Various Tips for bleeding linked brakes... from the GuzziTech.com webboard.
First, make sure the return orifice in the m/c is open.
Then, position the m/c reservoir so it is as nearly level as possible. This is so the air that you will "walk" back up the lines will purge out through this orifice, rather than hanging up inside.
I then fill the res., take out the bleeders on the calipers, wrap them with teflon tape, and thread them back in but not closed tight. Hook up a vacuum pump to the bleed nipple and apply some suction. Squeeze and hold the brake lever for a few seconds. Do this a couple times, and the fluid will begin to flow. Be ready to add juice.
When it stops flowing, take the handle of a crewdriver and tap smartly on the caliper and along the line all the way back to the m/c. QUickly pump the handle and hold it back. Use quick pumps, rather than slow squeezes becaquse this breaks the bubbles loose and forces them to move.
You'll likely see a long string of air bubbles burp out of the return orifice in the m/c. Pump and hold a few more times till the bubbling stops and fluid starts to flow again. Fluid will likely be bubbling out of the caliper by now. Keep adding vacuum, new fluid, pumping, and tapping as necessary.
Close the bleed nipple when you start to get some movement within the caliper. Pump the brakes 10 or so times and hold the lever back while you tap again along the caliper and line. Watch for bubbles through the return.
Pump it 10 or so more times and hold while opening the bleed nipple. Watch for bubbles. Leve the bleeder open (with the vacuum line still in place), and pump violently until the bubling subsides. Close the nipple, pump up again, and repeat this purging and the tapping till it feels solid.
I have never had any problems bleeding the brakes on any bike I've owned, including ABS equipped ones, nor on any car. Here's what I do, nothing fancy, nothing hung upside down from trees or anything like that.
1. Bleed the master cylinder first. If you don't do the MC first you can spend the rest of your life at the caliper and get absolutely nowhere. Bleed it by loosening the banjo fitting while the MC is under pressure. Tighten, pump, crack it open, and repeat. Make sure you have a rag under the banjo bolt because it is very messy. Do it 5-10 times.
2. Bleed the brake caliper that is the FARTHEST away from the master cylinder. ALWAYS start on the longest line (which is obviously the one farthest away). Use a piece of clear rubber tubing over the bleeder nipple so you can see the bubbles come out. Make darn sure you always have the system under pressure if you have the nipple loose. Don't believe any charlatans who claim you can release the lever/pedal and get multiple pumps if you have said hose on.
If you want to get really adventurous, you can bleed the brake line before you do the caliper using the same technique you did on the MC (I just put new SS lines on the SPII and didn't do this though). Greg F, I suggest you do this as it might get some air out of the lines before it gets to the caliper.
3. After you get the far caliper done, then go to the next farthest away, and so on finally doing the nearest one. Make sure you don't let the MC get even close to out of fluid or you will have the pleasure of repeating this whole business.
Adding one more thing after re-reading Greg's post; bleed the proportioning valve (or just a block in '76 IIRC) too. I would do this.
1. bleed the m/c
2. bleed the proportioning valve, all three fittings starting with the input
3. bleed the line at the caliper
4. bleed the caliper
There is a procedure for priming a new MC but I can't remember it exactly. If you need me to, I'll try to dig it up. Basically, you bleed it "on the bench" before it's connected to anything else to prevent it from pushing all that air down the line.
The only hard thing about bleeding brakes is doing it by yourself if you aren't a contortionist.
My approach for what it is worth is to reroute the brake lines along the lower frame rail the master cylinder - I connect the front caliper using a long peice of Aeroquip (I use the rubber coated stuff which doesn't saw through everything it touches) which is zip tied up by the steering head. When I bleed the brakes I undo the zip tie and let the line flop down when I bleed the brakes. I have found the brakes bleed dead hard in about 5 Minutes this way by gravity.