Trained-Eye Jetting Consideration Request...

I'm the odd one running an air box behind my RS36 carbs, rather than the typical POD :evil: setup definitively recommended by the Mikuni Carburetor Company in the owners manual.

Ok, here's the deal with my bike. Dynatek 2000 ignition (setting #2 and 10K limit), solid core wires and res. caps, Accel U-Groove 142 plugs (Non-Res), Dyna 3 ohm Mini-Coils. Shindengen SH775 Series Regulator, and stock Kaw generator components.
84 GPZ camshafts in an 84 ZN/GPZ1100 bone-stock low-mile head, new std size stock Kawasaki pistons and rings, all freshly installed last Spring with approximately 7K miles on them now.
The RS36 carbs were fitted around a month ago, replacing the original BS34's, tinkered with for the past sixteen years. Now they are taking time-out in a bag on a shelf, where I'm becoming convinced they belong.

So here's my carb setup as of now. 132.5 Main Jets and #20 Pilot Jets. The Pilot (FUEL) Screws are turned out 1/4 to 3/8 from lightly seated. The clips are inserted one notch below center on the jet needles. There are no pops on deceleration, as it had with 17.5 Pilot Jets.
The spark plugs in the photo have a couple hundred miles with the above setup, and have developed a pretty consistent color across the batch. The insulators are grayish brown, and electrodes are clean.
The spark plugs (and tailpipe) have much better color with these carbs, not to mention the new power rush :ohmy:

I'm looking for feedback regarding the condition of the spark plugs, if they indicate my jetting appears correct despite the incorrect setup I am running behind the carbs. I have a set of new 22.5 Pilot Jets ready to pop in, but wonder if anyone thinks they might be better than 20's.

Thank you in advance for any input, as long as its not derogatory in-nature like mine.

Take a look at kzrider.com/forum/3-carburetor/342822-co...rk-plug-base-reading

It appears that the heat range is good based on the strap and that it may be running a bit on the rich side based on the base ring. Ed

650ed wrote: Take a look at kzrider.com/forum/3-carburetor/342822-co...rk-plug-base-reading

It appears that the heat range is good based on the strap and that it may be running a bit on the rich side based on the base ring. Ed

Thanks again, Ed

Could the richness be minimized with a finer pilot screw adjustment, or perhaps larger/smaller Pilot Air Jets than what the RS36's came with?
I want those annoying pops a thing of the past, or limited to Harley's where so-lovingly embraced. :lol:

Exhaust popping on deceleration may sometimes be eliminated or at least minimized by slightly enriching the carb pilot circuits.

This could be say 1/8 turn out (counter-clockwise) of each mixture screw (pilot screw on engine side of carb) or 1/8 turn in (clockwise) of each air screw (pilot screw on airbox side of carb).

Would try to not go any larger than the #20 pilot jets which are already one size over the stock 17.5 and seemingly already pretty rich when needing only 1/4 to 3/8 turns out from lightly seated.

The jet needle clip position looks to be one clip richer than stock, which won't affect mixture at WOT or at less than 1/4 throttle, but could be too rich during mid-range throttle positions.

Would suggest doing spark plug readings for each of the carb circuits after simultaneous throttle-chop/ignition-cut-off after steady riding in highest gear for one mile at 2000 rpm (reading for pilot mixture), again for about two miles at 70~80 mph (reading for needle clip position) and again for about a mile at WOT (reading for main jet).

The distances are estimates, which may require longer for adequate spark plug coloration, especially with ethanol gasoline.

Good Fortune!

Popping usually indicates lean or one carb way out of sync.
Steve

Guessing the idle mixture screws are too lean, causing the popping on decel, and the main jets are about 2 sizes too rich, causing the dark plug ceramics. Does it need much choke to get running from cold?

swest wrote: Popping usually indicates lean or one carb way out of sync.
Steve

No popping as currently set up. Had deceleration pops with 17.5 pilot jets, but none with 20's.

How do the plugs look now you have some miles on them?
Steve

daveo wrote:

swest wrote: Popping usually indicates lean or one carb way out of sync.
Steve

No popping as currently set up. Had deceleration pops with 17.5 pilot jets, but none with 20's.

Yes but the point that you only have the pilot screws open a quarter turn tells me that your pilot (idle mixture) screws are out of their range, and need to be opened up some and go back to the 17.5. Something isn't right to only have the idle mixture screws open only that much.

DGA wrote: Guessing the idle mixture screws are too lean, causing the popping on decel, and the main jets are about 2 sizes too rich, causing the dark plug ceramics. Does it need much choke to get running from cold?

Last sync a few days ago.
Choke definitely needed to start when cold. The rpms rise to around 2200 with the enrichener/choke knob pulled fully out. When pushed in, idle immediately drops to 7-800 for a short time before stabilizing around 1000 as the engine warms, and starts quick thereafter.
After a short cruise at 70+ the other day on the highway, the idle hung at around 2000 after coming to a stop, and dropped off after half-minute or so.
Could change main jets back to 130, or raise needle clips to the middle slot first.

DGA wrote:

daveo wrote:

swest wrote: Popping usually indicates lean or one carb way out of sync.
Steve

No popping as currently set up. Had deceleration pops with 17.5 pilot jets, but none with 20's.

Yes but the point that you only have the pilot screws open a quarter turn tells me that your pilot (idle mixture) screws are out of their range, and need to be opened up some and go back to the 17.5. Something isn't right to only have the idle mixture screws open only that much.

Please correct me if wrong. The RS36-D3-K pilot screw range is 1/4 to 1/2 turns out, according to page 2 of:

www.mikuni.com/pdf/rs_app_parts_lists.pdf

May be that i'm off here, but an idle mixture screw only open a 1/4 turn, maybe this is based off the early eighties lean mixture settings. At that much open, there would be practically no flow. And if you had idle instability as you said, hung idle, that also points to idle too lean. In any case, with warm summer weather, you should need no choke to start from cold. Might be a tad lean for the first min or two, but run fine. Cant hurt to try another half open I say.