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Front brakes.

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Graeme77:
I had to take the lines of my front brake. After i re-fitted and bled it, it felt crap. Could get the lever all the way back to the bar. Dont know what they were like before though, never ridden it and didnt notice.

Found one of the hoses had a split outer so ive ordered new ones from hel.

Took the caliper apart and it was all a bit stuck, after cleaning it all up i found the piston is very poor. Very corroded right where the seal would be.

Are there any new replacements? Its an F1 and has a bigger piston, 42.8mm or there abouts.

I have another caliper but it has a smaller piston. Its not great either, but if this is also 750 i might be able to get a new piston. Is this my only option, or are the bigger ones available?

I might see if the engineers in work could turn me up a new one from stainless (i assume aluminium is no good?) as a last resort.

Also, thinking about the master cylinder. Is there any way to check this? I want to get all the parts ready so i can re-fit everything in one go at the weekend.
Could the master cylinder seals be why the lever felt soft and could come back to the bars?

Could i test it by putting a solid bolt in the outlet and see how it feels? I guess it sould be nice and solid, if not, theres a problem?

Spitfire:
The front brake piston on the F1 is no longer available, I replaced mine with a stainless one from eBay US, however there are others about,
here's discussion on the subject from a while back
http://www.sohc.co.uk/index.php?topic=2792.0
Here's more
http://www.sohc.co.uk/index.php?topic=2308.0
More
http://forums.sohc4.net/index.php?topic=23037.msg244590#msg244590

Cheers

Den

Grizzly:
This caliper was only fitted to the K7, K8, F1 and the automatic. The calipers fitted to the 550's and 400 four are the same style but are smaller. They were rubbish when new and 30yrs of use won't have helped. Good used calipers are like hens teeth. This might have something to do with the fact that they aren't sided and a lot of people have decided that a double disc conversion is a great idea ::)

I believe you can still get the master cylinder repair kits. But be aware that the bores inside the cylinders wear, which means no amount of bleeding and/or repair kits will fix that.

Keep checking Silvers. a while back he had a few new calipers for the automatic in stock, people twigged (different part no same part) and they went quick.

Using a stainless piston is fine.

My brakes were a real bitch to sort out. Read 4 calipers and 3 mast cyls. You would have to be dead unlucky to have the same problems as me. keep at it, it will come good in the end ;)

david451:

--- Quote from: Graeme77 on July 05, 2011, 06:50:13 PM ---I had to take the lines of my front brake. After i re-fitted and bled it, it felt crap. Could get the lever all the way back to the bar. Dont know what they were like before though, never ridden it and didnt notice.

Found one of the hoses had a split outer so ive ordered new ones from hel.

Took the caliper apart and it was all a bit stuck, after cleaning it all up i found the piston is very poor. Very corroded right where the seal would be.

Are there any new replacements? Its an F1 and has a bigger piston, 42.8mm or there abouts.

I have another caliper but it has a smaller piston. Its not great either, but if this is also 750 i might be able to get a new piston. Is this my only option, or are the bigger ones available?

I might see if the engineers in work could turn me up a new one from stainless (i assume aluminium is no good?) as a last resort.

Also, thinking about the master cylinder. Is there any way to check this? I want to get all the parts ready so i can re-fit everything in one go at the weekend.
Could the master cylinder seals be why the lever felt soft and could come back to the bars?

Could i test it by putting a solid bolt in the outlet and see how it feels? I guess it sould be nice and solid, if not, theres a problem?

--- End quote ---

If you clamp the flexi pipe then that eliminates the caliper and the lever should be solid.

There's two ways to bleed brakes the one where you open and close the bleeder as you pump, and that's shit. The best way to do it is to pump the lever 5-6 times, hold it back, release the bleeder and close it once the pressure has released, just a second. Keep doing that until you get a good brake, and no air.

kaceyk2:
Sometimes I am astounded by learning something new.
Thought I would share this with you.
My rally car building and driver neighbour showed me a magic trick to bleed bike brakes.
Take the claiper off the fork leg, and put a piece of wood inbetween the pads.
Get it held up in the air HIGHER than the master cyclinder on the handlebars.
Then do the bleeding, the air bubbles will now rise to where you want them to rise too....... The bleed nipple!
This really works well.

Tip no. TWo:  Use silicone brake fluid, it will polish chrome and paint work instead of wrecking and stripping it, well worth the extra couple of quid. It's purple, and goes in er, (sweary word coming up avert your eyes)
harleys.
there said it, but I did use a lower case h.

Hope this helps.

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