Brake Flushing With Pressure

I want to flush my KZ brake system as folows:
- Using pressure bleeder, blow out all fluid.
- Disassemble master cylinder and calipers.
- Clean out sludge, rust, dirt, ect.
- Re-assemble, grease all sliding points, fill with new fluid & bleed with pressure bleeder.

I've done this sucessfully on cars before. The pressure bleeder really makes the bleeding easy. But I'm having a problem on the KZ. After pressurizing the system and opening a bleed screw, the fluid doesn't blow out as I would expect. A little flows, but then it stops. I increased the pressure to 15 psi, but no more fluid would come out, and I was concerned that my 29 yr old master cylinder plastic resevoir wasn't up to additional pressure. I can get more to flow out by working the brake lever, but even then it seems that something's not right. Pressing the brake lever, fluid will start to flow, then stop until the force on the lever is increased. After getting the fluid flowing with increased lever pressure, the lever eases up. It seems that there is a restriction in the system. Or possibly some kind of weird check valve operation. Is this normal? Or is it more likely that dirt is plugging some opening? Should a pressure bleeder work on this system? I aborted my disassembly because I wasn't sure I understood the system and because I wasn't sure I was going to be able to bleed the system properly.

Bemoore,
I have a '77 KZ650C1 (original owner) and I use a KD2222 pressure bleeder to do my brakes. I use an adapter that I made from a spare reservoir cap (as I'm sure you know, you must plug the cap venting to keep it from leaking under pressure). I use 15 psi and have not experienced the problem you describe. It sounds like something may be plugged up a bit. Do you have the same problem on both the left and right front brakes? If so, the problem must be above the splitter or with the bleeder. If it's only one side, the problem must be below the splitter. Before you dig any deeper, you may want to try bleeding the rear brake. If you have the same symptoms, it may be a problem with the pressure bleeder rather than the brake system. Good Luck Ed

I had this problem before and it was old brack fluid that turned into a gell/hard crust the fluid was brown almost black. I had to put alittle bit of carb cleaner into the brake system and let it sit for about 5 min and it then flowed freely. I then ran alittle bit of clean fluid through the system and rebled the brakes and everything has been fine since.

Let's try this again. I posted earlier, but I got an error and the post didn't show up.

650ed, My bleeder came with an adapter that works on many master cylinders, including the KZ, so I don't have to plug anything to get the pressure to build. I'll try the other caliper & see if it works any better.

oldkaw79, You are braver than I am. I wouldn't get carb cleaner anywhere near rubber, especially master cylinder seals. Although your experience indicates that if I can get the old fluid replaced with new fluid everything should start working fine.

Thanks for the info.

I decided to consult my Clymer manual to see how to disassemble the calipers, and if there were any gotcha's. The only thing I could find was a section on Caliper Rebuilding, in which they indicated that specialized equipment is needed, and to not attempt. I just want to disassemble the calipers so I can clean them out. Are any specialized tools needed?

Same question goes for the master cylinder. I want to disassemble it and clean it out too.

bemoore wrote:

I decided to consult my Clymer manual to see how to disassemble the calipers, and if there were any gotcha's. The only thing I could find was a section on Caliper Rebuilding, in which they indicated that specialized equipment is needed, and to not attempt. I just want to disassemble the calipers so I can clean them out. Are any specialized tools needed?

Same question goes for the master cylinder. I want to disassemble it and clean it out too.

clymer sheesh...thats why you shoulda got a factory manual...both of these parts come apart easily. use compressed air ( with a rag to catch the caliper piston ) and not lose a finger and the master comes apart even easier depending on what type it is. i did two sets of calipers recently with no problems...just watch for pitting and replace the pistons if you have it...steve

i shoulda added you pull the dust seal off first and then pry the dust seal holder out with a small screw driver...sorry:) steve

Post edited by: fixer5000, at: 2006/06/19 16:12

fixer5000,
Thanks for the info. Are there any tricks to getting the seal back in place?

Next, I need to clean out the master cylinder, but I'm going to start another thread for that. See kzrider.com/component/option,com_joomlab...id,5/id,55596/#55596

when i did mine i used some clear silicone grease on the lips.not a blob just a light coating... it makes them slide right back under that thing metal ring...steve

fixer5000,
Thanks. That sounds like a good tip.

Thanks, everyone for the tips. Last night I got one caliper finished. The hardest part was getting the piston out. 90 PSI wouldn't budge it. I had to put it back on the bike, bleed the system, and use the brake lever to force the piston out using fluid. I found a fair amount of gunk inside. It's all cleaned out now. The biggest surprise to me was the sliders. Before, they were really hard to move. Having zero experience with motorcycle calipers, I thought that some of this may be normal. I cleaned the sliders and the caliper (slider holes) with brake cleaner. I then hit the sliders with a brass brush on my Dremel. The difference was barely noticable. However, after greasing, I couldn't believe how slick thay worked. Now the caliper slides back & forth easier than any automotive caliper I've serviced. I can slide it around easily with one finger. It's now back together and back on the bike. Now I just need to do the other caliper.

Thanks.