I have a 160 jet and may try it in there. I did check the plugs and the electrode was brownish and the ring/base was a bit carbony with 2 1/4 or so turns out. If I remember correctly ?, this is a sign of it being a bit lean?
Sounds more rich. If it were lean the electrode and ground strap would be white/fuzzy.
The procedure I use is found at www.harley-performance.com in their carb tuning section. Plug reading is harder to do these days because of the increased technology and gasolines, but it is still useful.
If the bike was in such disrepair, I'd bet the PO had carb farts as a result of leaking intake seals and they jetted it up to fix instead of replacing the seals. 42/160 jetting on a basic stage one solid mount is a good place to start. Most of the time the 42 pilot is fine and at most you only need a 170 main. If it carb farts with 42/160 or 170 then I'd suggest getting a new set of intake seals.
The only reason that I checked the jets is because she said that she was having to stop for gas about every 100 miles. This took me back to when I did the work on another friends 2000 that was only getting ~90 per 3.2 gallon tank, which is the same that is on the 2003, before reserve. Way over jetted for a minimal stage one.
I did check the intake seals on the 2003 using the spray can method and there was no faltering of the engine.
The rejetting back to 42/180 seems to have eliminated the carb farts, but now I am trying to get the air/fuel mix just right. It seems to run rich at anywhere between 2 and 2 1/2 turns out. Next step, as stated in prior post suggestion by scuba10jdl, is to step down to a 160 (or 165), depending on what I have on hand.