How much play is normal for front brake pull?

[clouseau]

I had some down time with the California rain, so I decided to rebuild the front brembo calipers on the 82LS.
There was a significant amount of sludge behind each piston, even though I had bled the brakes not more than 4 months ago when I upgraded to stainless steel lines.
Now that it's all back together and bled (correctly as far as I can tell) there is more movement when I squeeze the handle.
Before, I would only squeeze about 3/4 of an inch and it would be difficult to squeeze it any farther.
The brakes don't feel mushy and it stops OK (I have new pads that need to break in) but I am not used to so much movement in the handle.
Is this normal?

[Bob_Roller]

Possibly , you've still got a bit of air in the brake system .

A little trick to try, is to pull the brake lever in, get a stout rubber band around the handlebar, and brake lever, so the brakes are applied, leave it for a few days .

Every once in a while, tap on the calipers and lines with a piece of wood, as much as you can easily get to, to possibly get any remaining air out of the lines .

Then see if your lever is back to where it was

[drewboid]

Only a guess - now that you have cleaned out the crud behind the pistons they are moving back further than they did originally. This returns more fluid to the master cyclinder. the pistons now have to move further to contact the disk which requires more movement of the lever.
If you made no changes to the master cylinder and the brakes are properly bled this would account for the need of pumping more fluid.

Can you squeeze hard enough to get the lever to contact the grip? If not then you should be OK.  

[Semper Gumby]

Do you have OEM brake lines or stainless?

[Bob_Roller]

He just installed stainless lines 4 months ago .

[clouseau]

Thanks for the replies.
No, the handle doesn't come even close to touching the grip and it's not spongy.
I'm going to ride it more and do another bleed in a few days. I think I may do the rubber band/tap route as well.

[Lucky_Lou]

Only a guess - now that you have cleaned out the crud behind the pistons they are moving back further than they did originally. This returns more fluid to the master cylinder. the pistons now have to move further to contact the disk which requires more movement of the lever.
If you made no changes to the master cylinder and the brakes are properly bled this would account for the need of pumping more fluid.

Can you squeeze hard enough to get the lever to contact the grip? If not then you should be OK.  

+1 with this have you replaced the seals on the pistons when i did mine it took about 100 miles before the brake lever travel felt "normal" i think new seals tend to pull the piston back off the pad a bit if there not "spongy" then i dont think theres an issue with air.
Lou

[bruce_launceston]

I posted last year about a similar concern and I never resolved the cause or fixed the problem.
My lever comes too far back and once during emergency braking I did get it to touch the grip which gave me a scare.

This only occurred after I rebuilt the master cylinder and installed 2 new rotors and braided s.s. lines and new brake pads on my bike. My calipers have never been rebuilt, they are still running original rubbers. (The bike had been sitting for a few years prior to restoration.)

There is no sponginess like you would expect if there was any air in the lines and pumping the brakes makes only a little difference.
The weird thing I have noticed about 3 times is that after the bike was parked out in the very hot sun the lever had much less travel and felt normal.

Possible causes discussed previously were; warped disc rotors - would push the pads back further causing more play.
There was some discussion that the tiny fluid return port in the base of the master cylinder might be partially blocked - I have not had my m/c apart again to investigate this but I believe it could be the cause.

Please let me know if you discover what is causing the problem on your bike.

Cheers Bruce

[Red_Hen]

Sounds to me like you've got air in the lines as Bob said.  I have speed bleeders on my K75 and plan to put them on my R65 as well.  If you go to the www.spieglerusa.com website there is a pretty extensive discussion how they work - essentially there is a check valved so when you're bleeding your brakes, "top down", pouring fluid down the reservoir on the front brake m/c when you release the lever the valve has a spring loaded valve that closes off the system to prevent any air getting back into the lines.  Pretty inexpensive and a good way to bleed.
Also, make sure you've got the right DOT grade fluid in your lines and that it is a good brand - the folks at Spiegler only recommend Castrol, for what it's worth.  Good Luck.

[bruce_launceston]

Thanks Ken (and Bob)
I must get some of those, I had to buy a vacuum bleeder to get them bled from dry after installing the new s.s. lines but it's hard to seal around the thread of the caliper bleed screws. It must be worse on the LS models, I think that air gets caught in the short line between the m/c and the splitter to the twin disks.
I will also try the rubber band on the brake lever again, I have done it before but only to pull the lever in, after reading Bob's post I will use a strap to pull the lever in hard and leave it longer and see if it has any effect.

Cheers

[darrylri]

I have the same situation as Bruce on my '81 R65 with dual ATE disks.  I noticed that the brake lever came very far back before the brakes come on when the PO and I were loading the bike into my truck.  I asked him about it and he seemed surprised; he thought it was normal.  

But the lever travels back to within an inch of the bar before the brakes do something; at that point they work correctly and do stop the bike smartly.  

I'm not happy with this situation because I normally do two-finger braking, but can't because the two fingers left on the throttle prevent the lever from travelling far enough.  

Does anyone know what the right MC piston bore is for a dual disk bike?

[Bob_Roller]

15 mm is the original master cylinder diameter for a dual disc bike, it's cast into the bottom of the master cylinder .

[darrylri]

Thanks, Bob.  I guess I have to look for another excuse, then. Mine's the correct 15mm diameter.  

As the fluid was dark when I changed it last week, maybe there's some built up grunge in the reservoir.