XJ1100 Proportional valve

Hi everyone,
I'm addressing this question to XJ110 owners who have already had to rebuild the rear master cylinder on their motorcycle. I'd like to know if it's necessary to also disassemble and clean the proportional valve.
I know there are no replacement parts for this valve, so I want to avoid damaging anything.
Thank you in advance.

 

If you're pulling the rear master, at least opening and cleaning the proportioning valve should be done. As I recall, it was easiest to pull them both as an assembly instead of fighting the tube nuts in place. A couple pages attached if you don't have them already. Unsure on the availability of parts, but I'd hit up @chacal as he'll either have the answer or the parts. If you find the proportioning valve to be trashed, converting the brake system to a standard system where the rear pedal only runs the rear brake and front master runs both front discs is an option and simplifies your hose arrangement.

Note the warning below "Never disassemble or adjust proportioning valve!!!". Well when your bike is 45 years old and the parts have sediment and corrosion, you're left with your own skills and judgement on how to proceed.

 

Hi Roast644,

You're right. Unless I'm mistaken, or Chacal confirms otherwise, I haven't found any replacement parts for the proportional valve on the XJBikes Marketplace or anywhere else, so I'll avoid opening it to clean it. Since I don't know if there are O-rings or seals inside, I'll also avoid spraying brake cleaner through the openings. I'll simply circulate brake fluid and make sure it flows properly through both ports. If the valve malfunctions, I'll isolate the front and rear brakes by replacing the front master cylinder with one from an XJ750, which is suitable for operating two calipers.
Thanks for the advice.

 

If you decide to crack it open, here's what you'll find. Cap with seal, sealing washer, washer with prongs down on top of the spring, spring and plunger. In the bottom of the valve there is another lip seal.

Seal in the cap appears to be 7.5mm ID x 12.5mm OD. Seal at bottom 8.5mm ID (??) or at least that was the diameter of that portion of the plunger. Maybe 12.5mm OD also, but I didn't yard it out of there to check. Looks like a fun one to extract if a guy was inclined to do so.

There's no adjustment, nothing magical inside. This whole master cylinder unit is fairly clean, and there was still some gunk inside that flushing may or may not remove.

 

I see my photo is blurry as Bigfoot now, but the seal in the cap is a lip seal also.

 

Wow, thanks for the photos. As you said, there's nothing complicated and nothing that can't be replaced. In fact, even the plunger could be machined new. I wouldn't mind taking it apart and cleaning it. Thanks again.

 

Hi Roast644,

This is what the lip seal looks like. It's the most critical part in the assembly of the proportional valve. Handle with care.

 

That is definitely a unique critter. Good job getting it out in one piece.