im about to buy a 1995 cbr600 f3 and when i rode it i noticed this same problem that happened when i rode my cousins cbr600 f2. and i've looked on the forum a bit and i haven't seen anyone else have this problem. :/

so when your starting to slow down and you're gradually and constantly pulling in the front brake it seems like at one point all of a sudden the brakes grab. it's hard to explain so bear with me.

it started happening on my cousins bike after he laid it down and i've noticed that this one im about to buy also has been laid down on he right side and actually the lever is broken now a bit.

it seems like the mc isn't moving till there's alot of pressure. then suddenly it breaks free and then the brakes are applied quite a bit.

any help or ideas would be appreciated!
thanks!

 

That's more common that you think. Mostly it's due to old brake fluid. Most riders don't give it any thought. If you look at the master cylinder window and it has a shade of brown, it needs replacing. Taking the master cylinder apart is easy to do. You can buy a rebuild kit for it for less than $40. Cleaning and rebuilding the brake calipers would also be a good idea. New caliper piston seals too. Doing these things will have your brakes working like brand new.

 

Could be few things from the pads being glazed, not properly bedded in, uneven wear pattern on the discs even to loose or worn head bearings believe it or not.

Just a few things to check to get started.

 

All of the above. Make sure brake fluid is changed, check pads themselves for cracked or glazed, and make sure your piston isnt sticking.

 

okay so i looked at it a little bit more closely today and well i know it's not the a worn spot in the disk or pads because i know what that feels like. i do know the head tube bearings do need replacing and i noticed the when pulling the lever in the plunger was actually a little rough. not as smooth as i said about. (it's hard to tell while riding) is goes in kinda like forks when they are really old and need fluid.
but to fix this would i need to rebuild the mc? or buy a whole new one?
thanks!

 

Does the lever move freely? Sounds too simple but I had a problem like that only because the brake lever was a little sticky. If pulled exactly straight it moved smoothly, but while riding I grab the lever at a slightly different angle and it came on jerkily. Some white silicone grease sprayed into the pivot on the brake lever fixed that on my bike.

The first day I got my 600F3 I wanted to see how it felt to brake very hard, I pulled smoothly and a sudden jerk momentarily locked the front brake and maybe did a small stoppie at the same time. Scary!

 

Sounds like the perfect time to upgrade to a radial master cylinder, the 04 and newer R1 masters are awesome. Another thing I would do is buy a rebuild kit for the calipers, and maybe some new lines.

 

the lever i knows moves freely. it's only when it's trying to push the plunger in that it starts like kinda sticking. would any kinda of grease spraying like in the plunger area work some how? or would it destroy some grommet or something.

and would an 04 R1 mc just bolt right in basically?

 

Yeah, most m/c's are universal, as far as the grease goes, I've never seen any.