Yes
I converted my /78 R80/7. I punched the motor out to 1050cc, dual-plugged, cammed, lightened and balanced everything, and suddenly required brakes that worked.
I bought the lower fork legs, brembo calipers and master cylinder unit off an '82 R100RS and bolted it right on.
Then I discovered that the brembo calipers would not clear my custom stainless steel spoked rims, (or any spoked rims for that matter) so I could either shop for a pair of used snowflakes or take the brembos back off. I had spent a ton on the rims and nobody wanted them so I took the brembo/legs off and went back to the ATE.
Of course, I knew the master cylinder wouldn't match up. It felt a little firmer than the original under-seat remote master cylinder (stainless brake lines added too) but since the piston stroke was designed for the dual piston brembos, the brake lever had way too much travel. I was getting discouraged, and research said I could modify a brand x Master cylinder and change the controls etc., etc., but I just decided to live with it for a while.
Concurrent with this, I put meonite (I still don't know what meonite means) cast iron rotors and ferodo pads in place of the stock. They stopped better, but the cast iron rotors immediately warped....They were cheerfully replaced and immediately warped again. At this point I was sick of the hassle, just wanted to go for a ride and had finally saved the cash for a brand new 16valve/abs/krs (with floating discs) and said screw it.
To be fair, it was pointed out to me that the next step was to rebuild both calipers to be certain that they weren't dragging, causing warpage from overheating, but I never felt any unusual amount of heat on the discs, both were warped, and so I opted not to.
I had to knock $300 off the price of the bike when I sold it so the new owner could go back to stock brakes.
Obviously, it is important to do just what you are doing, make sure all components match properly before you pop those $$. Other than my few fatal errors, I would have benefited from the project.
IMHO.....Adding another disc will increase your stopping power dramatically, but cast iron may be an uneccessary additional expense and hassle.
Maybe others out there can provide more data on the cast iron rotor issue, my results were pretty unhappy.
David Owen
dowen@westmx.westmont.edu
'92 R100GS/PD