Beta Riders Club Discussion Forum

bit of a long shot, but the front brake is starting to get a bit grabby on the RR300, my dealer suggested it's probably just the seal in the master cylinder as the bike is only 10 months old, and said i could try just replacing that instead of getting the complete rebuild kit.

anybody done this, and do you know the seal size? i'm thinking of just getting the dealer to do it as part of its service but my circlip pliers aren't long enough to pull things apart and measure it myself. thanks in advance...

That sounds like an odd diagnosis to me. I never had a Nissan brake do that and I've had one on every bike I've owned since '00. If the piston seal was bad it would leak internally or externally and likely draw air and feel spongy not grabby. When you pull the lever slowly and firmly, does it feel "jerky", like it's grabbing and letting go ? If so it's simply the lever pin / piston that needs a cleaning and a dab of good grease.

Glenn is probably right. Dirt and grit get in the pivots and can wreak havoc. When servicing your bike it's a good idea to put a drop of oil on any pivot point. I even do the toe piece on the shifter. If it doesn't feel nice and smooth after oiling it needs to be cleaned then re oiled. It's amazing how much better a bike feels when all the levers and other moving parts work nice and smooth.

My brake was grabby when it was new. Probably just because the Brembos have a very good feel and not quite as much power per pound of pull. After a year I'm getting very used to it and the grabbiness is gone.

thanks for the fast replies guys... yep glenn, it's getting grabby so instead of a smooth progression the brake applies in about three to four abrupt stages so is quite jerky so it will probably be the piston as you say.

first thought was the pivot point but greased that so then knew it was internal. it was the beta dealer's suggestion it would probably just be the o ring but i'll try cleaning and greasing the piston first.

The steel pad in the end of the rubber boot that the lever pin contacts and rides on. There is considerable force on this small area as the lever moves and angle changes, and when its dry the feel dramatically changes. Just break down the entire system (not internally) and clean/lube everything. The caliper as well, the guide pins are not maintanence free. I service my controls regularly because they always get fouled with mud and sand. I have never, ever had a Nissan master cyl apart for a problem. My brother bought a used 300RR that saw basically zero maintanence. Brake did the same thing, he thought the worst, fixed in seconds. Basic stuff first.

all good, as you said glenn the piston just wanted a bit of grease and the lever action is back to normal. good to know as i would have been a bit surprised to need a rebuild kit, or just the rubber o-ring, at 1000km.

i will try these suggestions this arvo , my front brake has been extremely grabby and there is no adjustment . only adjustment is the lever position i.e further out or further in . i normally drag my front brake slightly to keep it planted in a rut and the suspension pushing into it . last few weeks just slightly touching it is making me wash out , i had at least 4 wash outs downhill into a corner and into a few berms yesterday .

betajuice wrote:all good, as you said glenn the piston just wanted a bit of grease and the lever action is back to normal. good to know as i would have been a bit surprised to need a rebuild kit, or just the rubber o-ring, at 1000km.

when you say piston , do you mean the piston in the lever housing that the pin connects to / pushes against , or the piston in the caliper pushing the pads to the disc ?

The external piston in the master, small steel pad at end of rubber boot that the pin in the lever pushes against.