Topic: yet another master cylinder question

[MrGrey]

I've read through many of the brake bleeding instructions on the site but wanted to ask the question before I plopped $50 down on a rebuild kit.

(Preface - first bike noob)

I picked up a 78 550k Saturday that had been ridden almost daily the year before. The front brake was gone - no resistance in the handle. I opened the MC reservoir and it was empty so I figured I'd just fill it and bleed the brake like I would a car. Pumping the handle built no pressure, but I figured it was just because of all the air in the line. I pumped and bled 5-6 times but it never built pressure in the handle. Pulling the handle does push fluid out of the open bleeder. Then I noticed a slight "squish squish" sound when pulling the brake handle in. Figuring it probably needed a rebuild I took the whole MC off. While it was off I put my thumb over the outlet and pulled the handle. When I pull my thumb away I get a "puff" of air.

Am I just being to impatient in my bleeding, or does the "squish squish" sound lend itself to a rebuild?

I have not done the bench bleed by putting the brake line back into the MC (just read that one today), but wanted to get some thoughts on it.

[richvageologist]

Although you have already taken the MC off, this might help. 

Try moving the bars so that the master cylinder is the highest point of the system.  To do this I put the bike on the side stand and turn the bars to the left. 

Normally when I do this, there are plenty of bubbles that come out of the master cylinder into the reservoir.  After these bubbles are gone, I usually start to feel the "pressure" at the lever and can bleed normally.

Hope this helps...

[flybox1]

at any point in the fluid hoses where there is a coupling, banjo, transition from hose to hard line at the caliper, etc., there is an opportunity for bubbles to catch and give squishy brakes.
if your MC is back on, put your bike on the side stand and turn the bars to the left as richvageologist said, and tap on each of these couplings with the handle of a screwdriver.  this will help to dislodge tiny bubbles. 
SLOWLY pump your brake handle to get thes to come up thru the holes in your MC.
let it sit overnight, and repeat in the am.

[Gunner_CAF]

Not long ago I filled the front brakes in our 73 CB500.  The system was completely dry.  It took a while to work the fluid in, maybe 20 minutes.  I filled the reservoir, slowly squeezed the lever all the way, then opened and closed the bleeder before releasing the lever.  I kept doing this and saw little air bubbles coming up in the fluid.  After a while the fluid level finaly started going down and I refilled the reservoir.  When I could start feeling resistance in the lever, I could then pump it several times until firm, then opened and closed the bleeder.  It didn't take long after that to bleed the remaining air out of the system.

Gunner

[Kevin400F]

If you're hearing "squish-squish", you may be getting fluid coming out of the master cylinder around the plunger, lever and associated rubber boot.  If this is the case, you might as well pull the master cylinder, clean it out thoroughly and install a rebuild kit.  Dot 3 brake fluid eats paint, so a leaking master cylinder has other nasty side effects.

[gravano]

You're probably doing everything right; it just takes a while if a lot of air gets in.
Make sure the reservoir always has fluid as you're pumpin away.

[MrGrey]

I still can't get it to build pressure.

I've searched high and low and the only rebuild kit I can find is the dealer kit for $50. Anybody know where I can order an aftermarket kit?

[phrige]

You'll need ring pulling pliers, and
http://www.crc2onlinecatalog.com/master_cylinder_rebuild_kits.htm

You'll need the Honda Parts number, It should be FB-1101 or FB-1102 I think if its similar to the '75 CB550. I havn't bought from these guys yet but I will in the next week or so. The below video was also very enlightening.

Good Luck!

BTW I dig your Avatar, (Big cowboy bebop fan!)

[MrGrey]

Thanks for the link. With shipping their price comes in around what I'd pay at a local dealer.

I tore down the MC last night after stopping by Harbor Freight to pickup some snapring pliers ($3.99 for a set). I have the same set that the guy in the video has, but was able to get them to work by spinning the snapring around so the holes are near the slot for the handle.

[phrige]

Nice, Good to know. Rather than spending $20 for a set of pliers someone recomended online. Ones with a longer reach. I'll have to pay harbor frieght a visit.


Too bad, I was hoping to save you a few bucks with that link. 

[MrGrey]

Picked up my dealer rebuild kit and looked through everything (old and new parts) and noticed I'm missing the check valve. Is it even possible for the MC to build pressure without it? I put the new parts in and attempted to bleed it - but I think I'm just spinning my wheels...

[MrGrey]

It's amazing what can happen when you read.... I went back and read every MC thread I could find to see what I was missing. Making sure the return hole is clear kept sticking out so I grabbed a short piece of a "b" string from one of my guitars and five minutes later the return hole was clear. After about 6 squeezes the brake handle firmed up and 10 minutes later it was bled.