Is it possible to modify a 13mm Master cylinder to a 20mm?

[Eccl.12vs13]

Hello all: I've been following this forum for awhile now and I'm in the middle of a K-'cafe' project. I may have jumped the gun here and bit more than I can chew, but I already bought a GSXR 1000 front end from ebay and now I'm wondering if the stock 13mm master cylinder will provide enough pressure to stop the bike.

I've since learned that a 20mm version MC was once available, but finding one is like finding the proverbial needle in a haystack. Does anyone know whether or not the stock 13mm MC can be modified to 20mm in any way, or is there a BMW right switch/brake lever that I can use in place of the stock switch/brake lever?

I have seen some USD upgrades that continue to use the stock controls and was hoping someone could give me some feedback as to whether there is enough pressure to stop the bike even in a panic stop? My riding style is back country roads early on a Sunday morning, but you can never what those darn deer's are thinking, so a panic stop may be needed every now and then.

Any help would be greatly appreciated.

R.V.

[rbm]

A standard K1100 front MC of 20mm so look for a used one of those.  That MC can actuate a pair of 4-pot Brembo's with good feedback.  A 13mm with the same callipers may feel too soft and will have a long lever pull which might not instill confidence.

[Eccl.12vs13]

Hello all: I've been following this forum for awhile now and I'm in the middle of a K-'cafe' project. I may have jumped the gun here and bit more than I can chew, but I already bought a GSXR 1000 front end from ebay and now I'm wondering if the stock 13mm master cylinder will provide enough pressure to stop the bike with the addition of the GSXR brakes.

I've since learned that a 20mm version MC was once available, but finding one is like finding the proverbial needle in a haystack. Does anyone know whether or not the stock 13mm MC can be modified to 20mm in any way, or is there a BMW right switch/brake lever that I can use in place of the stock switch/brake lever?

I have seen some USD upgrades that continue to use the stock controls and was hoping someone could give me some feedback as to whether there is enough pressure to stop the bike even in a panic stop? My riding style is back country roads early on a Sunday morning, but you can never what those darn deer's are thinking, so a panic stop may be needed every now and then.

Any help would be greatly appreciated.

R.V.

[DEcosse]

I think a 20mm might be too far the other way - lever probably going to be too hard and not much 'feel' 
I presume you're using GSXR calipers?

What are you stuck on a BMW master cylinder ?
Is this just because of the switch?
I think I'd be looking to modify the switch for use without the brake and use master from another bike (and a Radial would be best)

[Eccl.12vs13]

A standard K1100 front MC of 20mm so look for a used one of those.  That MC can actuate a pair of 4-pot Brembo's with good feedback.  A 13mm with the same callipers may feel too soft and will have a long lever pull which might not instill confidence.

Do you know whether or not the K1100 front MC be a direct fit to stock K100 levers, or will I have to purchase the entire switch/lever combination? I've been searching ebay for some time now and can't seem to find the combo. I did see that Magura? at one point made a 20mm MC direct replacement, but the website that was selling them have none in stock nor will they be getting any more.....some to due with a lawsuit.

Thanks for the reply.

[DEcosse]

About the only function on the OEM switch you won't get on most Japanese/other Euro bikes switchgear is the turn cancel switch - you can always add an additional miniature switch for that function* along with a switch of your liking

That opens up possibility for lots of different options - radial masters from Japanese or Euro - there are Brembo OEM types available (e.g. Ducati or Aprilia) or you can go with a full race-spec Brembo RCS - that's what I have on my Triumph with the GSXR front end

* You may not even need that if your OEM speed-cancel function is working;
or swap out to a Kisan signal minder 

[rbm]

If you're doing an USD swap, D'Ecosse's suggestions are worth considering. If you want the OEM controls for looks and/or ease of adapting, then also look for R850 / R1100 '93 - '02 units on ebay.  They are equivalent to the K1100 20mm units.  R-bike parts are sometimes easier to get and cheaper.

[DEcosse]

Here is a switch that will work for your requirement
https://www.ebay.com/itm/07-YAMAHA-V-STAR-XVS-1300-Right-Hand-Switch-Controls-Engine-Start-Stop-Kill/302734631143?hash=item467c63e0e7%3Ag%3ASREAAOSwrBRa9Jqt&_sacat=0&_nkw=yamaha+Run+start+turn+switch&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0%7C0



The 'select' switch is a common ground with 'up' & 'down' positions outputs (it is normally used to control functions on the speedo on that bike); and also the reset - uses the same common ground and a third output.

