decrease back to 3000.
Do this all the way up to 8000 if bike can.
If it stutter at slow increase but not at slow decrease - Too lean.
Stutter at decrease, not at increase - Too rich.
Stutter all the time- too rich which probably should be visible when standing still smoking black.
Needle heights and main jets easy to find this way by slowly increasing- decreasing- increasing... throttle.
Needles at around 120-150, main jets 140-190 kmh (CB750) so focus on the road too!!
Slow response earlier at WOT will improve with richer needle/ main if too lean before.
My K2 had too lean needles ,(middle) which I found when I increased main to 120 which improved middle range a lot, but stuttering rich at 160kmh.
Needles one notch richer, main jets 115 and OK. I had earlier tested 110 so I knew they were too lean at top.
(More restricted 341 pipes need middle needle and less main which verified on a friends bike this year)
Dyno important to verify. Other carbs with no known jetting really need dyno.
My TMR carbs where close, but I had to increase pilots a lot followed by lower needles so fuel screws could be reduced to solve the way too rich idle.
