Master cylinder bore clean up, plastic reservoir removal?

[Its been a long time]

Good morning, having stripped the XS650D master cylinder down this morning, as expected, it's really mucky. Pretty much as per other people's findings that they've posted.
Question is, best way to clean up the 14mm bore of the cylinder? Has anyone used a 14mm diameter brass brush? Used in my electric screwdriver/drill I can control the speed down to really slow. I think lubricating the brush and pasing it gently up and down the bore will do the job. Anyone done that? I don't want to wreck the bore but it needs a good clean.

Secondly, the plastic reservoir definitely isn't moving. It's been soaking for a couple of days in release oil having splayed the joint a little and squirted oil in the crevice and inside the master cylinder reservoir. I can't find any replacement for the reservoir, it seems the 14mm Nissin master cylinder reservoir was never available as a spare?

Thanks.

 

[atom4488]

I believe the master is cast aluminum, so the brass brush bristles are quite likely to be harder than the bore material. |If the bristles were very fine and the whole thing was well lubricated, it may be OK. I would proceed with caution. I have no experience with removal of the reservoir, so I can't comment.
IMO, unless it is important to you to preserve and use the original MC, I would consider a generic replacement. They are available very cheaply and of good quality, in a variety of bore sizes so that you can optimize your front brake feel.

 

[Its been a long time]

I believe the master is cast aluminum, so the brass brush bristles are quite likely to be harder than the bore material. |If the bristles were very fine and the whole thing was well lubricated, it may be OK. I would proceed with caution. I have no experience with removal of the reservoir, so I can't comment.
IMO, unless it is important to you to preserve and use the original MC, I would consider a generic replacement. They are available very cheaply and of good quality, in a variety of bore sizes so that you can optimize your front brake feel.

Fully understood. I am naturally sceptical about these very low cost master cylinders. They'll be 100% chinesium and while everything is these days, I'm not sure how I know I have a decent quality one. And I definitely want the left had thread mirror mount that isn't always present.

 

[gggGary]

to clean up the bore. I take about 8" of 1/2" wood dowel, slit it lengthwise about 2" with a coping saw. cut a small square of 1000 grit wet or dry sand paper and slip it in the slot wrap so it faces out. with a bit of water work it up and down and rotate inside the bore.

I've probably done 10 MC's with that stick lol
This type of MC reservoir?

I'll lightly clamp the MC in the vice then grab the plastic with both hands or a big slip joint pliers and a rag and twist.

 

[Its been a long time]

to clean up the bore. I take about 8" of 1/2" wood dowel, slit it lengthwise about 2" with a coping saw. cut a small square of 1000 grit wet or dry sand paper and slip it in the slot wrap so it faces out. with a bit of water work it up and down and rotate inside the bore.
View attachment 257030
I've probably done 10 MC's with that stick lol
This type of MC reservoir?
View attachment 257029
I'll lightly clamp the MC in the vice then grab the plastic with both hands or a big slip joint pliers and a rag and twist.

Thanks. I'll give that a try on the M/C bore. If that cleans up, it'll be do or die with the plastic reservoir. I don't trust a 47 year old piece when it's been as neglected as this one has.

 

[Its been a long time]

Well, the original 14mm master cylinder is corroded beyond use. The bore is so corroded, the circlip groove has corroded away once it's cleaned up.

I'm going to use one of the EMGO 13mm master cylinders that are widely available.

 

[gggGary]

Long as you're changing go 11mm and ss line. you won't regret it.

 

[Its been a long time]

Long as you're changing go 11mm and ss line. you won't regret it.

Thanks. Measure up for braided brake line is next on the list to do.

 

[gggGary]

I use these;

ebay search; (xt225,tw200) master cylinder

 

[arcticXS]

I use the "coffin" reservoir type Brembo MC on both my XS and RD.
I believe a new one can be found for 100-120 USD. Only drawback is the mirror thread, it is RH, while OEM Yamaha is generally LH on the brake side. But you can find suitable mirror adapters.

 

[Melnic]

Moot point for you at this juncture but FYI, I use a 20 gauge shotgun cleaning mop on my MC. It will squeeze down to 14mm
I put some fliz (fine polishing compound) on it and a drill. This was after using cleaning chemicals (mineral spirits, hoppes 9 etc) to clean it out.
Often I will soak the MC in a tub of mineral spirits I have on the ready. As you can tell, I dabble in old C&R milsurp guns so I have those things handy all the time.

