Multiple questions re: '81 550 front brake

So I was moving the bike outside for a good cleaning while I have the exhaust off, and it wasn't rolling as smoothly as it should. Turns out the front brake is binding. I pulled the caliper off, used a c-clamp to compress the piston a bit and it went in pretty easily. Reinstalled the caliper, front wheel rolls easily, pumped the lever a few times to apply the brake and it locked back up. So, time for a caliper rebuild. Overdue no doubt, but too many projects. Anyway I'm fighting daylight, but I figure I can at least get the piston out and see if I only need the seals, or need a piston also.

One of the nice things about a single caliper single piston system is I can just use the master cylinder to force the piston out. So I do that, until I hear pressure release around the piston, but now I'm not sure how to actually get it out of the caliper body. Admittedly I didn't try very hard, but it wasn't obvious to me.

Question 1: Should there be enough room between the two sides of the caliber body to remove the piston thru the gap? Or should the piston pass thru the circular opening on the other side of the body?

Question 2: When I replace the brake line with a new braided one, I'm considering eliminating the Y block and having a single line from the caliper to the master cylinder. Any reason not to do this?

Question 3: Alternatively, what would be involved in converting to dual calipers? I guess a different wheel, and different right side fork to carry the caliper? Anybody done this? Worth it?

My last question requires a bit of background. I'm a motocross guy, and motocross brakes have a much different feel. I'm used to having more travel at the front lever, and being able to operate it with one or two fingers. I've never really gotten comfortable with the lack of travel that street bike brake levers have, and having to squeeze so hard to engage the brake.

I read Chacal's recommendation to replace the master cylinder with one with a larger bore, but if I understand my hydraulics right that would make the lever even harder to pull. So, I'm actually considering going the other way: swapping the master cylinder for one with a smaller bore, which I'm thinking will give me an easier pull and more movement at the lever.

Question 4: Is this a bad idea? If so, why?

Thanks in advance for your replies.

 

First off, you need to rebuild the whole system, and pay close attention to the caliper itself and its "sliding pin" and holding block. To answer your questions:

1: No, it has to pass through the circular opening on the other side of the body. ***Re-assembly tip*** Put the anti-rattle spring in FIRST or once the piston's back in, you won't be able to get it in.

2: Yes, very good reasons. Chacal just explained it in another thread, I'll see if I can find it.

3: The wheel has the holes for the other rotor, they're under the star-shaped plastic cap. Yes, you'd need a different RH fork leg and a Seca 550 caliper.

"Euro" XJ550s came with dual discs, and I was considering doing it to my 550 Seca. However, once I rebuilt everything and upgraded to a full-floating rotor and stainless lines I realized it's completely unecessary. I can stand the bike on its nose with two-finger pressure; it doesn't seem like it would be worth the handling penalty because of the increase in unsprung weight just to have braking capacity that I'd never use. IMHO, it's not necessary.

Question 4: it's simply not necessary unless you go to dual discs.

 

You actually want to keep that elbow or joint as part of the system; it is hard steel and doesn't "give" at all (even the braided lines have some give to them).

Think of it this way: the ideal brake system would be nothing but hard steel all the way from the master cylinder to the calipers......that way, there would be no expansion, at all. Flexible lines have to be used in the real world. You want to minimize the use of them, though, so keep any hard steel sections (the elbow).

As an aside, the pre-production mock-ups of the XJ750 Seca models actually show a brake line system which is almost entirely hard steel lines, with just a short piece of rubber hose at the calipers. XJ750 Seca and XJ900 models actually use a lot more hard steel lines than other models (to "link" the m/c to the distro joint(s), and just like automobiles, the XJ1100 models use a hard steel line from the front to the rear (the XJ1100 models has "linked" front and rear brakes).

 

That all makes sense and I got the piston out without too much difficulty. Thanks guys.

Fitz, I know you're a 550 guy and have posted some beautiful pics of your bikes. Do the Seka's have the same bars as the Maxim's? Can you point me towards a thread that has a pic with a good view of your master cylinder?

I'm pretty sure mine is not original equipment, and I'd sure like to visually see what the orginal MC looks like and how it sits on the bars. I'm especially interested in how the bar mount aligns with the reservoir, if it's straight or angled at all, and if the reservoir winds up mostly parallel to the ground or sits at an angle.

Thanks again!