Master Cylinder

Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

I'm considering changing the MC on my bike (Yamaha FZX250 Zeal). Will any MC fit as long as I get the right banjo bolts. I plan on changing to braided lines with the new MC.

The reason I want to change is because the standard set up isn't adjustable and doesn't seem to have enough power. I like to brake with two fingers but when braking hard the lever will pull to my fingers meaning I have to get them out the way and use all 4 fingers. I want something with a lot more power but I'm not sure what to get. I've had a quick look at eBay but I don't want to buy something worse than what I have.

Thanks, Carl

Edit: should have mentioned I need it to have the bracket and lever as well.
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Quick answer is no.

Longer answer is possibly. A caliper will need a certain amount of fluid to push the pistons out and push the pads onto the disk. More pistons / larger pistons mean more fluid is required. Master cylinders use different size bores to push out different amounts of fluid for the amount of movement of the master cylinder piston. Also the relationship of the brake lever pivot point to your fingers and the master cylinder piston will change the ratio of movement of your fingers to movement of the piston.

Add to that worn seans, sticking calipers and old and knackered fluid all change how the brakes feel. Personally I would be inclined to strip and rebuild the caliper first. Clean up thoroughly behind the seals. Bleed them through with fresh good quality fluid.

If you use a m/c with a smaller bore (ignoring levers for now) you will likely land up with more lever travel and more feel. A larger bore m/c will give less lever travel but also less feel. Quite easy to land up with the brakes feeling very dead.

All the best

Keith
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Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

Thanks Kickstart. I would renew my MC and caliper if I could find the parts for it. That's the biggest problem with this bike, no one lists it anywhere. I have to try and match stuff to other bikes. I will have a look around and see if I can find the renew kits. Bat motorcycles said they can order me any parts I need but then I'm paying loads for the stuff. Will phone them up in a bit.
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The caliper is a twin pot sliding caliper I think. Looks a similar design to the one on the 600 Divvy. Some Yamaha dealers are fairly helpful with stuff for Japanese imports (I have had good experiences with Granby Motors in Ilkeston for Japanese spec parts for my TZR250).

Yamaha are pretty good at not changing things for the sake of it, so plenty of parts are shared between different models.

All the best

Keith
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Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

Yes its a twin pot sliding caliper. It shares the same pads with the 600 Diversion so would that mean the caliper is the same?

Will try Granby Motors out. Thanks again Keith.
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

If its a kit for a Divvy I can probably get that from a shop by me and if its wrong they will usually change it over so will try that for the caliper. Now to try and identify the MC.

I have emailed Granby Motors so will see what they say.
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

I would ring them. Think they get a lot of spam so emails are fairly low priority for them.

All the best

Keith
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Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

I went to a local bike shop (B&J bikes, absolutely brilliant but don't expect an answer on the phone for a while. If your close its better to pop in) and they managed to find a master cylinder renewal kit for about £30 genuine Yamaha. New pistons and seals for the front caliper is £51 genuine Yamaha.

I could get it cheaper if I take it apart and they can match the parts but then I may have to wait a while and I won't have any transport until I get the parts and get it back together.

I'm probably going to get braided lines while the fluid is drained. I asked about a new front disc but its not listed and he doesn't have a price for genuine so I can take it off and they will check the dimensions and see what they can match it to.

Thanks
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Personally think braided hoses are over rated. That said you can pick up a single line braided hose with bolts for about £10 +postage.

The disk on the FZX looks very familiar. Not sure what from (possibly the TZR125R) but suspect that it will be easy enough to source.

All the best

Keith
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Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

I presume the caliper banjo bolt is the same as a Divvy? Is there anyway to find out what the master cylinder bolt is without taking it off?

Is it stinkwheel who sells them on here? Anyone know of some cheap places?
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The Divvy caliper looks like it is the same design, but think it goes on other fork leg.

There are pretty much only 2 different sizes of banjo bolt used on Japanese / European bikes. Same size but different thread pitch. Sickpup should be able to supply them.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

Carl Howell · Scooby Slapper Joined: 27 May 2008 Karma :

PM'd Sickpup but not got a reply yet.

Ordered the piston and seals and MC repair kit today. £83 in total.

Any tips for the MC as I haven't got a proper manual for it and never done it before.
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Owned: 2002 Gilera DNA 50, Yamaha DT125R

Own: Yamaha FZX250 Zeal (FZR250 engine as a similar shape to a Hornet)

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Watch out for your eyes and have some half decent circlip pliers. When yo take the m/c off and remove the lever you will find a rubber boot. Under this you should find a circlip that holds the piston in place. The piston has a spring the other side of it. You need to push the piston down an remove the circlip, then gently release the piston. Make VERY certain you which way the seals go (they are directional) when you reassemble it.

All the best

Keith
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