Lean Idle

StanG wrote: Just crossed my mind. Does the sensor being screwed to the welded bung act as ground?

If it’s a Bosch sensor, No.

Hi Zed_thirteen, you say that the plugs are fouling, is this a dry sooth or some wet stuff (fuel on the electrodes) maybe picture? How long can you drive before cylinder drops out, and what is the overall performance of the engine? Actually Scotch is the carb guru here, maybe he has some idea, and will add to it something constructive. In my opinion the modified filters often lead to unexpected behavior of the CV carburetors.

Hi Stan, some of the sensors have a virtual ground connected through the wires to the controller, but they are not there to act as the ground for the controller. Sensor body even if, or not attached to the car "Ground" are not meant to act as ground for you controller or display. For this they are extra wires coming out of you gauge directly. If you gauge is not coming on when energized using designated wires coming out of it than i suspect there is a fault somewhere. Did it work before at least once?

To deal with the LEAN condition, using the stock pilot jets - Remove 1mm from the tip of each of the 6 idle needles. Just keep in mind that the tips are VERY easily bent. Pinch the needles in your fingers and with the needle upright, VERY carefully sand the tip. Use a micrometer to gauge the 1mm and to get all 6 all the same. This will allow a greater volume of the fuel-air mix to the idle ports. The final tweaking on a running engine will be coarser (more sensitive).
For the record: Never done this - had no need to, but - It's something that's easy to do and worst case scenario - you only have to replace the 6 needles. If there's an improvement in the readings but you need more fuel/air - remove another 0.5mm.

Calibrated the sensor. Used some fresh fuel.

With choke on (warmed up) shows 13.5 or so. Choke off 22.4 (pegged lean) and engine slowly dies.

Revved up in neutral I see 13-17.

No ARF sensor... so no numbers unfortunately, but my current observation with a warmer weather. Today updated.

When a warmed up bike sits shut for 30 - 60 minutes, cools down, the temp. gauge shows zero, it doesn't like starting on full choke. I can start it with choke lever ALL the way down. It starts right away, at very low RPM's like in slow motion. Gibe it a minute and it picks up. Then - lift the lever a bit to run it at 1200 - 1500 rpm. Just an experiment. If liver just by a bit when starting, goes up to 2000 and I take it down to 1200 - 1500. In other words - starts without enriched mixture on a choke.

If left overnight - it likes starting on a full choke. I push the lever down right away, adjusting it to stay at 1200 - 1500 rpm. Going up and down depending on the noises. Seems a bit higher makes the engine quieter when cold. But a few short minutes and it's all gone with heat expansion and oil pressure.