General Brake Question

mikromo · Jan 17, 2003

Sorry, this realy doesn't pertain to dirtbikes, but maybe someone can help. I'm currently reassembling an old Kawasaki triple, that has been in my garage,for at least 5 years, and in a freinds garage at least 5 years before that. I'm working my way from the front to the back, and I'm to the bleeding of the front disc brake part. I had to disassemble the entire system for cleaning, and replaced one of the brake lines. I reassembled the entire system dry(no fluids) and now I'm having a devil of a time getting it bled. Should I remove the Master cylinder and push brake fluid thru all the lines and into the caliper to "prime" the system? I've left the bleed screw open now for 2 days and still no luck( I was hoping gravity would work ) I've hooked up my vacumn pump and cant get it to draw the fluid down to the caliper.The system is air tight with no leaks. Any freindly advice? I've never had this problem b-4 on any of my dirtbikes, but I've never started with a "dry" system either. Any suggestions would be greatly appreciated.

bscottr · Jan 17, 2003

Have you tried "pumping" the brake lever while your vacumn is attached? If it doesn't work then you may open up the master cylinder to look for gummage.

JWW · Jan 17, 2003

I would try and force it through from the caliper. If you cant get it through you might have something blocking the flow.

bclapham · Jan 17, 2003

maybe try go from the bottom up? Get a large syringe or squeezy bottle, connect a tube to the caliper bleed andput the fluid in from the bottom. be careful, if you press to hard, the tube might come off and you will get a face full of fluid!

mikromo · Jan 18, 2003

OK, Hope someone out there can shed some light. last night I reverse bled the front brake, and if I cracked open the master cylinder/brake line connection, I got fluid all the way, but with the system sealed fluid would'nt fow into the master cyl.. I dissasembled the master cylinder and this is what I found. By the way this is a master cyl. off an older honda, not original, but nearly identical to original. if you pump it no fluid will shoot out. in the bottom of the resevor there is a hole leading to the actual pumping area, but it appears that no mater what the lever position, it leads to behind the primary cup(seal). several mm's foward of that is the beginnings of another hole, which was never drilled through, and I suspect that there were several applications of this piece which determined which orfice was opened up at the factory. This is my therory: I used a rebuild kit for a generic old honda. Might it be designed for the unused orfice? If I pull the piston back far enough to let fluid into the chamber, it shoots out like a new one, but once the piston is operated from its normal assembled position it soon runs out of fluid and stops pumping, I think because its unable to replenish from the pre-drilled orfice. It appears that the 2nd, unfinished orfice is in the proper location to replenish the cylinder. Any opionions on whether I should try drilling out the 2nd orfice and trying that? If so, should I epoxy close the original hole or just leave it open? This, as you can imajine is very frusterating, so any help will be greatly appreciated

tx246 · Jan 20, 2003

every street bike master cylinder that ive peered into has two holes. one is fairly large and the other one is itty bitty. if the itty bitty is clogged the thing wont work. bike master cylinders generate a fair amount of pressure but have a very small fluid volume movement when actuated. just like a car, you need to bleed the master cylinder before hooking up to the brake line. you should be able to hold your thumb over the brake line hole and get pressure when you move the lever. if not cover the hole with your thumb and pull in the lever. take your thumb off the hole briefly, then cover it back up before letting off the lever slowly. this should suck fluid into the right places. repeat until you get a good shot of fluid/pressure.

if you have been wailing away at the brakes for awhile you probably have lots of air in the lines. the master cylinder wont displace enough fluid to move the air out the end of the line. another trick is to make sure the wheel cylinder piston is compressed in the caliper as far as it will go, then use a c-clamp to keep it in place until you get real brake pressure. this helps keep the brake fluid volume smaller.

another hint is to tap on the master cylinder with the end of a screw driver and look for small bubbles while you pump. its amazing at how small a bubble will keep the thing from working. i too like filling the system from the caliper with a hypo purchased at the feed store.

i feel your pain i worked on a friends honda magna for 3 nights before i got it to pressure up.

General Brake Question

mikromo

bscottr

JWW

bclapham

mikromo

tx246

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