These could all be used to control your turn signals
Up - Right
Down - Left*
Reset - Cancel

* (You don't have to move the left over to this side, but you have that option if you want - makes it clean so all your turn functions are on that same side)

Fairly easy re-wire job

Then use whatever master takes your fancy

[Eccl.12vs13]

I think a 20mm might be too far the other way - lever probably going to be too hard and not much 'feel' 
I presume you're using GSXR calipers?

What are you stuck on a BMW master cylinder ?
Is this just because of the switch?
I think I'd be looking to modify the switch for use without the brake and use master from another bike (and a Radial would be best)

Yes...will be using GSXR calipers! I think I will first just bleed the brakes with the stock 13mm MC, take the bike for some test runs and hard braking to see how they feel. Never thought about the brakes feeling 'too' hard before.

And also, the reason for wanting to stay with stock switches is because of my limited wiring experience. But hey....now is probably the time to change that.

Thanks for the advice,
R.V.

[Eccl.12vs13]

If you're doing an USD swap, D'Ecosse's suggestions are worth considering. If you want the OEM controls for looks and/or ease of adapting, then also look for R850 / R1100 '93 - '02 units on ebay.  They are equivalent to the K1100 20mm units.  R-bike parts are sometimes easier to get and cheaper.

If I find that the stock 13mm MC are, in fact, too weak I will look for these OEM controls.

Thanks for the help,
R.V.

[DEcosse]

If I find that the stock 13mm MC are, in fact, too weak I will look for these OEM controls.

Actually the smaller the bore of the master, will actually give you higher braking force at the calipers for the same applied hand force vs a larger master.
However the problem is going to be
a) the lever will 'feel' like mush and the travel will be quite extensive (if indeed adequately long)
b) there might actually be insufficient volume in that 13mm master to supply 8 caliper pistons before you run out of stroke!

And the opposite will apply with 20mm - there will be very little travel of the lever and it will require a higher applied force with your hand (fingers)
(it gets a bit confusing with radial masters - those indeed likely have larger bores but use a different applied lever ratio - I wouldn't go beyond 19 though)

I wouldn't even bother with the 13 to be honest - but the 20 might work if you can find one

And also, the reason for wanting to stay with stock switches is because of my limited wiring experience. But hey....now is probably the time to change that.

I can help you with that:

Here is the wiring diagram and function of that Yamaha Switch assembly - even has the wire colours by terminal position in the connectors!
I have even updated it with the corresponding wire colours for the BMW in the appropriate mating connector positions
(the attachment gets reduced in size - if you decide to go this route send me PM and I'll send you larger image and more detail on the wiring colours/connector positions)

And here are the connectors you would need (simpler to replace the BMW ones and just plug this in as-is)

https://www.corsa-technic.com/item.php?item_id=343&category_id=129

https://www.corsa-technic.com/item.php?item_id=524&category_id=127


VStar_BMW_Rt_Switch.jpg (41.66 kB . 768x407 - viewed 600 times)

[DEcosse]

You may know this already:
Conventional Master types have the cylinder parallel to the bar;
Radial Masters have the cylinder perpendicular to the bar.

https://www.ebay.com/itm/APRILIA-TUONO-FACTORY-2017-Brembo-Front-Brake-Master-Cylinder/183366609340?epid=19020448180&hash=item2ab18069bc%3Ag%3AAF8AAOSwWJZbaLMF&_sacat=0&_nkw=aprilia+front+master+cylinder+&_from=R40&rt=nc&_trksid=m570.l1313

Nice Aprilia Tuono Brembo (OEM spec) Radial with reservoir (going soon though - ends tomorrow)

Quite a nice Ducati one - https://www.ebay.com/itm/2011-Ducati-Multistrada-1200-Brembo-Front-Brake-Master-Cylinder-Pump-624-4-056-1/232786556940?epid=1357340419&hash=item363328f80c%3Ag%3AQl8AAOSw3pZbDahP&_sacat=0&_nkw=ducati+front+master+cylinder&_from=R40&rt=nc&LH_TitleDesc=0

https://www.ebay.com/itm/Ducati-Front-Brake-Master-Cylinder-899-959-Panigale-NEW-oem-62440861A-62440862A/173202493069?epid=15013392300&hash=item2853ac4e8d%3Ag%3Az30AAOSwQXBaoKCi&_sacat=0&_nkw=ducati+front+master+cylinder&_from=R40&rt=nc&LH_TitleDesc=0 = <- you can pretty much get an RCS for that much!!!!

