HELP. USED VACUM METHOD HELD 25 INCHES COULD NOT DRAIN MASTER CYCLINDER

TRIED PUMPING FROM THE BOTTOM UP..NO RESULT. ANY SUGGESTIONS

Adjust, repair or unplug the master cylinder so it lets fluid up into the reservoir when the pads are pushed apart, no flow back means you have a problem.

It could be also that you need to adjust the screw on the lever that presses on the master cylinder piston. If the piston is not in the correct position, when pressed or opened, it effectively blocks fluid flow and won’t drain and it won’t allow fluid to flow from the bottom up either. Screw it out a turn and try again. Turn the screw, little by little, until you can pump fluid.

Another possibility is that one of the ports inside the cylinder could be blocked by debris. Use a very fine sewing needle to clear it out.

Edited July 14, 20251 yr by RonH

On 7/6/2025 at 4:44 PM, lemur said:

Adjust, repair or unplug the master cylinder so it lets fluid up into the reservoir when the pads are pushed apart, no flow back means you have a problem.

THANKS FOR RESPONDING, ILL GIVE IT A SHOT

CANNOT FIND ANYBODY IN B'HAM THAT WILL LOOK AT A 2001

On 7/7/2025 at 4:25 PM, RonH said:

It could be also that you need to adjust the screw on the lever that presses on the master cylinder piston. If the piston is not in the correct position, when pressed or opened, it effectively blocks fluid flow and won’t drain and it won’t allow fluid to flow from the bottom up either. Screw it out a turn and try again. Turn the screw, little by little, until you can pump fluid.

THANKS FOR RESPONDING, IT IS HARD TO BLEED W/MY HARBOR FT PUMP WHICH MAKES SENSE IF THE PLUNGER IS NOT ADJUSED RITE

Let"s back up a little bit. Did you have the clutch apart?

I posted how to push fluid back up into a brake reservoir, but the clutch hydraulics are virtually identical with the clutch piston being synonymous to the pistons on the brakes, it's all just simple hydraulics with the biggest difference being it uses DOT fluid or it uses Mineral Oil.  There are very few high spots in a clutch hydraulic system where air can be trapped, so bleeding a trials bike clutch is Not generally a significantly difficult task unless you encounter a mechanical problem such as deteriorated rubber bits at either end of the system.  

Add: parts diagrams show your clutch master to be an AJP model that uses DOT fluid and not Mineral Oil, for a shop to not want to service an AJP clutch they must be a little bit clueless or simply don't want your business, the same parts were commonly used on additional bike makes and models.  The Slave cylinder and piston is unique for your bike but the 2 o-rings inside it are nothing special, the rubber o-rings simply need to be compatible with the hydraulic fluids you are using and you can source appropriate o-rings from anywhere that sells o-rings and or hydraulic service supplies.

 

Hi, I want to share my experience, it may be of value as our bikes are from the same era.

I have a 1998 GG TX270, when bleeding the front brake I found that the passage hole from reservoir to piston of the brake master cyl. was not drilled all the way through at the factory.

As the brake pads wore the lever kept moving closer to the handle bar and eventually not applying enough force on the pads to be effective. I assumed air got in the line.

In actuality there was no new fluid coming down from the reservoir to take up the fluid volume of the caliper piston pushout. I disassembled the master cyl. and tried to push a needle through the passage assuming it was just plugged.
With careful inspection looking in the cylinder I could tell there was no passage hole breaking through. 
I carefully drilled and deburred a small hole finishing the hole from the factory. 
perhaps this could be the issue with your clutch master cyl.
Of course, I had to do this the night before a trials event. It's always that way. 
Good luck with yours.

Trailercamp the issue you are describing is you had the lever adjustment too far in which stops the piston from traveling its full range. You fixed a 27 yr old problem?

On 8/8/2025 at 2:07 PM, trailercamp said:

Hi, I want to share my experience, it may be of value as our bikes are from the same era.

I have a 1998 GG TX270, when bleeding the front brake I found that the passage hole from reservoir to piston of the brake master cyl. was not drilled all the way through at the factory.

As the brake pads wore the lever kept moving closer to the handle bar and eventually not applying enough force on the pads to be effective. I assumed air got in the line.

In actuality there was no new fluid coming down from the reservoir to take up the fluid volume of the caliper piston pushout. I disassembled the master cyl. and tried to push a needle through the passage assuming it was just plugged.
With careful inspection looking in the cylinder I could tell there was no passage hole breaking through. 
I carefully drilled and deburred a small hole finishing the hole from the factory. 
perhaps this could be the issue with your clutch master cyl.
Of course, I had to do this the night before a trials event. It's always that way. 
Good luck with yours.

 

So did you fix the clutch? Posting about a front brake is not the same. LOL.

I talked to Dirt Riders and told him BS i got from seller(you have to let the clutch warm up before it will disengage) He had heard it before and told me

1. crankcase had been contaminated or mixed disk was not installed or installed wrong. Waiting on a clutch now

In case they have not told you, the pressure plate only goes on one way. On the clutch one of the posts will have a notch in the end of it. That aligns with a mark on the pressure plate. Good luck.