I used a bottom up approach because my initial Carb ridability problem was a part throttle burble/hesitation that occurred at around 3000 rpm. I knew my jetting problem was associated with interaction of the pilot jet, pilot air screw, Throttle Valve Cutaway and perhaps the jet needle clip position. As you pointed in Post #5 "sounds as though you are lean at the transistion point between the pilots and the needles" Well, I wasn't sure which way but as you know I replaced the 1.5 Throttle Valves with those replated 2.0's and Sudco recommends using a much larger Pilot Jet to deliver more fuel in the pilot circuit since a larger Cutaway makes things leaner @ 1/5 to 1/4 throttle opening. I could have gone directly to Sudco's recommended #25 pilot jet but I decided to keep the mixture lean and bump the size of the pilot jet incrementally and make sure the pilot circuit plug chops were correct. Heck it wouldn't even idle until I installed # 20 Pilot Jet. That's one reason for the bottom up approach. Like the article you posted from Ian Williams states, "Carburetor troubleshotting is simple once the basic principles are known. The first step is to find where the engine is running poorly."
Second, I made no mechanical changes to my GS engine, although I will be. Same old Wiseco Kit, cams, pipe & carbs with the exception of the 2.0 T/V's. I did all of those engine modifications I listed over twenty years and performed plugs chops & readings @ sealevel. This would infer the 127.5 Mains should be rich @ 5100 feet.
I took the day off: Removed one K&N and marked the kill switch housing with tape to denote both 1/2 & 7/8 throttle position. Reinstalled the K&N and head off for another round of testing with hopes of checking both the Needles & Mains. I did a plug chop on the needles first, the #1 had a blotch of color on the insulator while # 4 electrode was pretty white but both plugs had brown residue/color on the inner shell. Looks like #23.
www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
Started Big Blue back up on the side of the road and was greeted by a Loud Knock emenating from deep within. Limped home with the throttle barely open expecting it to seize any second and highside me. Came back a few hours later pulled the plugs and performed a compression check with the throttle wide open. I recorded the following values 1) 135 psi 2) 130 psi 3) 125 psi (last one tested) 4) 135 psi. So I didn't hole a piston? It sounds like a rod knock . . . I am admittely over my head and I haven't rebuilt a bottom end and would humbly ask for HELP to diagnose.
I was so close to being done.
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