I've searched around quite a bit on this one and I am coming up empty, so looking for your thoughts on this.
The best I can figure is that my new Nissin m/c piston is possibly not the right size for my calipers to get the brake lever feeling and likely stopping power I'm hoping for.
Bike:1978 Cb750F
Dual disc brakes -38mm caliper pistons
Original M/C is 11/16" piston
New parts:rebuilt calipers all new rubber
new caliper pistons
new braided SS lines
new banjo bolts
new master cylinder Nissin 14mm piston - 17652B
Issue:I've bleed the brakes substantially and still have a rather soft feeling brake. The lever does build up pressure and pumping it doesn't really seem to build up more pressure like it typically does if more air is in the system. But with a fairly firm grasp, I can bring the lever back to touch the grip. To me, it just doesn't seem to get firm enough through the lever travel. I took it for a test drive and it does stop alright, it just doesn't leave me with a lot of confidence. Especially, since I changed out and replaced so much stuff. Am I expecting too much?
The best I can figure is this: 1. my new M/C piston size is not an appropriate size or stroke length to create enough pressure
2. I'm expecting too much from this rebuild and the new parts.
From what I gather from the somewhat hard to understand doc that I see linked to a lot -- (
http://www.vintagebrake.com/mastercylinder.htm) -- My M/C piston to caliper piston ratio would be this:
Original -- 9.43:1 (38mm caliper pistons and 11/16" or 17.5mm M/C)
New -- 14.73:1 (38mm caliper pistons and 14mm M/C)
I'm mostly confused by the doc because my ratios are completely out of anything he recommends or mentions. So it was not intuitive the first several times I looked at it.
Looking for some thoughts or advice. Unfortunately, the brakes were in a rough state previous to my rebuild, so I don't have a good knowledge of if this is better or not. I'm just missing that firm feeling of confidence when I squeeze the brake at the lever. Granted that doesn't always necessarily transfer to awesome braking power.
My other bike for instance, a 2000 Suzuki Intruder 1500 cruiser, has about 1.5" of soft play at the lever, then a firm contact feeling to the point of where it would take two hands to pull it to the lever. With this setup on my CB, I can get it to the grip with less effort.
Anyway, would appreciate your thoughts on this one.
