Glad to have your questions & for some reason i seem to be finding them 1st to be the one who is answering, so if any one else has better suggestions, let's hear from you !
Glad you were able to get that screw out of the master cyl !
Carb kits - i have used the Keyster kits out of Canada, from - Sirius-Consolidated, they have them for sale all the time & now - Ebay # 4542901453. They seem to work fairly well, i don't think the quality is as good as original Kehin parts, but Kehin parts are EXPENSIVE. I have encountered poorly machined float valve seats that leak. Otherwise the kits are very good overall. Really, i don't feel, other than new gaskets and needle, any other parts need to be replaced.
On the sticking caliper piston - i don't know any way to reliably & effectively make it not stick without dismantling the caliper - not a big job, just takes a little time. The sticking is caused by old broken down brake fluid that over the years has absorbed moisture and other contaminants from the fluid/water in the rubber hoses & against the aluminium, then collected around the piston/cylinder seal, causing the piston to stick & not retract, in turn not allowing the brake pads to float away from the disc. I would suggest, since you are rebuilding the master cyl, rebuild the caliper as well, get the caliper seal from Honda (or K&L). This is the only part that probably will require replacement - unless the piston has corrosion that cannot be removed or pitting. Just gently use a green abrasive pad on the piston & inside of the cyl to remove all contaminants, etc. Then you should be ready to reassemble the caliper and charge the system with new fluid. Always a good idea to replace any of the crush washers joining hoses to brake parts as well as purge the hoses of the old contaminated fluid. I wash out the hoses, junction, other parts using a copious amount of brake cleaning fluid til clear followed by compressed air.
