Brakes?

[sscuba78]

Where can I find new resavoirs for my front and rear brake.

[scoobes]

brakes

you could check out the fj1100 front brakes,as alot of the front end stuff of the fj has been put on my mates 1.1s.dont know about the back one yet .scoobs

[Geezer]

Yamaha never sold them separately. I found this out the hard way when trying to buy a replacement o-ring that goes under the reservoir on my 1980 Mongrel. They never sold that O-ring separately either.

The parts books didn't show any break-down for the master cylinder body.

Geezer

[sscuba78]

would a H-D setup work atleast for the front?

[TopCatGr58]

Egads, Harley parts on an XS, perish the thought!!!!

But all kidding aside, as long as the supply line is 10MM mounting and you can get a good seal, it should work.....but Harleys usually have a 1" diam handlebar, and the XS is 7/8", so it might not clamp onto the handlebars without some modification, putting some sort of spacer inside the clamp to take up the 1/8" difference!?!? Let us know if you do it, and how it works out!

T.C.

[wildbill]

brakes?

I had to replace front master cylinder on my bike.I was at a shop that had alot of junked out bikes.Looked around,finally found a good one off a Honda V4 cruser that worked.Had to change brake light hookup by spliceing the wires.The stock mirror won`t work so settle for Honda mirror.Well it looks crudey but at least I have front brakes.

[fusionking]

One would need to make sure the piston was the same or smaller size or you'll have less braking power......Just anything that bolted up could cost you your life in the exact wrong scenerio!!(you don't want to extend your stopping distance....keep it technical and safe, esp. if you ride 2-up)

[xssiveone]

Originally posted by fusionking
One would need to make sure the piston was the same or smaller size or you'll have less braking power......

I'm curious, why "smaller"? I'm no expert on brake systems or hydraulic systems either, but I would have thought that a larger piston would have displaced more fluid, thereby forcing the caliper piston out further, and creating more braking power. Am I misunderstanding things here?

[mitch]

Yup !!!

Your master cyl piston , lets say only moves 1 cubic centimeter of fluid when you pull the lever. If the hole it has to fill is larger it will not push the piston out very far as it takes more fluid to fill the larger hole HTH.....MITCH

[Hobbit]

In order to move more fluid for the same amount of brake lever travel you need a larger diameter master cylinder. That's why the master cylinder on a XS11 has a larger dia than a single caliper system.

If you move the lever 10mm and displace 1cc of fluid (the numbers are strictly hallucinations, I don't do that kind of math), a larger dia master cylinder will move more fluid for the same amount of lever travel.

This web site has some good basic information on hydralics.

http://auto.howstuffworks.com/brake3.htm

[CMA1]

I met a guy from another town near me with a '80 Special.
He had installed a Master Cylinder and all, from a '83 or '84 Kawasaki LTD.... it seemed to work fine. He said the piston (and lever I guess) had a little more travel than the OEM, but with some adjustment he made it work. Just FYI.
CMA1

[xssiveone]

Re: Yup !!!

Originally posted by mitch
Your master cyl piston , lets say only moves 1 cubic centimeter of fluid when you pull the lever. If the hole it has to fill is larger it will not push the piston out very far as it takes more fluid to fill the larger hole HTH.....MITCH

That was what confused me... he said the piston should be

the same or smaller size

I couldn't understand how a smaller master cylinder piston could equal or improve braking performance.

[TheDjost]

If you move more fluid per mm of travel, you will need to apply more force on the lever to give the same amount of force on the brake caliper piston.

It's in the multiplication that it's all located. Think about it: how much do the pads move? How much does the lever move? If tou use a larger piston, the lever will move less than it did, so the ratio of pad movement to lever travel has gone down, as did power capacity.

In short, if you go bigger master, you better have good knuckles!

Same thing as changing a rear sprocket on a chain drive bike.

-Justin

[TopCatGr58]

Hey there Brian and others,

I thought about jumping in here when I first read FusionKing's statement about needing a smaller piston.....cause it wasn't totally clear as to which piston he was referring to!! He meant that you needed to find another master cylinder that controlled a disc brake system that used the same size or smaller "caliper piston...not a smaller 'master cylinder' piston! It was stated a little ambiguously. No offense !!!!

Our front caliper pistons are fairly large compared to the more modern smaller dual piston configs, and seem to require more fluid to actuate them, hence the large master cylinder pumping plenty of fluid. I got a different MC from a newer Yamaha bike when mine was totally trashed but didn't realize about the need for so much fluid, and so mine are a bit softer, have to squeeze a bit more and farther to get them to work as effectively as the OEM's did. But I was in a budget/time crunch at the time. Wish I had saved my old MC!
T.C.

[fusionking]

You read it right!!

Sorry guys i've been away... but I see you'all haven't! I was referring to the master cyl. It is a matter of PSI not fluid volume and it is the ratio of the area of one piston to another. On your car, all things being equal, if you installed a manual master cyl on a power booster it will practically throw you thru the windshield!(BTDT) When racing stock cars , matching caliper sizes to master cyl. sizes is normal everyday stuff. It also helps to know this sorta stuff if you build or restore old cars. You can increase brake presure by increasing the caliper piston size or decreasing master cyl piston size either way does the same thing. If you look at HARD CORE stock-car supply co. catalogs you will find brake-pres. gauges for sale. It is something you must deal with separately at each end just like a bike. On my late Model asphalt car I ran 3 calipers (2 front 1 LR) and 2 master cyl with a balance bar to prevent rear wheel lockup and to even be with-in adjustment range I had to run a Bigger MC piston on the rear! If you sleeved yor XS master cyl. and left the caliper the same size you gain PSI. If you sleeved your caliper and left the master cyl the same you'd lose PSI. I know people can and do get away with breaking simple rules everyday but I believe that if you are going to modify something...... esp. brakes... then IMPROVE them!!!