Topic: questions for anyone running dual disks on a 550...

[paulages]

probably applicable for 750s too:

how does the brake lever feel?
how improved is your braking?
is anyone running two disks with the stock master cylinder?

i put about 230 miles on my bike today, after adding a right side disk yesterday. i have SS lines, a stock master cylinder, and am splitting the line where the bottom half of the line connects at the T in the steering head, using a double banjo bolt. i bled and bled and couldn't seem to get all of the air out of the lines, so i finally decided to go for the "self bleeding" method---just wiggling the lever a lot as riding vibration gets air bubbles worked up through the system.

so now, after riding to the top of mount st. helens and back all day: i have braking like I've never had before, but the lever can still be pulled all of the way the the grip. when actually stopping, it doesn't go anywhere near that far, and in fact feels effortless compared to the stiff brakes i had two days ago. it feels soft in the way that car brakes do...soft, but effective. anyway, i plan to get all of the air out one way or another, but i just wonder what other people's are feeling like. sure is nice to be able to stop well!

[Short Round]

what kind of disks and did you go with the stock calipers?  I was thinking of doing the same thing to my  550.  let me know exactly what you used .  You might want to get two other people to help you with the bleeding.  Two turning the bleeder valves and one pumping the lever.  Just a thought.  Let me know what you used. Thanks- Chris

[paulages]

yes, stock disks and calipers. unfortunately, i was by myself when bleeding, but was using clear tubing over the bleed valves and it was certainly (large) air bubble free. the new caliper flexes visibly when the lever is pulled, and i believe this may account for some of the give in the lever, but there has to be air in the lines still. i'll hunt down speedbleeders this week...

[eurban]

The stock single disc master cylinder does not really have a large enough bore to give you a good lever feel with dual discs.  Too much lever travel for stopping.  Also the stock single disc  front setup can have a good bit of slop, both at the brake arm pivot and as a result of the gap required to keep the fixed pad from contacting the rotor except during braking.  These may be doubly be conspiring to soften your brake lever feel.  You should be able to get all the air out of the system with proper bleeding (a buddy would probably be helpful) or using a vacuum type bleeder (Mityvac etc).  In the end you may or may not be OK with the stock MC but if it was me I would find a master cylinder sized for dual discs.

[bryanj]

Get a GL 1000 master cylinder if you want it to work and look the same. You will never get a good feel with the original master as it just dont push enough fluid

[paulages]

thanks for all the advice. yeah, i know that everyone says to use a gl or some other larger-bore master, but i figured i'd give it a whirl first. i did tie the lever down the first night...the second disk may be new, but it sure aint the first time i've had to bleed one of these. 

i've yet to find a larger bore master that i think looks as good as these in keeping the vintage look. i have been looking for a 750F master though, as it looks almost the same but has the bore intended for a dual disk.

oh, and like i said: the lever doesn't actually have to travel far to make the bike stop, it's just that it can go farther once it has.

[jph550]

I'm running a stock master cylinder on my dual disc 550 set up and do have a soft lever feal.
I plan on hooking up a bigger master over the cold months. Bleeding these has been a problem for me too. I never can get all of the tiny bubbles out.
So, I got some speed bleeders. Makes it a little easier, but doesn't make the lever firm and speed bleeders don't seam to work well with a vaccuum/mighty vac bleeder system.
I still can't get all the tiny bubbles out, even with the speed bleeder.
I just ordered some original brake valve bleeders from Honda and am going to try the mighty vac way again and cycle a lot of fresh brake fluid through the system and see if that helps.

I imagine once I put the bigger master cyclinder on her the tiny bubbles won't matter as much any longer.

peace

[bryanj]

If you get the master from the first two years of GL 1000 it looks exactly the same as the 500 just has the bigger bore, its the later years that have the tall see through reservoir.

[eurban]

Bryan-

I haven't seen a GL master cylinder that didn't have a plastic resevoir.  The one that came with my 76 front end had a round plastic resevoir.  I wanted the look of an all aluminum resevoir so I used a 77F one that was sized for the dual discs. . . . .

[bryanj]

Very first GL 1000 (K0-75?) had the all black cylinder and  here in UK so did the next year as well. Cant remember after that. First one i remember with the plastic reservoir was the KZ which was the first black colloured one. If you find one of the original red or blue it should be the same as "ordinary" 500/750 I can give you an original part number if you want.

[chippyfive50]

I can't say enough about the 7/8in NISSIN master cylinder($129)  i put on. I also went with 750 disks. I currently only have 1 of them hooked up, but it is worlds better than the stock setup, smooth and firm and tight the only way!

[eurban]

Bryan-  Must be a UK thing with the full aluminum MCs on the GLs because even the 75s here in the states have a round clear plastic resevoir. I know because I rebuilt the GLs master cylinder before I decided that it wasn't nice enough looking for my project.  Parts pages show the plastic resevoir for the 75 and 76s.. . . .

[bryanj]

When i wanted one, years ago, Girling was importing some and i got one of those. Having said that i just looked in the parts book and it shows the two part with clear reservoir, go figure, perhaps the clear reservoir is all that is available now and is a retro fit to the earlier.

[Dennis]

I'm running a stock master cylinder on my dual disc 550 set up and do have a soft lever feal.
I plan on hooking up a bigger master ........
 I never can get all of the tiny bubbles out.

I imagine once I put the bigger master cyclinder on her the tiny bubbles won't matter as much any longer.

peace

Just remember that the m/c piston must travel 2X the distance to work both calipers. It must move twice the volume of fluid so it will never have the same "feel" as with one caliper.

As far as the tiny bubbles are concerned, bubbles are bubbles. The volume of air will effect your braking.

[paulages]

okay, another question for anyone else already running this setup:

how did you align the right side brake hardware? i mounted mine just like the left side, but as far as i can tell, the new disk doesn't seem to align to the same point on it's mating fork. everything works fine...no dragging, and it stops. but if you squeeze the brake lever, you can watch the caliper twist as it grips the disk, as if the pad was angled and it was straightening out. not like the subtle movement that normally happens when the pivot arm moves to allow the caliper to grip and release. this actually pulls the disk just a hair to the outside, resulting in a very slight pull when i brake.

any pics anyone?

[bryanj]

l, did u fit new pads to both sides? I did this years ago and didnt notice a problem. I will be doing another one next year. I would suggest spacing the bracket with washers

[paulages]

i've avoided posting about this actually, until i got a new set of pads for the new side. the old ones weren't very worn, but they were definitely old. they didn't seem to be bevelled. we'll see if that fixes it...

[cben750f0]

http://www.sohc4.us/forums/index.php?topic=2582.0

 here is a document i wrote on the double disk set up... hope this helps, shoot me a pm if you need more help...

peace