When the diaphragm is torn, the slide wont rise. So, she will go lean in higher rpms. Wont effect idle or lower rpm running at all.
for pure gas Im in the same boat. Down here in Champaign Illinois. (3 hours south of you)
Its about a 1.5 hour round trip for me to get pure gas. So I buy 10-15 gallons at a time.
Which reminds me its time for me to make the run.
Some guys claim to have good luck w aftermarket, I tried the JBM diaphragms once. They went directly into the trash can. $40 for the pair wasted. My 360 wasnt ridable with them. http://jbmindustries.com/Keihin_diaphragm.html
They were too soft and would allow the slides to rise to quickly. Making her run crazy rich around 2500 rpm.
I picked up new OEM Honda slides w diaphragms and springs. (Kit #7 at local Honda dealer). Runs like a champ now. 8)
I couldnt be happier w them. http://shop.sportlandmotorsports.com/OEMpartfinder.htm#/Honda/CB360TA_(76)_MOTORCYCLE,_JPN,_VIN%23_CB360-2200001/CARBURETOR/CB360T-76-JPN-A/2Y133871AE13387116A