October Update,
Things have really started moving this month and progress has been quite visible, starting off with the arrival of my order from Jerry Heiden.
First up was the installation of the new alternator brushes which so far seems to have completely cured my charging issues, fingers crossed that it holds up.
Next up was a new ignition switch, I had been using a bodged switch from an fzr which I crudely attached to the handlebars, so now with the proper switch finally on hand I could install the gauges and instrument cluster.
Having the above installed meant I could get started on the wiring in the headlight bucket and see if I could get everything working correctly. Good progress has been made so far with this, I’ve had the headlight and tail light working, as well as the indicators lighting up, but they’re not flashing yet. Just waiting on some new double and triple tail connectors to arrive from eBay, and also may possibly need a new flasher unit.
I then managed to get the clutch hooked up. The side case cover was missing the clutch worm adjuster screw, however when I checked my dads stock of new parts there were two brand new screws in their packages, stapled together. I wonder why he bought two?? I know they look very similar to the valve adjuster screws, maybe he was planning on replacing one of those?? It’s a mystery!!
Anyways with that completed I just did some more tidying up, installed new air filters new bp7es sparkplugs to replace the b8es and mounted the airboxes, then routed the wiring properly around the rear of the bike.
So that brings me to the next stage, the front end……… I do need advice on this.
First up let’s talk master cylinders. My bike being a Euro 447 has a slightly different front end compared to the US models. The standard master cylinder that’s fitted to the Euro twin disk models is a 13/16-inch diameter (20.6mm). As you can see from the pic, mine is in pretty rough condition and was seized.
Upon freeing the piston and stripping the master cylinder it became obvious that it would not be possible to save it due to severe corrosion and scoring in the bores, so I just want to get a bit ahead of the game and start working out options for a possible replacement.
I’ve seen the master cylinder sizing chart posted on several threads now and the general consensus seems to be that a bore to piston ratio in the region of between 23:1 and 27:1 for twin opposed calipers is considered ideal.
Doing the math on the standard master cylinder diameter which is 13/16 inch, converted to metric gives 20.637mm
Multiplying this by π D/2 ² gives us 334.49mm².
Taking the area of the twin opposed caliper pistons as 7238.25mm² and dividing it by the area of the master cylinder gives us a ratio of 21.64:1 which is a touch outside what the recommended range should be.
From the chart a 19mm (3/4 inch) master cylinder would give a 25:1 ratio which is smack bang in the middle of the recommended range.
So I’m looking for an opinion on whether I should go in search of a 19mm master cylinder, or go for a reproduction 13/16 standard sized one? The ratio for a standard item is very close to the recommended range and from my very brief google search, there doesn’t seem to be many 19mm master cylinders in the classic style of the original.
Generally speaking, from what I have found so far, they all seem to be radially mounted items to fit modern superbikes. Obviously being a safety critical component, I am willing to compromise on the aesthetics to a certain extent.I have found some ¾ inch items that seem to have been common on old Harleys, they look the part, but there aren’t many of those on this side of the Atlantic.
Much more common seem to be Harley 11/16 inch (17.5mm) master cylinders, but this pushes the ratio out to 30:1............ I dunno am I overthinking it?? Any and all advice is appreciated, thanks guys.