TOPIC:

wrenchmonkey wrote: Just thinking out loud here but you asked so:
Is it possible that your rear master cylinder is simply too small to move enough fluid for two calipers?
Since you said it works find on the original setup which I am assuming was just one caliper on the rear and you've gone through a litre of brake fluid already... There's not much more of the dark arts left to consider.

I may stand corrected here but when the front end braking system changes from a single caliper to twin caliper, I thought the front master cylinder also changed to a larger bore based on the second caliper having the same size piston as the first.

KZQ wrote: I've run into a road block while working to hook up the brakes.
...
I tried reconnecting the master cylinder to the original rear wheel which is still complete with the disk and caliper. I was able to get good pedal after only a very brief bleeding effort, so I know that the master cylinder is good.
...
At this point I've wasted a liter of DOT 4 fluid and accomplished nothing.
I'm open to any suggestions.
Bill

Thanks WM,
The master cylinder is a 5/8" diameter unit. I believe it's as large as they come. I've done some searching and am now suspecting that I'm going to have to reroute the hoses so that I can lift the cylinders to be higher than the the tee fitting while I'm bleeding the system.
Thanks
Bill

I hate brake lines there always seems to be that one bubble that hangs on.
This may sound weird but maybe you could try using something that vibrates to move the bubble along
Like a palm sander.
I never seem to get all the air bubbles out until I take the first ride.
Instead of trying to push the bubbles down to the caliper , try to vibrate them up to the master cylinder
Also I have been priming the hoses with a syringe filled with brake fluid the last couple times and it seems to help

you can always use a lil pump oil can(that you buy just for this that never had oil in it) with brake fluid in it and a piece of vacuum hose clamped on and up bleed them back to the master cylinder.pop the hose on the bleed and crack it and go to pumping you will have to mess with the lever to find the spot it bypasses back to the cylinder but it works nice.
hth,
leon

I ended up having to disassemble the whole thing so that I could get the calipers at the top of the system. With gravity working with me I got it to purge. Unfortunately, Now that I cannot run the hoses as I wanted (they have to lay on top) they no longer work for length. I just now ordered a two line system with a double banjo bolt. Hopefully with the "T" eliminated the simple lines will not trap the air.
Oh Well. The Joys of Custom Work.
Bill

Keep up the good work Bill.

If it was easy , everyone would be doing custom work

Dave

What diameter line were you using? A coworker made the mistake of using oversize lines on his van and could not ever bleed them. I think he had to re-do all the lines with a smaller diam.

Hi Lou,
These are good quality Galfer stainless steel lines. I'm not sure of the ID but the OD is 1/4"

I ordered this dual line kit :



Without the TEE fitting I hope to have no further problems bleeding the system. The hoses them selves are too small to trap air and the only other place that might is the double banjo bolt and that'll be easy to bleed.

While I'm waiting for the brake lines I went back to work on the drive line. I had failed to consider how one might add a master link to an RK O Ring chain. The answer is you can't, not without a special tool to press the side plate onto the pins. I decided that the rivet style master link was the only safe way to go so I dumped another hundred on one of these:




Once I had the chain cut and installed I lined up the sprockets and welded the pinch blocks to the axle tubes.
The next project will be the exhaust system. I cut the stock mufflers (they were rotted out) off of the head tubes and bolted the head tubes up enough to see that a two into one configuration with the muffler on the right side will be the way to go. I've got a line on some 1 3/4" stainless tubing. The vendor has "J" bends although I'll have to weld up my own "Y".
Wonder If it'd be worth it to pick up another MAC system and modify it so that the megaphone lays level?
Bill

i think keeping the muffler level will be the most aesthetically pleasing

leon

531blackbanshee wrote: i think keeping the muffler level will be the most aesthetically pleasing

leon

Thanks Leon! Yeah the axle running across there makes it a necessity. I'm in Vail, CO until Thursday evening. I'll get some more picks up this weekend.
Bill

Even though I haven't yet made up my exhaust system I couldn't resist and went out for my first ride today. I learned quite a lot. Head pipes are LOUD. I need a stiffer front fork. Also need a steering damper if the new fork can't give me less trail. I also learned that I need a larger rear master cylinder. The 5/8" unit that came on the bike just can't handle the four pistons on the back brakes. Any body have any suggestions?
When one of the rear tires goes over a bump the roll on the frame causes the front end to wobble. Even though I was only going 20 MPH I could feel a harmonic tank slapper in the making.
My Wife shot some video:

Bill

Would lowering the rear help?
Steve

swest wrote: Would lowering the rear help?
Steve

Lowering the rear would increase the trail. How would that help?
Bill