Spark Plugs of Color

Not white, but sure ain't black... :whistle:

I've been out riding my BS34's a few times with all the pilot jet screws set at 2.0 turns out. Can I get an edumicated suggestion how to adjust each one to achieve the correct spark plug color reading?

Resister plugs. Are the caps resister too?
Steve

swest wrote: Resister plugs. Are the caps resister too?
Steve

Great ? I believe these combinations work to produce a strong spark.
Dyna 2000 with 3 ohm Mini-Coils currently feed through copper wire, and Non-resistor caps on Resistor plugs.
I also run Resistor-NGK caps on Non-resistor plugs (Accel U-Groove 142), which seem to work pretty well too.

Another thing...noting the FSM specs for the 84 ZN1100 LTD carburetor main-jets. It calls for 122.5 main jets on 1 & 4, and 127.5 on 2 & 3 with 37.5 Pilots.
Rather, it has 132.5 main and 40 pilots in all four, which may partially explain why 2 & 3 appear leaner, based on that FSM jetting recommendation, but bear in-mind I've got the 84 Unitrac bathtub head with the GPZ cams in there, so everything is out of wack with that to begin with, not to mention the V&H header/street baffle.

Middle two look a bit hot (lean) maybe.

bountyhunter wrote: Middle two look a bit hot (lean) maybe.

When closely observing the plug tips in the second pic, my logic suggests that 1 pilot adj screw needs to be turned-in slightly more than 4. perhaps 1/4 and 1/8 turns respectively. 2 and 3 might be better at 1/4 more turned-out.

Thoughts on that?

They look close. A slight peanut butter color. Are your screws in front of the slides or in back? If in front, in is lean, out is rich.
Steve

swest wrote: They look close. A slight peanut butter color. Are your screws in front of the slides or in back? If in front, in is lean, out is rich.
Steve

BS34 CV carbs have the pilot screws on the engine-side (in back of the slides). They are designed to control the flow of fuel rather than air, so tightening them (to the right) restricts the flow of fuel, where loosening (to the left) allows more to get through.

With that in-mind, is pilot-screw adjustment likely where the color correction may be realized, or could main jet size have something to do with it?

daveo wrote:

bountyhunter wrote: Middle two look a bit hot (lean) maybe.

When closely observing the plug tips in the second pic, my logic suggests that 1 pilot adj screw needs to be turned-in slightly more than 4. perhaps 1/4 and 1/8 turns respectively. 2 and 3 might be better at 1/4 more turned-out.

Thoughts on that?

Maybe, not sure if it's all pilot settings.

Are the carbs synced?

daveo wrote: With that in-mind, is pilot-screw adjustment likely where the color correction may be realized, or could main jet size have something to do with it?

On mine there is a transition region where the pilots and mains both have a lot of effect. Depends on RPM and throttle opening.

Are your needles adjustable?
Steve

Moving subject from Electrical to Carburetor today

See: Mikuni VM 33 Carbs

The carburetors were carefully synchronized a few days ago with a Morgan Carbtune Pro, and I'm loving the synch out of it.
I wish the needles were adjustable, but are just raise-able with washers.

I really wonder what that FSM spec mentioned earlier for main jets is all about. It seems odd for the center carbs to have different main jets than the outer two, but that is what Kawasaki called for with that head from the 1984 ZN1100 LTD, and the carbs were slightly different design than the original 1982 BS34 set which is on it.

Not sure if a set of VM33's could net an improvement over the way this engine runs as it is.

daveo wrote:

swest wrote: They look close. A slight peanut butter color. Are your screws in front of the slides or in back? If in front, in is lean, out is rich.
Steve

BS34 CV carbs have the pilot screws on the engine-side (in back of the slides). They are designed to control the flow of fuel rather than air, so tightening them (to the right) restricts the flow of fuel, where loosening (to the left) allows more to get through.

With that in-mind, is pilot-screw adjustment likely where the color correction may be realized, or could main jet size have something to do with it?

My understanding is that this is where throttle chopping comes in. A Dyno makes this easier of course, but for the most of us its roadside mechanics. You want to mark your throttle with 1/4, 1/2 and 3/4. Take the bike out get it up to temp. Start with fresh plugs or cleaned ones. The idea is to note your throttle position and turn the bike off while holding the throttle in that position, coast to the side of the road and pull a plug. Depending on the color and the throttle position it will tell you where and what you need to adjust.