FXR brakes?

[John_H]

Thought I would start a new thread so that I don't take the bucket stuff wanted thread in the wrong direction.

Last race day I lost all pressure in my front brake, we bled them through and got a load of air out and all was fine. I went to the track today and the same happened but I couldn't re-pressurize the system. What would this be? Is it a stuffed master cylinder?

I don't really much about this sort of stuff so be slow with me!

[John_H]

If it does need to be changed, would one of these be good?

http://www.trademe.co.nz/motors/motorbikes/parts-for-sale/brakes/auction-649370200.htm

http://www.trademe.co.nz/Browse/Listing.aspx?id=648086114

http://www.motorbikeparts.co.nz/product_details.php?category_id=2&sub_category_id=24&product_id=861

Would I need a new line on any of these over the standard setup?

[Asher]

Could be the master cylinder.
Double check all the banjo bolts and any other fittings, although if it was getting air in anywhere else you would likely have fluid leaking out too (i think).

If you are going to replace it make sure you get the same size M/C

[Pumba]

I hate brakes and master cylinders. I have had a horrible set up for ages after toasting my good master cyclinder at one of the Road Race spectaculars when I decided to put the bike upside down. I have just put on one of Berts master cylinders (www.gprnz.com) and it has been great. More feel on the brakes than I have had for years.

Anyway I digress. It sounds like to me your master cylinder is rooted. You can buy a rebuild kit (I have never had much luck rebuilding them) or replace the cylinder altogether. I would not wast my time with the first one you posted as it looks a little small. Either of the second two should work well.

The key with master cylinders is to get the correct diameter bore (now I always get this bit wrong so wait for a qualifying statement for someone else). If it is two small you will not move enough fluid with each lever pull to activate the brakes (soft brakes), too large a diameter and you end up with minimal leaver travel and very little feel (wooden brakes).

I cant remember off the top of my head what the correct diameter is, but bigger is definitely not always better.

[Yow Ling]

FXR master cylinder is 11mm same as RG150

[John_H]

Bled the brakes again and managed to get the pressure up again. I opened the bleed valve and clamped the line and the lever was rock hard, so I am guessing it is not the master cylinder. No matter how much I bleed the brakes there still seems to be small bubbles coming through. Where will the air be getting in?

I did install a new braided line not long ago and I have checked that the bolts to the banjos are tight.

[Henk]

Most likely place is probably past the seals in the caliper if it gunged up or rusty. I've had issues in the past when the pads got worn down too far.

[John_H]

Most likely place is probably past the seals in the caliper if it gunged up or rusty. I've had issues in the past when the pads got worn down too far.

Thanks. What should I do about that?

[Tazz]

Thanks. What should I do about that?

Get a caliper kit for your bike, clean up the piston and replace the seals. Might as well do the pads while you're at it if they are low.

[Bert]

I hate brakes and master cylinders. I have had a horrible set up for ages after toasting my good master cyclinder at one of the Road Race spectaculars when I decided to put the bike upside down. I have just put on one of Berts master cylinders (www.gprnz.com) and it has been great. More feel on the brakes than I have had for years.

Anyway I digress. It sounds like to me your master cylinder is rooted. You can buy a rebuild kit (I have never had much luck rebuilding them) or replace the cylinder altogether. I would not wast my time with the first one you posted as it looks a little small. Either of the second two should work well.

The key with master cylinders is to get the correct diameter bore (now I always get this bit wrong so wait for a qualifying statement for someone else). If it is two small you will not move enough fluid with each lever pull to activate the brakes (soft brakes), too large a diameter and you end up with minimal leaver travel and very little feel (wooden brakes).

I cant remember off the top of my head what the correct diameter is, but bigger is definitely not always better.

We have had the best luck with the 12.7mm master cylinder with these size calipers. Currently awaiting new spring order.

If I was to pick any of the three I'd go with the third. I had a few issue with ones similar to the golden unit popping the feed tube under pressure (no circlip, just o-ring push fit).

So here's my normal bleed suggestions (I know Henk will add his).
Push the pads back in again and Pump them out again.
If that fails pressurise the system and crack the top banjo to check for air.
Check that all the pistons are actually moving.
Fails, push the pistons back in again and pump fluid in from the bottom up (100mm seringe works a treat). Much easier with a top bleed nipple.

You might be suffering from a poor seal on your new line/banjo is there any sign of leaking? Did your replace the washers?
I perdocally replace my copper washers with nice fresh annealed washers (have used alloy washers, but like copper, stay way from steel washers you will never get a good seal).

Part2.
Some lines have only one install direction (slightly different sides on the banjo: one to seal on the bolt the other against the mastercylinder or caliper.) if these are around the other way it's a shit to bleed. This gets compounded by some of the titanium banjo bolts on offer, they don't have enough space to use washers to get good seals.

Brakes....

[Pumba]

On that note, where the hell can you get copper washers now days. Tried a couple of the local engineering shops last time I need them but they had nothing small enough. Ended up getting some Ali ones from the local Yamaha dealer.

I too prefer the copper ones. You just get a better bite into them.

[Bert]

On that note, where the hell can you get copper washers now days. Tried a couple of the local engineering shops last time I need them but they had nothing small enough. Ended up getting some Ali ones from the local Yamaha dealer.

I too prefer the copper ones. You just get a better bite into them.

Occasionily I've seen them at supercheap. Copper is still used in the electrical world and I've found odd ball stuff like this at stewards electrical etc (trick is to keep it in the back of your mind for when you stumble on them; as you will never find them when you want them)...

[Kickaha]

On that note, where the hell can you get copper washers now days.
Brake shop, where else would you expect to find them?

[Grumph]

Brake shop, where else would you expect to find them?

Very true - speedway and motor racing supply shops will generally carry them too. If you can see an Earls/Aeroquip/Goodridge sticker somewhere in the shop, they should have them. Technically speaking, you're asking for crush washers.

[F5 Dave]

Actually timely. The Roti wrap shop I decided on for lunch is opposite Contour brakes here in the Hutt (Waterloo station). ok they charged me $10 for 10, but they are the right ones & his time counting them out must have been worth that. Now just got to put them where I'm likely to find them. Maybe 2 bags of 5 to double my chances.

Lamb Curry Roti wrap. Gotta try one.

[Tard]

I've had issues in the past when the pads got worn down too far.

Definitely I second that possibility. When I was topping back up with oil, initially pistons were travelling too far and you're just about guaranteed to end up with air bubbles trapped in the calliper. I rotated calliper 720 degrees and still had bubbles until finally figuring out pads were way past their best :weird:

[jasonu]

Brake shop, where else would you expect to find them?

EBay perhaps.