https://www.ebay.com/itm/Brembo-19-RCS-Adjustable-Folding-Radial-Front-Brake-Master-Cylinder-110A26310/162565218190?epid=1111817354&hash=item25d9a45f8e%3Ag%3As3IAAOSw3YJZTyJe&_sacat=0&_nkw=brembo+RCS&_from=R40&rt=nc&_trksid=p2047675.m570.l1313.TR11.TRC1.A0.H0.Xbrembo+RCS.TRS0

^ That's what I have

Shop around - you'll find the Nissins off the Japanese bikes are a lot less expensive than the Brembos on the Euro bikes
Just be wary of Nissins off GSXR's from about 06-16 - these were all subject to recall for corrosion in the cylinder (that's why I would say go with a Brembo)

[Eccl.12vs13]

Here is a switch that will work for your requirement
https://www.ebay.com/itm/07-YAMAHA-V-STAR-XVS-1300-Right-Hand-Switch-Controls-Engine-Start-Stop-Kill/302734631143?hash=item467c63e0e7%3Ag%3ASREAAOSwrBRa9Jqt&_sacat=0&_nkw=yamaha+Run+start+turn+switch&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0%7C0



The 'select' switch is a common ground with 'up' & 'down' positions outputs (it is normally used to control functions on the speedo on that bike); and also the reset - uses the same common ground and a third output.

These could all be used to control your turn signals
Up - Right
Down - Left*
Reset - Cancel

* (You don't have to move the left over to this side, but you have that option if you want - makes it clean so all your turn functions are on that same side)


 

Fairly easy re-wire job

Then use whatever master takes your fancy

Thanks a bunch. This could be a great options if I can't find a K1100 or similar 20mm MC. Also like the fact of having all controls on one side. For the few months I rode the 'K' it took awhile to get accustom to using both sides for operating the turn signals.

[Eccl.12vs13]

You may know this already:
Conventional Master types have the cylinder parallel to the bar;
Radial Masters have the cylinder perpendicular to the bar.

https://www.ebay.com/itm/APRILIA-TUONO-FACTORY-2017-Brembo-Front-Brake-Master-Cylinder/183366609340?epid=19020448180&hash=item2ab18069bc%3Ag%3AAF8AAOSwWJZbaLMF&_sacat=0&_nkw=aprilia+front+master+cylinder+&_from=R40&rt=nc&_trksid=m570.l1313

Nice Aprilia Tuono Brembo (OEM spec) Radial with reservoir (going soon though - ends tomorrow)

Quite a nice Ducati one - https://www.ebay.com/itm/2011-Ducati-Multistrada-1200-Brembo-Front-Brake-Master-Cylinder-Pump-624-4-056-1/232786556940?epid=1357340419&hash=item363328f80c%3Ag%3AQl8AAOSw3pZbDahP&_sacat=0&_nkw=ducati+front+master+cylinder&_from=R40&rt=nc&LH_TitleDesc=0

https://www.ebay.com/itm/Ducati-Front-Brake-Master-Cylinder-899-959-Panigale-NEW-oem-62440861A-62440862A/173202493069?epid=15013392300&hash=item2853ac4e8d%3Ag%3Az30AAOSwQXBaoKCi&_sacat=0&_nkw=ducati+front+master+cylinder&_from=R40&rt=nc&LH_TitleDesc=0 = <- you can pretty much get an RCS for that much!!!!

https://www.ebay.com/itm/Brembo-19-RCS-Adjustable-Folding-Radial-Front-Brake-Master-Cylinder-110A26310/162565218190?epid=1111817354&hash=item25d9a45f8e%3Ag%3As3IAAOSw3YJZTyJe&_sacat=0&_nkw=brembo+RCS&_from=R40&rt=nc&_trksid=p2047675.m570.l1313.TR11.TRC1.A0.H0.Xbrembo+RCS.TRS0

^ That's what I have

Shop around - you'll find the Nissins off the Japanese bikes are a lot less expensive than the Brembos on the Euro bikes
Just be wary of Nissins off GSXR's from about 06-16 - these were all subject to recall for corrosion in the cylinder (that's why I would say go with a Brembo)

Thanks for the advice and all of the info. With some help from a member on another forum I was able to buy this MC switch combo on ebay:

https://www.ebay.com/itm/1994-94-97-BMW-R1100RS-1100-RS-OEM-RIGHT-HANDLEBAR-SWITCH-MASTER-CYLINDER-CABLES/323342679329

Hope I will be able to make this all come together.

Will post pics as project comes along.....still breaking it down, buying parts and trying to see which direction I want to go with it.

Thanks again,
R.V.