Things are moving along. As per my previous BLOG entry, I have the rear wheel and disc brake assembly, exhaust, and a dummy engine fitted, and have been looking at options for fitting the rear master cylinder and its brake fluid reservoir. Space is tight on the right side of the frame due to the injector oil tank and also just the way the frame is designed.
I was originally thinking of using a long link from the underside of a modified brake arm, to a remote mounted master cylinder as per the photo to the left. There is enough space to run the link back from the underside of the brake arm, under the frame member which supports the rear passenger foot rest and exhaust pipe mount, to the clevis of the master cylinder, as the Gibson pipes allow quite a bit more room that the stock Suzuki exhaust. After discussing this with a few folks in the local Rocky Mountain CVMG chapter, and looking at a bike here in Calgary with a similar conversion, as well as searching the web for photos of other completed rear disc conversions on GT750’s, its obvious there is no ‘right’ answer as each one seems to have been done differently. For my conversion, I’ve decided to use a mechanical linkage from the existing stock rear brake pedal, to a bell crank which will be attached to the master cylinder. This installation has the benefit of preserving the same ‘period look’, preserves the stock mounting for the rear brake light switch, and also gives the same mechanical advantage to actuate the braking action as is found on the 1976 GS750 that I’ve been using for donor parts. Preserving the same mechanical advantage will ensure maximum brake pedal effect on the master cylinder, which is not a bad thing when you are trying to stop ! You can see the mocked up installation in the photo to the right.
The linkage is salvaged from an old CB350 Honda front brake assembly and the master cylinder and remote brake reservoir are off a 1980 Suzuki GS750EC, all of which I found at TJ’s Cycle, I cleaned up the surface rust on the linkage with that old standby – Coca Cola (traditional, not the diet version !) – and it now looks quite nice ! To ensure sufficient clearance between the master cylinder and the swing arm, I will need to modify the injector oil tank reservoir slightly, or use something off a different model of bike, or possibly just make a new one as I want everything to fit properly under the stock right side cover. The plastic used in the stock injector oil tank is soft – possibly ABS or perhaps a urethane. In any case, with a bit of luck (and a lot of cleaning !) I should be able to solvent weld it using one of the newer adhesives on the market used for automotive repairs, or possibly just deform it as required using a heat gun.
I’m pretty much at the point where the next step will be to get the frame and fittings welded up, after which I need to strip the frame and swing arm down for painting.
The ‘home’ site for the project is here. Till next time ……….