master cylinder ID and rebuild

[gray am I]

I am wanting to get my master cylinder rebuilt But I am having doubts about which kit to use. Its an Australian delivered 78 special, twin disc, vin prefix 447-911, are there kits available or, am I going to have to get it pulled apart and buy single items.

 

[650Skull]

I got this one http://www.mikesxs.net/parts/yamaha...84-oem-1j3-w0041-20-2g2-25850-01-3j6-25850-00 for the twin Disk models from 77-84, from MikesXS, there may be some cheaper ones on the net or evilbay.

Rear M/C kit, http://www.mikesxs.net/parts/yamaha...-1j3-w0042-50-00-1j3-20000-50-2mo-25850-50-00

Freights a killer so buy a lot of small stuff and make up to the weight of about 1lb, (if my memory serves me), and the freight doesn't go up. Best to sign in, then the weight and price will tell you. You can go back and forth adding on or removing stuff and check the freight for weight.

 

[gray am I]

thanks looked at the link, listed 80 sg twin disc and other models, couldn't see that it listed mine, xs sf
Took the master cylinder started pulling it apart ( need some really long thin circlip pliers) off and noticed it had ( nissin 11/16 ) on the underside of it.
As I am going to get this repainted in the original satin black any suggestions as to the best coating? epoxy, 2 pack or powdercoat?

 

[650Skull]

447-911 makes it a 79SF and the master-cylinder components are the ones i linked to. US models did not have twin disk models from the Factory

From MikesXS site
Front Brake Master Cylinder Rebuild Kit - OEM # 1J3-W0041-20 to fit optional Dual Disc on 1980 XS650SG - Master Cylinder - OEM# 2G2-25850-01 & 3J6-25850-00 XS650 Standard 1977-79, XS650 Special 1978-84.Note: This Master Cylinder is the same as used on 1979-81 XS1100 models with Dual Disc or offered as original on some 1977-84 XS650 models (3J6 master assy.)Same as used on XS750 Standard 1977-79, XS750 Special 1978-79, XS850 Standard and Special 1980-81, XS1100 Standard and Special 1978-81.

I assure you these are the right ones.

Disassemble and clean up the M/C before buying the kits. I found mine weren't that bad after a clean but had already bought the kits, so kept the old ones for another model i have that may need a rebuild

 

[gray am I]

Ok, rebuild kit arrived from mikes xs, and I've had the master cylinder sleeved in stainless steel but I am having trouble in fitting the reservoir back on, I cannot get the reservoir to fit back into the o ring , is there a trick to this . At the moment I have the o ring in the m/c body and am trying to push the reservoir in to it , twist it in, and while holding it together pushing the o ring up into the groove . I have looked at putting the o ring onto the plastic reservoir but I don't think it will fit in that way?

 

[littlebill31]

Yours is a "Special" m/c. It's angled.
They can be tricky to get onto the O-ring. You can use a little lube, a very small amount, and put it on the o-ring to make it slide better.
Make sure the o-ring groove is very clean.

 

[gray am I]

So putting the o ring into the body first ok ? suggestions for a lube ? grease ,oil, Vaseline, I am using dot4 fluid,

 

[Paul Sutton]

With that style master cylinder you usually find a lot of crud under the plastic reservoir around the large o-ring which leads to weeping and paint damage. The plastic reservoir will lift out with a bit of twisting and gentle levering but be aware that the big o-ring behind seems to be unavailable now. As 650Skulls said the actual piston seals may still be usable as were mine. With the piston out I polished the bore with Autosol. There was a little corrosion but this was not on the surface where the rubber seal moves.

With master piston seal kits there seem to be two types, one with the smaller seal already installed in the middle of the piston and the other you must fit it yourself. They are buggers to get on. I was able to get mine on by making a 40 - 50 mm taper in the lathe with the larger end matching the diameter of the piston where the small reed valves are and the diameter at the other end to allow the seal to slide on. I then polished it really smooth with Autosol, lubricated it with DOT4 and then placed the seal on the narrow end and slid it down the taper and onto the piston. I would probably clamp the piston and taper in a vice next time because the DOT4 makes things quite slippery. There is probably another way to do it but this was my method.

Regarding paints for brake fluid resistance, I have not used them but have seen some in the past and they were two pack epoxy systems. If you want it to look nice then maybe visit a powder coat expert. Their systems are effectively two pack in that the hardener is extruded with the coating prior to being powdered and they do not cure until heated. Often these are epoxy systems but I last sprayed powder coatings 20 year ago when there was a very good chemical resistant system that was being phased out due to toxicity (Polyester/TGIC??). May still be available.

I repainted mine with conventional matt black auto spray and just make damned sure I do not spill any brake fluid.

 

[gray am I]

I was going to get it painted satin 2 pack but when they resleeved the master cylinder they blasted and painted it in a satin black without my knowledge, no charge so I couldn't complain, saved me $50 although not 2 pac. The middle seal is all ready on the piston waiting to be inserted into the bore, I just need to fit the reservoir to the body but the o ring will not slip over the lip and was looking for some tips on how to fit it.

 

[littlebill31]

That big o-ring is a pain. It gets caught up and twisted. Just use a little light lube or brake fuid to lubricate it.
You can try either putting it on the body or in the groove first.
I did have luck one time with a very thin feeler gauge to help slide it around and press the o-ring into the groove at the same time. But you can cut the o-ring also if not careful.

 

[Paul Sutton]

I would have expected the reservoir to just push back in but the design does not allow this. For some reason there are no smoothed edges to help this. I wiped a very small amount of DOT 4 on the o-ring and around the metal where the o-ring sits and then set the o-ring in the metal body. Lay the assembly on some cloths, to protect the paint fron scratches, place on a firm surface and just push the reservoir down very firmly and it will snap into place. It is as hard/easy to get off as to put back on but make sure the o-ring is wet with fluid because you do not want to damage it.

Good luck.

 

[gray am I]

finally got the seal in , used a small bent screwdriver the push the o ring up into the groove from the inside of the reservoir, took the front wheel of and got a new tyre fitted , bled the brakes. Now I've noticed that the spring clip on the front master cylinder switch is broken, I would just glue it in but the switch is not working either, and to top it off when I was checking the rear brake light the rear brake has locked on again.

 

[littlebill31]

Well, at least you got some stuff done. The bent screwdriver is similar to the feeler gauge I used. Works well.
You can get a replacement switch for the light. They get old and break. Not sure what the options ar in Australia though.