another front brake question

[spiney]

1981 R65 silver twin ATE callipers square reservoir 15mm master cylinder and calliper kits installed.  Disc will only stop if I pull handle quickly. Pull handle in slowly comes all the way in disc spins freely? Any ideas?

[Bob_Roller]

Have you bled the brake system ??
If that isn't the issue, sounds like a master cylinder problem .

[spiney]

Have you bled the brake system ??
If that isn't the issue, sounds like a master cylinder problem .

Thanks Bob, yes bled correctly using a venturi/compresser bleeder tool. Pretty sure there is no air in it.

[Tony Smith]

If there is no air in the system, the only thing that can explain your circumstances is a faulty master cylinder.

By the way, 15mm is way too big for a pairof ATEs, 13mm would be much, much better, I have bigger diameter caliper pistons that you (ex-K100 brembos) and run a 12mm master cylinder.

If it transpires that you need to spend money on your master cylinder I might be interested in buying it from you as-is as 15mm would be about correct for the Brembo 4-spots I'd like to try.

[spiney]

Thanks Tony will keep you informed on what happens. the bike as far as I know is original it has 15 stamped on the master cylinder. The callipers I am told are a little unusual, one bloke told me he has seen cllipers exactly the same but stamped Brembo. Munich Motorcycles when they sold me the kits said they have seen the silver ATE calliper twin disc in models imported to Australia.

[mrclubike]

Sounds exactly like a master cyl issue

[spiney]

From OEM parts 32 72 2 302 370  CYLINDER WITH PISTON - D=15MM (from 09/81) 0.41  1   $191.72

The bike is a 12/81

[ged in oz]

Did you already put a rebuild kit through the MC?

Was the MC working ok before you fitted the calliper kits?

The symptoms sound like a rubber seal issue somewhere. It sounds like something is in backwards?

[Tony Smith]

Munich Motorcycles when they sold me the kits said they have seen the silver ATE calliper twin disc in models imported to Australia.

There is nothing unusual about the ATE caliper. Many formerly sing disc 79/80 R65s were upgraded to twin ATE calipers via a kit that was available from BMW. The transition year was 80/81 where some twin disc bikes got ATE and others Brembo.

Don't believe anything Munich motors tell you, they would lie about the sun coming up tomorrow if it meant turning a buck.