Rebuilding the master brake cylinder

 The bike came with some temporary small chinese master brake cylinder. It did work but the braking power was minimal. I guess putting my foot on the asphalt would have the same braking power...

 

Honda CB500K1 temporary master cylinder

Luckily the old clogged up master brake cylinder came as a spare part with the bike. It was completely stuck and was in desperate need of a rebuild.

Honda CB500K1 master cylinder

 

Honda CB500K1 master cylinder exploded view

 

So I bought a rebuild kit for around 25 dollar from 4into1.com and started the rebuild.

It looks easy but it can be a real pain to get all the old rusted, clogged parts out of the mater brake cylinder.

The biggest challenge was to get the retaining clip out. It sits quite deep in the narrow shaft and most tools are too fat to reach it. The best option is to use a pick or similar. For more than an hour it wouldn't move even a nano inch but then all of a sudden it snapped into 3 pieces and I finally could take it out. All the other pieces are now easy to remove.

Honda CB500K1 master cylinder old bits

I gave the master brake cylinder a good clean and sanded the inside with 240 and then 400, 600 grid and finally some steel wool to get rid of most of the corrosion.

The rebuild kit comes with some red grease which should be applied to the new rubber bits. Of course the new retaining spring gave some trouble... I pushed it in all the way with a long socket that just fits inside the narrow master brake cylinder entrance. There's a small groove in which the clip should click in.. It looked like it clicked in the groove but apparently  it wasn't and everything got stuck inside, grrr...

Honda CB500K1 master cylinder rebuild kit

Honda CB500K1 master cylinder rebuild

 

After some trial and error ther clip came out and in the second attempt I managed to get it click into its groove.

I also ordered a new cap as the old one was faded and damaged on the outside, and of course a new diaphragm. The plastic ring that goes between the cap and the diaphragm was still in perfect condition so I reused it.

Another little thing I had to replace was number 11 (part 45526-341-000) in the exploded view. It's a rubber/plastic tube and a piece of fishtank hose was a perfect fit ;)

Honda CB500K1 master cylinder bush 45526-341-000

Honda CB500K1 master cylinder rebuild

All done :)

Honda CB500 K1 1972

Back in the nineties I used to own a couple of SOHC Honda bikes from the seventies. All sold but still in my mind I started looking for a nice CB project to help me through the dark winter evenings. Browsing internet for a Honda CB I came across a 1972 Honda CB500 K1.

Honda CB500 Four advertisement

Honda CB500K1 1972

Honda CB500 K1 1972

Honda CB500 Four

The bike had been sitting in a shed for well over ten years and the engine was stuck from doing nothing for all those years. It came with a 4in1 exhaust and a poor quality custom brushed on paintjob but besides that it was almost a 100% stock original bike.

I've always liked the early CB500 bikes and as I was looking for a winter project I decided to pick up the bike as it was only a 1200 km drive (one way). It was a fun roadtrip with my bestie Batty over long flat roads across the middle of nowhere. No signs of life except for kangaroos, emus and speeding roadtrains.

The bike was as advertised and came with some original spare parts. Another nice surprise was the original owners manual still sitting in the seat and the stock airbox filter and toolkit tray were still there.

Honda CB500K1 owners manual

Honda CB500K1 owners manual

Pick up Honda CB500K1 with my Mitsubishi van

Back home I started cleaning the bike, there was a thick layer of greasy dust all over the bike.

Honda CB500 waiting for some TLC

Honda CB500K1

After changing the oil, oilfilter and adjusting the tappets and ignition timing I tried to start the bike. It made some pops but would only run for a sec after spraying starter fluid in the original airfilter box. When I inspected the leaky fueltap I found out it was almost completely blocked with dirt and tiny rust particles.

So I quickly made an external fueltank from a big syringe :)

 

Syringe fuel tank :)

Auxillary seringe tank

After some more kickstarting (the way too small battery in the bike was almost flat) the old Honda CB500 came back to life.  

                                                                   Honda CB500 K1 running

 

It probably needs a good carb clean and synchronising and some new sparkplugs but I was really stoked with the fairly easy but big progress.

Honda CB500K1 1972

 

Now I know everything is working it's time for some resto :)