somehow that seal looks wrong. did it get flipped inside out? IIRC there should be a thin edge facing towards the spring?
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I don't know, it was like that when I took the piston out, except it was in the middle of the piston. I just slided it back to the left, where it is supposed to be. Something tells me yours is slightly more coned shaped as well. Images in the manual or on the net name it "cup", but due to old, small and graphic images it's hard to tell how it supposed to look like. I'll try to take it off and check. Thanks for poiting it out.
EDIT: Before unmounting the piston from the cylinder, it was easy enough to press the piston in with the lever or hand. So it was only the washer that made it difficult to remove the piston.
This is why I'm so glad to be a member of this forum.
If you still have it unmounted, could you, or some else, post a picture of it, if possible, from different angles. And did they perhaps also change the style of it over the years.
EDIT: Before unmounting the piston from the cylinder, it was easy enough to press the piston in with the lever or hand. So it was only the washer that made it difficult to remove the piston.
This is why I'm so glad to be a member of this forum.
If you still have it unmounted, could you, or some else, post a picture of it, if possible, from different angles. And did they perhaps also change the style of it over the years.
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So i took the rubber seal off.This is what it looks like from different angles. It seems to be right. And not turned inside out, since there is a groove inside the seal that fits on the spline on the piston.
But, does everything else looks normal? And why could I, before unmounting the snap ring, washer, piston, spring etc, with ease press the piston in with lever or hand (except for the spring tension). Could it have swollen? Before unmounting I had to spray som wd40 on the snap ring and washer to get them loose. Maybe it it got in and on the rubber. Don't know what else could have happen...
And if it has swollen, is there anything one can do to get it to shrink? Or must I order a whole rebuild kit, since they don't seem to sell only the rubber parts.
But, does everything else looks normal? And why could I, before unmounting the snap ring, washer, piston, spring etc, with ease press the piston in with lever or hand (except for the spring tension). Could it have swollen? Before unmounting I had to spray som wd40 on the snap ring and washer to get them loose. Maybe it it got in and on the rubber. Don't know what else could have happen...
And if it has swollen, is there anything one can do to get it to shrink? Or must I order a whole rebuild kit, since they don't seem to sell only the rubber parts.Attachments
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PLease help me out, I'm confused...
I found this rebuild kit for the M/C, but the OD seems wrong. My piston is 20 mm OD, 12/13 mm ID and 55 mm long. The cylinder bore is also 20 mm.
The rebuild kit piston is 55 mm long, but has OD 17,3 mm. It says that the kit is for 75-76 twin disc model.
http://www.wemoto.com/bikes/yamaha/...brake_mastercylinder_-_front_-_tourmax_japan/
At mikesxs and xs650shop they sell a rebuild kit that looks the same, 17 mm OD, but for XS650 Standard 1977-79, XS650 Special 1978-84.
Can anyone confirm that the OD for 75B M/C piston should be 20 mm. I seem to have the original M/C for dual disc.
I can't find any rebuild kit for my M/C that is a bore 20 mm
I found this rebuild kit for the M/C, but the OD seems wrong. My piston is 20 mm OD, 12/13 mm ID and 55 mm long. The cylinder bore is also 20 mm.
The rebuild kit piston is 55 mm long, but has OD 17,3 mm. It says that the kit is for 75-76 twin disc model.
http://www.wemoto.com/bikes/yamaha/...brake_mastercylinder_-_front_-_tourmax_japan/
At mikesxs and xs650shop they sell a rebuild kit that looks the same, 17 mm OD, but for XS650 Standard 1977-79, XS650 Special 1978-84.
Can anyone confirm that the OD for 75B M/C piston should be 20 mm. I seem to have the original M/C for dual disc.
I can't find any rebuild kit for my M/C that is a bore 20 mm
yeah us el norte americano's aren't a real big help here. I don't think we ever got that MC. Will the seal fit in the bore without the piston? Swelling sure is possible I have ruined a few rubber brake parts with petroleum products and even brake parts cleaner. once it swells it never goes back. I have checked swelled parts months and even years later they were still too big. Why I cautioned way back about 50 posts ago when this was a caliper thread. lol
for what it's worth these early brakes usually had MCs that were too big, a smaller MC with SS lines may improve your braking feel.
http://www.vintagebrake.com/mastercylinder.htm
http://www.vintagebrake.com/mastercylinder.htm
I bought Part #08-0204 from Mikes for my Australian, 80SG Duel front disk model Master-cylinder. This is the 20 mm one. Just checked the package part no with the saved original old parts
5twin, I used brake cylinder grease (silicone based) on both rubber and bore. Thought it would be enough greasy...
650Skull, maybe it's the same M/C then. I measured the rubber, it's 20 mm at one end and 22 mm the other (since cone shaped). If you have yours unmounted, could you measure it? Then I would know if mine has swollen or not.
gggGary, I read some interesting threads about the size of the M/C versus the caliper bore and amounts of caliper. Don't kow what the intersection results of the X/Y axle stands for in the chart. The ratio? Would my setup (48 mm caliper, 4 active pistons and a m/c bore 20 mm) then resul. in approx ratio 20-25:1 (for 19 mm and 48 mm caliper and 4 active pistons it is 25.53).
