Integrating front and rear brakes

[John]

XJ brakes

Garry,
I have sent Gregg the XJ brake hardware to install on his 79XSF.
He wants to try to connect all three calipers to the XJ rear master cylinder. It will be easy enough to do, he can just use the front brake junction block located on the lower triple clamp. He will just need to remove the hose leading from the front m/c, and attach the line from the rear m/c to the same place the front one came from. If he wants to use the XJ set up (rear m/c to l/f caliper) he'll need to change out the junction block to the XJ's. I agree with the pressure increase with three calipers in the circuit, but I'm concerned that the m/c will not be able to move a large enough volume of fluid to (I'm at a loss for the correct term) overcome the small distance that the pistons retract back into the caliper bore when the brakes are released. Does this make any sense? I'm not trying to start a 'pissin' contest here, just voicing my concern over trying to link all three calipers to one m/c. It may work. I've been wrong before and I'm sure it will happen again, more often than I would like. Let's wish him luck, and help him out if he should ask for it.

[TheDjost]

We all can argue all we want, but the only way to be sure (except for a fluid dynamics engeneer or hydraulic brake design specialist to jump in here) is to wait for a report from Gregg who is going to try it.

My vote goes to the "It's going to work" side.

-Justin

[mitch]

Right on

We will all know soon, be careful when you first try her out little buddy, and if it works well plse let us know................MITCH

[chevy45412001]

I was just thinking, that if he puts all three brakes on ,then bleeds the system,there should be fluid enough to apply the brakes.As all three calipers will be full of fluid,not air. Just my thoughts.

[fusionking]

Hey John I ditto your comments! My 2 concerns are (1) it could be possible later with wear and all that he will need to keep a close eye on freeplay and rotor runout. Also (2) front brake lockup when you least expect it. I really can't piss very far (or accurate these days) I think it will work. I would use the entire XJ set-up tho cause it was engineered to work correctly but that is just me. You seem like a very nice and generous guy and I hope your stuff will get him headed in the right direction and he can enjoy his bike as much as the rest of us!!!!

[John]

Thanks Garry

Like I said, I wasn't trying to start anything with anybody. I just wanted Gregg to be aware of what may happen with all three calipers on one m/c. I was thinking of doing the same swap at one time with my 80SG, but laziness, and not wanting to spend any money to rebuild the m/c stopped me.
I do have a little expertise in this field. I was a hydraulics tech in the Navy, and I'm a ground equipment mechanic for American Airlines now, and have been for 18 years.
I hope he has good luck with it, as I think it will be a precedent, I believe.

PS Were you serious about swapping an XJ alternator on to your XS? I had thought about that also when I swapped out the original engine in my bike with one from one of the XJ's that I'm parting out. I also wanted to swap ignition systems, but nobody, at the time , had a schematic that I could study to see what I had to change in the wiring harness. It should be an easy swap, providing I had a print, but I sold the boost sensors that I had, and they are neccessary in the XJ ignition system.

[tctenng]

Got the part today !!!! Doesn't look like too tough of a job. I think I will get some SS lines made up at a local shop as suggested. The parts are in great shape. I have torn down my front end to clean out the calipers and replace the fork seals and change the oil. Have a little delay in putting back together as the seal I bought are the wrong size and I have to get replacements. I will keep the thread posted as I get everything installed and tested.


Gregg

[John]

Gregg, I see you got the parts ok. I'm glad you're satisfied with them. I would recommend that you clean the m/c with rubbing alcohol. I've read that it will absorb any moisture, and evaporates without leaving any residue. That's what I use on mine and my wife's bike. I just remove as fluid as possible, and then drain the lines by opening the bleeder screws. Then I fill the m/c with the alcohol, and proceed like I was bleeding the brakes. After cleaning , just refill the m/c with brake fluid and bleed the s#!t out of them. That will chase the rest of the alcohol out of the system. Are you still planning on linking all three calipers to the rear m/c? As far as the fork seals go I would recommend OEM Yamaha seals. I have tried many different aftermarket seals, and none of them lasted very long. With the OEM seals, I haven't had any trounble in over two years, and I can pressurize the forks to 12 psi with no leaks.
I didn't mean to start a pissin' contest over the use of three calipers at your expense. I was just voicing my concerns , and didn't want to see anything happen should it not work properly. Good luck with the project, and keep us posted.

[fusionking]

John....I would love to upgrade my alt. but money is sorta' tight at the present and mine is workin' good for now. I do want to do this if I don't have to be an electrician to get it going and it would be a worthwhile endevor. Just curious.....how much would it take for you to part with it? Kind'a funny huh...talkin' alternator stuff on a brake thread!

[jkgrubbs]

Stoopid Question, and I know I am getting in on the discussion
late, but.....for future reference for myself

Am I missing something? My 81 midnight has a linked brake system. The foot lever does the rear and left front, while the hand does the right front disk. Would not this setup be the easiest way to accomplish this endeavor?

[mitch]

!st THREAD

JK you need to go way back and read the 1st thread...MITCH

[jkgrubbs]

like i said, stoopid question.

but i guess i meant to ask if getting parts from an xs series with a linked brake sys would be easier than from an xj, or are the parts between the xj and xs that similar, as I am not that familiar with the xj, and admittidly I am at the end of the conversation and only ask because I don't know.

thanks, and I hope it works well, Gregg

[John]

Linked brakes

JK, Are you sure that the linked brake on your Midnight is original? I ride an 80SG,and mine doesn't have it, and there is no mention of it in my Clymer manual. Could be that you have a bike that someone modified? A quick way to check would be to look at the frame rail on the right side near the master cylinder. Is there a bracket on the frame rail for the junction of the hose and steel line to bolt to? There is one on the XJ. I'm not too familair with the LH, so it may be possible that the brakes were linked.

[jkgrubbs]

John,

I am reasonably certain that it is original, the install looks too clean. I have had the bike two years, and done some work, mainly brake pads, smoothing running issues carbs/jets/kerker. I went to look just now, so that I am sure, but the rear master cyl has a valve (proportioning) bolted to the back, which feeds two brake lines, one to the rear caliper, and one towards the front of the bike. The one towards the front goes up the spine to a junction block behind the YAMAHA plate on the forks, then feeds the left caliper. The hand does the right caliper. There is a small bracket on the tube coming down from the side cover, just in front of the swingarm pivot, that is currently empty, that looks like it was a post that held a rubber grommet. If anyone knows what it was for, please let me know This is the reason for my asking the question. I am not that familiar with the standards, and knew that the only bikes that had linked systems this old were the Yamaha, some Guzzis and BMWs. I now understand that Gregg wanted to link all three calipers, and am waiting to see how he did. If anyone knows more of this mystery, please chime in.

[mitch]

linked breaks

1981 was the only year and the midnight was the only xs that had linked breaks from the manufactor. then from 82 to 84 the xj retained that system........MITCH