1982 GS1100G Mastercylinder

[Guest]

I fired up the 1100 and discovered the front brakes were locked up. I let off the pressure and it now rolls. Took off the master cylinder and saw very rusty colored fluid so I decided to flush the system. I was watching 1 of two holes while pumping the front brake lever and noticed a second hole it appeared rusted shut. I decided to drill it out and did until I could see through. The hole I drilled out is the left of the two holes if you were seated on the bike. Now I've found that my brakes will not become pressurized. I plan on JB welding it shut after a thorough cleaning and she the weld is In a putty state so it doesn't drip through. But was wanting to check if there was supposed to be a hole there in the first place.

[Nessism]

Your brake system needs a full teardown.

Remove the pistons from the calipers, clean out the sludge, and install new OEM Suzuki seal parts. Do NOT get K&L brake system parts. They suck.

Replace the brake lines since the old ones are full of sludge too. And flushing does not get all the crap out. Rensport is a popular choice for brake lines. You can make your own from Earl's parts if you are handy with your hands. There is a thread on how to do so.

For the master these work well...http://www.ebay.com/itm/08-2008-KAWA...dYeXjS&vxp=mtr

[bobgroger]

Yes, the second hole is supposed to be there. It lets the pressure bleed back to keep the brakes from staying applied. It is VERY small and I suspect the size is critical. New OEM masters are either not available or cost more than the bike did. Ed is right, do it all front to rear, top to bottom.

[Steve]

By now, you might need a new master cylinder, as that MANDATORY second hole is supposed to be very small. It only needs to be large enough to allow a small amount of fluid to go through at a very slow rate to equalize the pressure in the lines when the calipers heat up. When you apply the brakes, the first thing that happens is that hole gets covered to seal off the lines from the reservoir. The larger the hole, the greater the chance that you have compromised the diaphragm that pressurizes the system. Even worse, drilling out the hole likely left some ragged edges, somewhat guaranteeing the diaphragm is torn.

You will need a new master cylinder with a properly-sized clean hole, as well as a new rebuild kit.

.

[NinjaFlying]

When you say diaphragm are you referring to the piece that is pressed on by brake lever perpendicular to the angle of this hole. Also how small does the hole need to be needle sized?

[cowboyup3371]

Less than that - a single strand from an 18 or 20 gauge wire will slide through just right.

[850 Combat]

I recently bought a new OEM master cylinder for a 1000G. It was over $100, but I didn't think that it was outrageous. I also bought a couple cheap generic ones from China Inc. on E Bay, but didn't have the heart to use one. I have had OK luck with K & L in calipers, but Nessism is right. OEM is a better deal, and you can buy just what you need, mainly the big O Rings in the caliper. Even pistons aren't that expensive on line. Most of the Suzuki calipers I have had apart could have been reassembled without any new parts I think. The fluid crystallizes between the piston and the seal, forcing the seal to seize to the caliper bore. Once you clean everything, including the seals, mine looked OK. I still never re-used them, but I hear that people do. I've used air to shoot the piston into a milk crate of rags. A grease gun would be safer, but I've never done it that way.

Oh wow. I see that at Bike Bandit, a new master is $250. If you went with China Inc. like I have, you would need to switch to a pressure actuated brake light switch, which isn't a big deal.

[NinjaFlying]

I understand the process of how it works now, however previous to the brakes locking recently. I rode the bike 1000 miles at least and I'm going to assume the hole was plugged then. If I were to plug the tiny return hole completely what would the effect be?

[bobgroger]

I understand the process of how it works now, however previous to the brakes locking recently. I rode the bike 1000 miles at least and I'm going to assume the hole was plugged then. If I were to plug the tiny return hole completely what would the effect be?

Just what you saw. Pressure build up and the brakes lock up, after smoking for a few miles. Voice of experience, I still carry an 8mm wrench to crack a bleeder just in case.