 

[Its been a long time]

Moot point for you at this juncture but FYI, I use a 20 gauge shotgun cleaning mop on my MC. It will squeeze down to 14mm
I put some fliz (fine polishing compound) on it and a drill. This was after using cleaning chemicals (mineral spirits, hoppes 9 etc) to clean it out.
Often I will soak the MC in a tub of mineral spirits I have on the ready. As you can tell, I dabble in old C&R milsurp guns so I have those things handy all the time.

Thanks. Master cylinder bore has cleaned up as best possible and is generally a mm or more oversize due to corrosion and it is still pitted. The circlip groove is crumbled away to almost nothing. The only way this master cylinder bore is going to be usable again is boring it oversize and shrinking a sleeve in. That's for another day.

 

[Its been a long time]

A quick post to close out this thread and hopefully post a bit of useful information for others this side of the Atlantic.

After looking for good used Yamaha front master cylinders I gave up since I wouldn't use a second hand master cylinder without overhauling it. The cost of a good used one plus an overhaul kit was around the same as a new front master cylinder I bought from Yambits here in the UK.

Yambits don't list a front master cylinder for a 1977 XS650D. But I was recommended to buy one listed for a RD250LC. Which I did. It turns out to be an EMGO item. It's 12.7mm bore and has the correct Yamaha left hand thread mirror mount. It comes with a front brake light switch too. Looks fair quality and I suspect it's identical to items listed by other XS650 parts resellers at about 2x the Yambits price.

This is what I bought -

https://yambits.co.uk/rd250lc-brake-master-cylinder-p-102942.html

 

[5twins]

That 12.7mm bore size you got is actually a 1/2". I have a used Yamaha one on one of my bikes, an 11mm on the other. The 12.7mm size will give you slightly better "feel" and brake modulation than the original 14mm size, but not as much of an improvement as the 11mm would.

Some things I like about used original Yamaha units are the quality, they take an original reverve thread mirror, use the original brake light switch and lever.

 

[Wingedwheel]

I used this line and couldn’t be happier. Just make sure you get one an inch or so longer than you think you need….

https://www.amazon.com/gp/product/B09WYG79R6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[Its been a long time]

That 12.7mm bore size you got is actually a 1/2". I have a used Yamaha one on one of my bikes, an 11mm on the other. The 12.7mm size will give you slightly better "feel" and brake modulation than the original 14mm size, but not as much of an improvement as the 11mm would.

View attachment 258790


View attachment 258791

Some things I like about used original Yamaha units are the quality, they take an original reverve thread mirror, use the original brake light switch and lever.

Thanks, I deliberately chose the 1/2" - 12.7mm master cylinder because I like less rather than more lever travel. But it will provide a better feel at the lever compared to the original 14mm one.

The EMGO master cylinder I have has the left hand thread mirror mount and the brake switch looks the same as the Yamaha one. I don't know if the lever on the Yamaha master cylinder and the EMGO one are interchangeable.

 

[5twins]

Yes, the 12.7mm one will give less lever travel than the 11mm one, that's the big thing I like about it. It has hardly any more travel than the original. But, it doesn't give anywhere near the improvement in "feel" compared to the 11mm unit. I have a couple more used 11mm ones I picked up cheap off eBay and may swap one on in place of the 1/2" once I renovate them. It's not easy to find nice used 11mm units because most come from dirt bikes and are pretty beat up, lol. But if you're patient, one will pop up eventually.

 

[arcticXS]

According to the Vintage Brake (MMM) caliper/ master cylinder ratio chart, 11 mm MC is spot on for one 38 mm single piston caliper (77 and newer), while a 13 mm MC is ideal for one of the earlier 2x48 mm piston caliper. So a 13 mm Brembo MC is what I have on my RD350, and also on the XS which has one 4x34 mm Brembo caliper. Both bikes have a great front brake.

When upgrading to a more suitable MC size, the maximum brake line pressure will increase, so upgrading to quality, modern brake lines is absolutely required. Going from a 14 mm to a 11 mm MC will give 62% more pressure for the same lever pull, all other things being equal!

 

[Its been a long time]

According to the Vintage Brake (MMM) caliper/ master cylinder ratio chart, 11 mm MC is spot on for one 38 mm single piston caliper (77 and newer), while a 13 mm MC is ideal for one of the earlier 2x48 mm piston caliper. So a 13 mm Brembo MC is what I have on my RD350, and also on the XS which has one 4x34 mm Brembo caliper. Both bikes have a great front brake.

When upgrading to a more suitable MC size, the maximum brake line pressure will increase, so upgrading to quality, modern brake lines is absolutely required. Going from a 14 mm to a 11 mm MC will give 62% more pressure for the same lever pull, all other things being equal!

Yes, the old two piece rubbery hoses are being replaced by one braided hose.