1976 GT 550a Asco Master Cylinder

[carvan4040]

HI

I have just bought a rebuild kit for the above Asco master cylinder. Not having a diagram of what order the parts go back (the parts i took out were possibly in wrong to start with so can't use that as a guide) can anyone help out. The bits that have me stumped is the flat copper washer and which way the spring goes back as one end is tapered.

Any help appreciated

Richard

[carvan4040]

Come on guys surely somebody can help me. I think i have it right but can't get the master cylinder to bleed.

[Flywheel]

http://www.oldjapanesebikes.com/mraxl_G ... index.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Look under Shop Manuals then Suzuki Disc Brake Manual. Hope this is of some use to you.

[carvan4040]

That's no good i have a number of different shop manuals and the diagrams aren't detailed enough and they only show the Tokico master cylinder .

[yeadon_m]

I find the exploded diagrams on alpha sports-Suzuki very good (google) and I know they show both Nissin and Asco m/cyls

[Suzsmokeyallan]

Why not post up a photo of the parts you have in the kit and we should be able to get them in the correct order for you.

[carvan4040]

Thanks for that here's the photo

[H2RICK]

If that blunt (working) end of the piston DOESN'T have a little 6 bladed flower rivetted to the face of it then the separate check valve is missing. It's a little black metal piece that is dish-shaped and is trapped by the spring.
The spring itself SHOULD sit with the large diameter end to the outlet hole where the banjo bolt threads in.
The small black rubber cup in your pic SHOULD sit on the blunt end of the piston with the cup facing the outlet hole. The spring should sit with the large diameter end at the outlet hole with the separate check valve fitted into that end of the spring. The small diameter end of the spring should fit into the cup and hold it in place against the blunt end of the piston.
I'm concerned that your picture doesn't show the check valve in the parts.....although that may NOT be a part of the kit. Sometimes the kit people expect you to reuse your old check valve.

If you are having problems getting the m/c to hold pressure (and assuming the parts are installed correctly as per the above description), then I would recommend bench bleeding the m/c BEFORE you hook it up to the rest of the system. This process works best if you clamp the m/c into a vise as the m/c would sit on the bike. Use your thumb on the outlet of the m/c to take the place of a bleeder screw and get rid of all the air in the m/c FIRST, bleeding it like you would bleed a caliper. It's a messy job so wear safety glasses and keep plenty of clean rags/towels to hand.....and don't forget to keep the fluid in the reservoir topped up.
Once the m/c is bled and holding pressure against your thumb, you can now hook the m/c up to your system and start gently pumping fluid through to the caliper, using the caliper bleeder screw in the normal way. If your system has been completely drained it can take a lonnnngggg time (relatively speaking) to get all the air out of the system. Patience is the key word here.
Good luck and let us know how this turns out.

BTW, this is very interesting as I've never seen the Asco stuff used on anything but the 1977 bikes......even though Alpha Sports shows Asco stuff as being used for a number of years. Live and learn, I guess.....

[carvan4040]

Thanks for the reply. I believe that the asco MC does not have the check valve in it , when you look at diifferent pictures of the kit on various web sites it does not show it. I know when i pulled the mc apart there was no check valve. That metal flower thing you described is only on the Tokico MC's . My question is does the flat copper like disc that comes with the asco kit go between the blunt end of the piston and the black rubber cup (I think it's the primary seal)?

[Suzsmokeyallan]

You are correct, the little disc sits on the blunt end of the piston and the flat side of the rubber sits against it.
Order of assembly is lube the bore then put the rubbers concave side nipple onto the springs small end hole clip and drop it in the cylinder, spring side first. Apply a little brake fluid to the disc and rest it centred on the flat portion of the rubber, then carefully push the parts in the bore with the piston.
Do the rain dance for getting the circlip in, what I do to make it easy is to apply a bolt into the threads and stick the cylinder into a vise held by the bolt so the cylinder is vertical. While pushing down on the piston get the circlip in level near the top then use a piece of small copper pipe or similar to push it down into the groove.
Once its "clicked in" then apply the boot as necessary, a bit of waterproof grease in the boot doesn't hurt either.
For bleeding you can use Ricks method although I prefer a Mityvac or similar and simply draw the fluid down the system once its been completely assembled.

[H2RICK]

Well, gents, my Asco "consciousness" has been raised again.
I'm amazed that they use a copper disk as a check valve.
Weird.
Another reason to stick with Tokico and Nissin, I'd say.

[carvan4040]

Thanks for the replies it was a great help and confirmed how i thought the parts should go. Got the mc to bleed i had a blocked bleeder hole, you can't see the hole unless you take the actual reervoir off. Normally you wouldn't need to take it off but i had to replace a leaky O ring . M/C now workds great.

Cheers everybody.

Richard

[Beefy666]

I have the same kit how did you do yours tried all ways

Thanks
Beefy