Topic: simple question: brake lever free play

[Raul CB750K1]

I just noticed yesterday that my CB750 brake lever have some free play (about half an inch) from the point where it is extended the most, to the point where it starts to actuate the brake pump. Is that normal? I don't recall having noticed that before, and my modern bike is not like that.

Thanks in advance

Raul

[cntrhub]

I'd pretty much say the levers back then were somewhat sloppy. A half inch or less seems about right.
As long as the front brakes don't drag, then most likely the plunger has returned. If the plunger hangs up, then there is where you will have a lot of lever movement. The pivot as well as the tag end touching the plunger can be worn down a little. This can add to the excessive movement of the lever

[Jonesy]

Looking at the parts books, I think the later 750 MC had an adjustment to cut down on the slop. I *think* the K1 was before this improvement.

[Uncle Ernie]

Is it a matter of bleeding the brakes? Does the bike stop before the lever hits the handlebar grip?

[Raul CB750K1]

The bike stops just fine -well, kind of, as good as that old bike brakes are-. The lever never touches the grip. That is, from the fully extended position, there is some part that the lever just "wiggles around" because it is not touching the plunger. Then, it starts to brake as normal without going too far. My question is wether that free play is normal. There is nothing wrong with the lever, so maybe it is just a problem with the brake pump. I don't think so, because I personally rebuilt the master cylinder and all the new parts were exactly the same than the original. I will post a picture whe I have a chance.


Raul

[Terry in Australia]

Raul, if your lever is not contacting the piston then the piston is either stuck, or the lever (or piston) is incorrect for your M/C. If all is well, there should be virtually no "slop", the "cam" on the lever should be in contact with the piston, and the brake should be coming on as soon as you start to pull the lever in. If your lever even comes close to touching your throttle grip, your brakes need bleeding, or your hoses need replacing, or both.

Interestingly early test reports raved about how you could squeal the front tire from 100 Mph with the OEM brakes, all I can say then is that tire technology has improved about a million percent since then, the only thing squealing if I have to make a panic stop from that speed is my mouth, and I won't mention the noises that are coming out of my other end, ha ha! Cheers, Terry.

[dusterdude]

my lever vibrates and shakes like a hula dancer,but i have good leverage with it and stop just fine.

[Raul CB750K1]

I took some pictures today. How does your brake lever look like? There is a picture where the lever is fully extended, and the cam doesn't touch the plunger. The other one is when the cam just barely touches the plunger. It is just a few millimeters, but on the other end of the lever it is about half an inch. As I said, I rebuilt the master cylinder and the plunger was exactly the same that was fitted, and the lever is the one the bike came with, and I think it's standard. I will check the parts manual, maybe there is a way to adjust it at installation time.


Raul

[Gordon]

Mine has always done the same thing, Raul, even after rebuilding the MC and bleeding.  It's one of those things I attribute to age, and as long as it doesn't affect the performance of the brakes, it doesn't bother me.  The bike stops fine and the lever doesn't even get close to touching the throttle grip. 

[Raul CB750K1]

Thanks Gordon, that's exactly what I wanted to know, wether it was something odd or just the normal thing. I guess, as it was the very first street bike with hydraulic disc brake, that the design was not completely optimized by the release date...


Raul

[Jonesy]

Looking at the parts books, I think the later 750 MC had an adjustment to cut down on the slop. I *think* the K1 was before this improvement.

OK, I stand corrected. (I guess I don't have a photographic memory... ) I looked in the parts book and they started with an adjuster, but according to the book it was dropped after the original K0 model. So, I'd concur the condition Raul described is normal, since my bike does it and it sounds like many others do too.

[Raul CB750K1]

Great!!! In that case I can sell my brake lever as "sandcast"     Knowing it is normal, it is now more a peculiarity than an annoyance...


Raul