Last weekend after returning from a 100 mile bike ride, I parked the NH at the end of the driveway because I thought I would have to run out on an errand later, but as it turned out the errand was unnecessary.
When it got to be bedtime, the weather report predicting rain overnight made me remember that I had not garaged the bike and went out to ride it the 60 feet from the street to the garage and started the bike as ususal.
NO CLUTCH response! I couldn't shift the bike from neutral to first without killing the engine, and couldn't restart it in gear with the clutch depressed! What ever the problem, I was glad it didn't happen in the middle of the 100 mile ride.
So, the NH sat unused all week and I drove the van to work. Yesterday afternoon, I decided I better get diagnosing what was wrong while it was still daylight if there were any chance of riding the bike this week before the cold weather starts to set in... So I went to the garage and put the bike on its center stand, covered the gas tank with plastic to protect it from any brake fluid that might stray from where I needed it, and removed the cover on the clutch master cylinder reservoir...
It was empty! 
I checked the sight glass in the front and it still looked like it had fluid, but that turned out to be a dirty sight glass window!
SO I was sure I had air in the system.
I decided that since the master cylinder had sludge in the bottom, that my best bet was to remove it from the bike and disassemble it to make sure it didn't also need to be rebuilt. My search of the forum gave me the confidence to attempt to do this... something I have never done before. The only tools necessary are the right size socket head allen wrench (8mm) and something you can live without but I am so glad I had picked one up a couple years ago at a parking lot sale: A since cheap chinese set of snap ring or circlip pliers. You may be able to get that snap ring out that holds in the piston without a set of these BUT I DON"T RECOMMEND IT!
There are plenty of threads give the specifics on disasembly and bleeding. A few minutes later, using DAWN grease-cutting dish washing liquid soap and really hot water, I had the MC apart, and tooth brushed the sludge out to find that the cylinder was not scored from the sludge. My digital micrometer verified that the piston was still within specifications, and the rubber piston components looked good. Some compressed air removed any trace of moisture from the assemblies and it was time to put it back together.
I had an old bottle of DOT 3 fluid that I used to coat all components before assembly, but I had a new bottle of DOT 4 brake fluid that I had purchased right after I got the NH because that is what is specified on the top of both the clutch and brake master cylinders lids.
Once on the handlebars, I put my thumb loosely over the opening where the banjo bolt attaches the brake line to the MC and covered that hand with a rag, and slowly pumped the MC once. Air and fluid came out, and I then sealed the hole with my thumb and released the lever slowly. I repeated this three times and then refilled the reservoir.
Then I reattached the brake line loosely to the MC, and repeated the procedure (also covered the fitting with a rag to catch any fluid spillage). After what appeared to be three successive squirts from the loosely attached fitting, I tightened the connection confident that I had removed most of the air from the system. I refilled the reservoir one more time and then slowly tested the lever and I had "some" resistance... so I knew I was making progress!
Then I found an 8mm box end wrench and carefully loosened the bleeder screw on the slave cylinder. If I had more time I would have removed the slave cylinder and cleaned it as well, but I didn't have much time so I decided to just bleed it and see what the results were. I took the clear plastic hose (6') that I had purchased weeks before because I saw it on sale, and attached it to the slightly loosened bleeder screw and watched carefully as I sucked the other end. About 6 inches of dark fluid filled the hose followed by fluid that was getting cleaner!
I followed standard bleeding procedure and closed the fitting and dumped the brake fluid I had removed into my waste oil container. I repeated this process three times, while carefully watching both the hose and the reservoir until I was getting no bubbles, and then tightened the fitting.
I carefully squeezed the lever and TA DA! I had what felt like good clutch resistance! Three dollars worth of hose, and four dollars worth of new fluid and an hour of my time and I could ride my bike again!
What a great feeling not to have to take my bike somewhere else and have some moron charge me a bundle of money to MAYBE fix my bike.
Next challenge will be the BRAKE master cylinder! Whne the riding season is completely over... in the mean time, I made SURE that the brake MC has a full load of fluid!
BTW, I am sorry there are no photos, but with my hands wet with brake fluid at different times, I didn't think it was a good idea to be handling my $400 camera... maybe on the next repair.
Thaks to all who contribute to this forum. I hope my description of this process helps somebody else keep their bike safely on the road.
Happy Trails to YOU!
