OEM (kawi) needles:
73L = 2.735 diameter, 39.15 L1
72K = 2.725 diameter, 38.60 L1
The second needle is more rich in a couple of ways, as you (skip) say.
The L1 of the first needle is an interpolative guess, cuz there is no direct cross.
From reading your post, however, I'm sure you know that.
With the bike in generally sound mechanical condition, jetting isn't about the numbers...it's about what's right for your bike, your environment and your riding style.
The 'one step leaner' doesn't really apply overall when you're talking about needles. It depends on
where you want the 'step' in your throttle position.
From 1/8-1/4 throttle?...change the diameter
From 1/4-3/4 throttle?...change the L1
(This info from mxsouth keihin needle guide chart)
re: 'When motoring along on a short staightaway at around half throttle, the bike's exhaust note sounds raspy and not clean...'
Don't know what it sounds like, but you're describing a situation where the engine is going to be 4-stroking. With the addition of '.. it clears up' under load, I wonder if that is what you're referring to.
You will
never get a 2-stroke to run under light load without 4-stroking. If you do, you'd better turn it off quick, cuz something is wrong! That's the sound of a happy 2-stroke!
The 'raspy' note part is what you
do get with a sharply jetted bike. It sounds like the note is right at the end of the pipe as opposed to being buried under a bunch of metal.
blah blah blah...
The point is only you can correctly jet your bike for your situation. Set your main using a WOT plug chop test with a subsequent
correct evaluation of your spark plug.
http://www.dirtrider.net/forums3/showthread.php?s=&threadid=60392&perpage=20&display=&pagenumber=1
Other circuits are set by the seat of your pants/throttle response. You will not get any sense of 'correct' jetting on the needle using a plug read.
Generally, the air screw going 'long' (out say 2.5 or more) is a sign of a too rich pilot jet. Going 'short' (say less than 1 out) is a sign of a too lean pilot.
Unfortunately, there are a number of situations where that doesn't apply. ;)
Didn't I say blah blah blah already?
Must be a lack of reasonable questions to respond to of late........
So....sounds like you know what you're doing and why. So just do it! Never a good idea to jet 'by the numbers' or 'because someone said'.
Check out the RB carb thread in the archives. JD has a ton of good jetting info there. Also consider his (JD's) jetting guide. You can graph five needles at a time for fuel flow characteristics. Check it out
HERE
Rather than sticking with the B taper needle, consider a steeper slope (say a C, or 1'34" º) with a larger diameter. Something along the line of a CEL with the oem 5mm cutaway TV, maybe.
Good Luck!
God Bless you and your compatriots (based on your ID anyway).
Give saddam a kiss for me! ...if yanno what i mean.....