EDIT: Found the thread... xsLeo recommends 16 mm bore for early caliper (2 piston) twin disc setut. In the chart that would be 36.00. http://www.xs650.com/forum/showthread.php?t=11635&page=2
For this season I would like to just get it working and feel the difference. But I have been thinking of upgrading both calipers and discs, so I want to wait with changing the M/C and hoses until I know which caliper and disc I will use.
I have also ordered new rubber seals for the caliper, which will make a good improvement for sealing the calipers.
650Skull, maybe it's the same M/C then. I measured the rubber, it's 20 mm at one end and 22 mm the other (since cone shaped). If you have yours unmounted, could you measure it? Then I would know if mine has swollen or not.
gggGary, I read some interesting threads about the size of the M/C versus the caliper bore and amounts of caliper. Don't kow what the intersection results of the X/Y axle stands for in the chart. The ratio? Would my setup (48 mm caliper, 4 active pistons and a m/c bore 20 mm) then resul. in approx ratio 20-25:1 (for 19 mm and 48 mm caliper and 4 active pistons it is 25.53).
EDIT: Found the thread... xsLeo recommends 16 mm bore for early caliper (2 piston) twin disc setut. In the chart that would be 36.00. http://www.xs650.com/forum/showthread.php?t=11635&page=2
For this season I would like to just get it working and feel the difference. But I have been thinking of upgrading both calipers and discs, so I want to wait with changing the M/C and hoses until I know which caliper and disc I will use.
I have also ordered new rubber seals for the caliper, which will make a good improvement for sealing the calipers.
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I tried using more lubricant, which seemed to improve it and make the piston slide easier. But still not like before. Could be that when the M/C is completely filled with brake fluid it will make the piston slide even easier, since it will be drowned constantly by fluid, both when pressing in and retracting by the spring tension.
marp86, In an earlier post you asked about replacing the square section o-ring with a regular round section o-ring. This won't work well. The square section ring flexes as the piston moves when you pull the lever. This flexing is what pulls the piston back when you release the lever. This lets the pads release the rotor. Prevents drag. If the piston has to move very far it will slip through the square 0-ring but maintain the flex so it can return. This allows the brakes to self adjust for pad wear.
With a round o-ring the piston will just slip through the o-ring and not be pulled back.
Leo
With a round o-ring the piston will just slip through the o-ring and not be pulled back.
Leo
Yes, I think your right. Quite a smart invention. Thanks for pointing it out. I ended up ordering regular square ones for the caliper model. I intend to reuse the old pistons, but might as well end up having to buy new ones.
What do think about these affordable caliper pistons? Stainless steel as well. They seem a little thinner though. But would that really be a problem? The company seems reliable.
http://www.ebay.co.uk/itm/Yamaha-br...460285?hash=item5b20a1373d:g:oKEAAOSwPhdU2IJO
http://www.ebay.co.uk/itm/Yamaha-br...460285?hash=item5b20a1373d:g:oKEAAOSwPhdU2IJO
Thank you, din't brak any of the vital part while taking it apart. We'll see how it work when putting everything together again. Am a little concerned about the middle rubber seal and the pitting the lever bolt makes in the end of the piston.
I talked to the guy at local workshop who said that the pittings in the pistons (see first post) were at most approx 0,1 mm. What about grind the pistons down 0,1 mm? Would it seal with 47,8 mm instead of 48 with new rubber seals?
Anyone tried this?
Anyone tried this?
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Hi marp,
0.1mm less piston diameter will give significantly less squeeze on the seal.
Will the seal work with a less than designed amount of squeeze?
I have no real idea.
But while there's times when it don't matter to be cheap, I don't think this is one of them.
0.1mm less piston diameter will give significantly less squeeze on the seal.
Will the seal work with a less than designed amount of squeeze?
I have no real idea.
But while there's times when it don't matter to be cheap, I don't think this is one of them.
I was thinking that since some people with success have reused pistons that have had some pittings, this could be an option to smoothe out the surface better.
I don't know much about brakes, so that's why all these questions. And I'm am extremely grateful for all answers and good thoughts. And I don't want to cut down on safety.
The new rubber seals arrived today, so now I will have to decide to reuse the pistons or buy new ones before.
Did you read my question about the new stainlesss steel pistons four posts up? I don't know if it's the image that fools me, but the wall seem a little thinner than original. But since they are steel, would a small difference really matter? The shop seems reliable and the price is right. Shipment to Sweden costs almost half the cost, though. That's why I'm looking for good deals.
I don't know much about brakes, so that's why all these questions. And I'm am extremely grateful for all answers and good thoughts. And I don't want to cut down on safety.
The new rubber seals arrived today, so now I will have to decide to reuse the pistons or buy new ones before.
Did you read my question about the new stainlesss steel pistons four posts up? I don't know if it's the image that fools me, but the wall seem a little thinner than original. But since they are steel, would a small difference really matter? The shop seems reliable and the price is right. Shipment to Sweden costs almost half the cost, though. That's why I'm looking for good deals.
