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Old 01-13-2011, 03:43 PM   #1
i dig boogers OP
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bmw master cylinder suggestions???

i have a '76 r90/6 that has a dual disc setup on it. the master is leaking severely and upon inspection is pitted beyond honing.
i was thinking of...

(1) having it re sleeved (locally $120) but to go with 17mm or 14mm (word is that size works better?) new piston is the question there. plus its a lot of $ for not giving an upgrade.

(2) getting a post '85 (what i heard was the easiest swap?) handlebar mount master. if someone has more specific suggestions for which model to use for the swap that would be helpful.

(3) finding a used master that isnt pitted

(4) finding a used single cylinder (14mm?) master and have it tapped for a second line (not sure of cost or if its a possible home job)

ive been researching for a while and havent come up with a very good solution yet considering this bike has nickel and dimed my resources but this is the last (fingers crossed) issue i have to deal with so i may just put whatever i need on a card and deal with it later! (aka the american way).

any input would be greatly appreciated, thanks,
-idb
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Old 01-13-2011, 03:57 PM   #2
SOLO LOBO
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Regardless of what option you dp pick, it may be worth your time checking out motobins in the UK, they have great prices for new parts and ship fast.

I got a new master cylinder for my '81 G/S for something like $120, and it delivered in less than a week.
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your bike is suitably dirty. Well done.
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Old 01-13-2011, 04:00 PM   #3
blaine.hale
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I'll second the motobins suggestion. Buy a new one for roughly the same price as getting that one re-sleeved and you'll have piece of mind. That fluid will destroy your frame (it pitted min really bad.)
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Old 01-13-2011, 04:06 PM   #4
vacantstare
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I posted part numbers in this thread:
http://www.advrider.com/forums/showt...ht=agonizingly

for a bar mount master cylinder and some of the other parts you'd need if you decide to go this route.
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Old 01-13-2011, 07:11 PM   #5
wirewrkr
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Quote:
Originally Posted by SOLO LOBO View Post
Regardless of what option you dp pick, it may be worth your time checking out motobins in the UK, they have great prices for new parts and ship fast.

I got a new master cylinder for my '81 G/S for something like $120, and it delivered in less than a week.
Yeah, but that's just for the master portion itself.
He will need the whole enchilada as he currently has the under tank style.
Quite a bit more $$$.
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Old 01-13-2011, 08:31 PM   #6
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hmmm, when i looked up the current under tank m/c from motobins it is $354, the handlebar mount kit with a hose and splitter is $380. where are these $120 ones?!?

@vacantstare good info and research. btw how much was your bmw bar mounted m/c and what year/mocel is it too?

anyone ever put on a single throttle pull jap m/c and lever then use a cable splitter? seems the only issue would be finding correct ratio unless those splitters dont perform well.
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Old 01-13-2011, 10:17 PM   #7
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Another option...look for 2nd hand from a mono 800...13mm mc.
Ss lines while you're at it.
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Old 01-13-2011, 10:25 PM   #8
SOLO LOBO
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Quote:
Originally Posted by i dig boogers View Post
hmmm, when i looked up the current under tank m/c from motobins it is $354, the handlebar mount kit with a hose and splitter is $380. where are these $120 ones?!?
ell, if you look at the R80G/S ones you will find the $120 ones...



Quote:
Originally Posted by i dig boogers View Post
anyone ever put on a single throttle pull jap m/c and lever then use a cable splitter? seems the only issue would be finding correct ratio unless those splitters dont perform well.
bgoodsoil did on his G/S that has a Suzuki front end... perhaps not the answer you were looking for.
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your bike is suitably dirty. Well done.
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Old 01-14-2011, 12:14 AM   #9
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Quote:
Originally Posted by boxerboy81 View Post
Another option...look for 2nd hand from a mono 800...13mm mc.
Ss lines while you're at it.
would that be an f800? and whats the consensus on going with a lower mm piston? in the mean time im thinking of just picking up a single caliper m/c and tap it until i save up or make a better informed decision
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Old 01-14-2011, 12:27 AM   #10
boxerboy81
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Quote:
Originally Posted by i dig boogers View Post
would that be an f800? and whats the consensus on going with a lower mm piston? in the mean time im thinking of just picking up a single caliper m/c and tap it until i save up or make a better informed decision
R80 85-87 or the other R100 mono variants. They had 13mm mc, then part way thru '89 they changed to 14mm.

The higher the number, the shorter the lever movement, but the more abrupt the braking. This is a twin disk, handlebar setup.

I went from a 15mm on my '82 RS to a 13mm and like the improvement in feel.
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Old 01-14-2011, 06:36 PM   #11
i dig boogers OP
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any advice on tapping a single caliper m/c? thanks for all the input to far!
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Old 01-14-2011, 06:42 PM   #12
brentde3
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+another for motobins. I got a magura handlebar mounted master cylinder for my '76 r90/6. It came with a splitter, so one assumes that it could be made to work with a dual-disc setup.

http://www.motobins.co.uk/bmw-parts....20valve%20Twin

Use the dropdown menus to select brakes and handlebar master cylinder kits. Their currency converter says it's $381. Spendy, but cool.
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