Brake Pad Knock Back

[Ccitis]

Ok, if using rubber hoses, I would use a 16mm (5/8") or 17mm (11/16") bore, the 14mm will make the lever too spongy.

I don't know what the original is. The lever is very firm... and then you move the bike and it gets soft, but then one more pump firms it up. Thats what is so odd and lead me to think the pads were knocking back. But there is nothing obvious out of round.

[bikerphil]

The original is probably an 11/16".

[cajun31]

Sounds weird for sure. Have you verified that the spooge hole is completely clear? Brakes not releasing? Clogged Spooge hole? - XS11.club Forums I know the maintenance tip reads not releasing but what you are describing about the handle going soft all the way to the grip indicates the fluid is not releasing properly. Sort of like a vacuum problem which leads back to the spooge hole. Just something easily checked. One other thing and it has been mentioned. Have you closely inspected the master cylinder bore for pitting etc, Has it been cleaned or honed to the point of being too far out of spec and the rubber on the plunger is not sealing properly. Have you noticed any brake fluid seepage at all? The brake system on these bikes was never the best to begin with but if properly cleaned they do the job. Sounds like you have been through those brakes a number of times already but if I were sitting in front of that bike I would be completely disassembling everything and making sure everything is cleaned, flushed and spotless. Throwing parts at the problem before being completely sure of what the problem is to begin with can get costly.

[Schming]

Sounds weird for sure. Have you verified that the spooge hole is completely clear? Brakes not releasing? Clogged Spooge hole? - XS11.club Forums I know the maintenance tip reads not releasing but what you are describing about the handle going soft all the way to the grip indicates the fluid is not releasing properly. Sort of like a vacuum problem which leads back to the spooge hole. Just something easily checked. One other thing and it has been mentioned. Have you closely inspected the master cylinder bore for pitting etc, Has it been cleaned or honed to the point of being too far out of spec and the rubber on the plunger is not sealing properly. Have you noticed any brake fluid seepage at all? The brake system on these bikes was never the best to begin with but if properly cleaned they do the job. Sounds like you have been through those brakes a number of times already but if I were sitting in front of that bike I would be completely disassembling everything and making sure everything is cleaned, flushed and spotless. Throwing parts at the problem before being completely sure of what the problem is to begin with can get costly.

To add to this post if I may, if the MC was rebuilt or not, are the piston's seals in the proper position ?

[Ccitis]

Pulled everything apart again, even popped a wheel bearing out to make sure the spacer was in correct. It did have a bit of slop so I reset the bearings. But, same issue with the brake. So, ordered a master cylinder rebuild kit. Can't think of much else.

[Ccitis]

Any one have photos or diagram of how the master cylinder should be assembled? I will make sure the new parts are in there correctly. The service manual is not super specific.

[cajun31]

Just pay attention to everything as you disassemble and make sure everything new goes back in place. There are several tech tips in the maintenance repair section. Master Cylinder Rebuilding - XS11.club Forums Master Cylinder Rebuild - Plunger rubber installation - XS11.club Forums. There is a large rubber o ring that seats the master reservoir to the base. You have to pry that off to get good clearance to the spooge hole. I use a small piece of wire to run it through the hole to clean it. You will be able to see the wire come through down the plunger bore. There are better tools then wire to clean it but the wire works and you usually have that laying around not having to buy a special tool for the job.

[Ccitis]

Just pay attention to everything as you disassemble and make sure everything new goes back in place. There are several tech tips in the maintenance repair section. Master Cylinder Rebuilding - XS11.club Forums Master Cylinder Rebuild - Plunger rubber installation - XS11.club Forums. There is a large rubber o ring that seats the master reservoir to the base. You have to pry that off to get good clearance to the spooge hole. I use a small piece of wire to run it through the hole to clean it. You will be able to see the wire come through down the plunger bore. There are better tools then wire to clean it but the wire works and you usually have that laying around not having to buy a special tool for the job.

I have just been in there cleaning it up again. I have been in there many times. The "spooge" hole is clean as they come. I was more asking because perhaps i installed the components back in wrong. Those also show a different master cylinder. Mine is a 80 G model. I assume the innards are similiar.

[cajun31]

You can zoom in on this and it will give you some idea as to what order things go in. Yamaha Motorcycle 1980 OEM Parts Diagram for FRONT MASTER CYLINDER | partzilla.com

[bikerphil]

I'll see if I can take one apart and take a pic of it.

Front master cylinder M/C orientation...



The cup faces the fluid side and missing from the far right of the pic is the rubber dust shield which goes on last. The rubber ring that is on the piston also goes cup side towards fluid.

[Ccitis]

I'll see if I can take one apart and take a pic of it.

Front master cylinder M/C orientation...



The cup faces the fluid side and missing from the far right of the pic is the rubber dust shield which goes on last. The rubber ring that is on the piston also goes cup side towards fluid.

Thanks. Thats what mine looked like. I have a rebuild kit coming, although there does not appear to be much wrong with the stock stuff. Perhaps some new seals will help. I am quite stumped!

[bikerphil]

Look inside the bore where the piston goes and look for any kind of scratches or wear. I usually clean it up with some 600 grit wrapped around a wooden dowel. If the wear is too great, a replacement would be in order.