The Tiny hole in the MC reservior and a soft brake lever

I just finished bleeding the brakes and still have a soft lever. I read in other posts that the tiny hole in the reservior should be cleaned from gunk and that this may be part of the problem. I just rebuilt my MC and cleaned out the tiny hole and still have a soft lever. When I first pull the lever the tire does not stop, it slows but not stopping, when I spin the tire the second time and pull the lever it stops quickly. I read that the tiny plays a big part in releaving pressure and that if you have the cover of the reservior off a stream of fluid can come shooting out. I have the cover off and watched but it doesn't look like anything is happening through this tiny hole. Can someone please help explain what the tiny hole does and if this could be the problem. I cleaned it with one strand of wire from a wire brush. Was this too small?

 

The "Tiny Hole" keeps the Hydraulic Pressure stabilized.
If you have Fluid gushing-up out of that tiny hole; you have a Master Cylinder that could have a leaking Hydraulic Seal.

As the Brake Pads wear, the Master Cylinder needs a way of keeping the pressure on the Pads instead of losing ground to the Pad wear.
This happens by the Fluid in the reservoir filling the Bore between the two Seals each time the Lever is pulled.

The Primary Seal is seated on a Ram which has several holes drilled into where the Seal seats to allow fluid a one-way passage to the back of the Cylinder.
As Fluid passes by the Primary Seal the "Tiny Hole" allows Fluid from the reservoir to enter the Master Bore behind the Primary Seal and in front of the Secondary Seal.

It's small diameter keeps the System under pressure.
If it were larger; the Secondary Seal would just refill the reservoir with the Fluid in the Bore between Both Seals ... not forcing Fluid through the drilled ports on the Ram behind the Primary Seal.

When the Primary Seal wears-out or the Bore becomes pitted or irregular due to some build-up on the Bore's inside surface ... Fluid is Not pushed down through the system ... instead it remains in the Bore ... where the Secondary Seal will force it back into the Reservoir making the Reservoir look like a "Little mini Old Faithful"

 

thanks Rick. My MC is ok then because I can't see anything happening from the "Tiny Hole" when the lever is pulled. I just can't figure out now why the brakes don't stop immediately on the first pull of the lever but the second time the do.

 

Did You bleed by just pulling the brake lever or did you use a vacuum bleeder? Will make a diff. if you use a vacuum bleeder

 

Get somebody to help you work the Brake Lever.
Pump the Brake Lever several times to build-up hydraulic pressure.
Have the assistant KEEP Pressure on the Lever while you open the Bleed Nipple.
As the Fluid leaves the Caliper ... have the assistant HOLD the Lever firm to the handlebars.
Close the Bleed Screw.

Repeat this process until the System is free from Air Bubbles.

It's a lot easier to do if you have a piece of clear vinyl hose attached to the Bleed Screw and the opposite end of the hose immersed in Brake Fluid in a glass jar.
You'll see the Fluid traveling in the hose.
You see any bubbles leaving the system.
When you have the system free from air bubbles; your Brakes should be good.
If the System won't "Pump-up" ... The Master Cylinder's Seals ain't cutting it!

 

This is the closest thread I can find in relation to my problem so I'm adding to it.
When I removed the cover from my resevoir it looked "Dust in the Wind". I have cleaned it thoroughly inside & out. Totally amazed the "innards" came out with minimal effort. 2 questions.
1) Resevoir has the little hole I cleaned out and next to it more of a "divot" than a hole. Should I have 2 holes and I just haven't cleaned the "divot" out?
2) Does anyone know what the small piece between the C-Ring and the main metal plunger is in an exploded diagram? I don't recall seeing that and I don't think I dropped anything while taking apart the cylinder resevoir.

'82 XJ650J Thanks

 

that "divot" has a tiny hole that has to be cleaned out with a single strand of wire from a wire brush or something similar. otherwise, your brakes will probably drag... no, not probably.. they most definitely will

looking at the diagram, that piece between the plunger and the c-clip is the rubber ring that slips on to the plunger... they just couldn't find a better place for it on the diagram.

 

Excellent! Thanks for the info. I'd say that explains why I'm having the problem I am. Perhaps I need glasses.

 

ACK!!!

I have an "old faithful" effect in my MC,

Will a rebuild kit be needed or is it possible just a good cleaning?

Still have some mushyness in mine, better after the last bleed, but still there, suspecting this is causing it.

 

That's a good sign why you have the mushy lever.

Throwing a Kit in it won't be too much of a pain.
After the fight getting the Criclip out ... you're home free.

 

Finding the kit for a decent price could be the biggest problem....
May actualy be cheaper to simply replace the mc.

A bit more digging tomorrow.

 

I'll assume that you have given Chacal a shout in your quest for a rebuild kit. He might even have a direct or similar replacement M/C.

 

Actually I haven't hit Chacal up yet. Gonna try him now.
I need a spare key sooooo
A quick scan around seems to show it's the same MC as the XJ550 SECA's and some of the XV250's. (after peeking at Old Bike Barn, apparently all of the XV250's (part # change) )
Prices I've seen so far are in the $40+ range.
I can get a new MC for the $40-70 range...
My MC has seen better days physically, so the debate is on fix or replace.