SF2 Front Brake Problem

CLEMTOG said:
"I assume that each bleed nipple has an integral ball that only allows a flow one way"
very sorry (and brutal) but have to say this state,ent by you shows a lack of general hydraulic motorcycle brake systems, I apologise again becaise I want you to gain knowledge on this, Hamish is absoluetly right the bleed nipple is just a taper end bolt with a hole to atmosphere above the tapered end which is its seat/seal.

iiS John is very likely right, strip the master cylinder to its bare bones, use brake cleaner and an air line to clear that tiny (of the two) holes of clag, which you have very likley missed, I use gas welders nozzles and a strand or two plucked from a wire brush, this will mean fitting (another) seal/piston kit to the master, since it is held in place by a crush washer which is not re-usable, to get the gubbins out. remove the hydrauluic hose union to reveal a female thread in the body, remove lever (obvious) and then, holding it gently in a vice (avoid crushing the cylinder) use a long pin punch to drive the kit out, no doubt as Points Marx previously advised you. Having two people on hand to bleed is helpfull, in, in, out, out, in, in, out, out. should be heard as the lever is pulled in the nipple is open, as the lever is let out the nipple is closed.
CLEM
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Hi Clem - FYI, I am a qualified Elec/Mech Engineer with over 60 years of varying experience. I am 82 years of age and still enjoying a lifetime of bike riding.
I should have checked the nipple spec but it seemed to me that a one way ball valve sounded logical but hey, what do I know!
I ask questions on this Forum not to show my ignorance but to gain specific knowledge from owners/riders who have "been there done that". It saves me a lot of time and money. This forum is particularly excellent at responding to my dumb questions.
One question - when I open each nipple valve, fluid comes through the the valve threads and not the aperture. Should the threads be sealed in some way?

Stay Upright!
 
Thread about a similar issue:-

Bleeding Brakes

I have completely overhauled the front Brembo brakes on my 750 SF1, replaced seals etc. Now trying to bleed the brakes but the fluid comes from the bleeder nipple threads rather than the nipple outlet. A forum member suggested using teflon tape around the threads. Is this required? Could be the...
laverdaforum.com laverdaforum.com

(Edit - Oops, sorry, just realised it was your thread previously, my bad.)
 
Bikepirate said:
One question - when I open each nipple valve, fluid comes through the the valve threads and not the aperture. Should the threads be sealed in some way?
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If fluid is not coming out of the bleed valve, but instead is coming from around the threads, then the valves are blocked. Remove them and poke a wire through them until you can see through them, then rebleed the entire system. A blocked bleed nipple will not allow air to escape, defeating the purpose of bleeding!
 
Alzero is correct, remove the bleed nipples and clear the air holes witha wire, but on re-assembly, put a dab of copper slip on the male thread, this will give yo a temprary seal on the thread, no matter what method of bleeding you choose, and the copper slip will prevent the thread seizing and you wont ever snap the top off (common)
CLEM
ps my favoured method is a hand pumped vacuum bleeder.
pps Moto V I have boxes of those one way bleed nipples, I thought they would be popular amongst Laverda triple owners especially those with a rrar disc, but alas they were not, I imported them from USA (via a visting relative) more as a service to club members than for profit, but that didnt work.
CLEM
 
I have a set of Russel Speed Bleeders, one-way bleed nipples, that I bought years ago for my Pantah and have been sitting in my spares draw for at least a decade. I liked their idea but just never got to fit them. The link is in post 20 of this thread.
 
Here is a pic, put in the ad cos I don't have a pic myself. They are just a screw with a hole through.
On my old callipers the base cone where the nipple seals is poxy so I have allen screws with ball bearings under and just let it make a mess when I bleed, and wash it off. I usually strip and clean the callipers instead of just bleeding off some fluid anyway.
 
Paul Marx said:
There is the old trick of leaving the lever pulled overnight with a bit of inner tube.
In the morning, it's bled.
The bubbles work their way up progressively and slowly.
No acrobatics.
Paul
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Hi Paul,

Still no joy I'm afraid. I still think it could be the master cylinder, so I've purchased a new Brembo kit 110-2739-20.
A quick question if I may. I am using the very useful Repair Guide by Laverdalothar for the dismantling/assembly of the kit. The master cylinder he illustrates is the one with the removable fluid reservoir. Mine is the solid cast alloy type (which I have assumed preceded the removable reservoir type). My question is, does my unit still use the above replacement kit?

Also, the instruction sheet that came with the kit only describes reassembly of the back brake master cylinder. All very confusing!

Cheers
 
The kit should be the same for both the solid and the plastic reservoir type. Assembly is basically the same for rear and front mc. The only bit I find tricky is how far to push in the outer seal, it isn't easy to feel when it is home. For info, I never get the solid mc to have as good positive feel as the later plastic one, from new the plastic ones felt much better, despite supposedly being identical internally.
 
Bikepirate said:
Hi Paul,

Still no joy I'm afraid. I still think it could be the master cylinder, so I've purchased a new Brembo kit 110-2739-20.
A quick question if I may. I am using the very useful Repair Guide by Laverdalothar for the dismantling/assembly of the kit. The master cylinder he illustrates is the one with the removable fluid reservoir. Mine is the solid cast alloy type (which I have assumed preceded the removable reservoir type). My question is, does my unit still use the above replacement kit?

Also, the instruction sheet that came with the kit only describes reassembly of the back brake master cylinder. All very confusing!

Cheers
Click to expand...
I believe the kit is identical. PS 15 front.
Paul
 
First post you said you'd replaced the complete mechanism in the m/c - and now you're fitting a new kit. This sounds like the same thing?

I strongly suspect you have air trapped in the splitter on the bottom yoke. Unbolt it, tilt it and give it a tap to dislodge air bubbles when bleeding.

It's also vital to angle the m/c uphill (lever end at highest point) to ensure air doesn't get trapped at the banjo. Mounted on the handlebar can result in that being the highest point.

Did you check the tiny hole in the m/c reservoir is clear?
 
Rob said:
First post you said you'd replaced the complete mechanism in the m/c - and now you're fitting a new kit. This sounds like the same thing?

I strongly suspect you have air trapped in the splitter on the bottom yoke. Unbolt it, tilt it and give it a tap to dislodge air bubbles when bleeding.

It's also vital to angle the m/c uphill (lever end at highest point) to ensure air doesn't get trapped at the banjo. Mounted on the handlebar can result in that being the highest point.

Did you check the tiny hole in the m/c reservoir is clear?
Click to expand...
The master cylinder kit I used previously was a spare kit which came with bike many years ago. I am suspecting that the seals could be suspect. Did all the rest of all the suggestions including the banjo and tiny holes. I intend installing the new kit, bleed as much as I can and then use a borrowed vacuum bleeder to finalise. Wish me luck!
Rob, thanks for the other suggestions. Rest assured everything that can be done will be done!
 
You'll all be pleased to know I have cracked it! The front brakes work fine now, thanks to the replacement master cylinder kit, a mates power vacuum kit and, of course, all your advice and assistance. These Brembo's certainly take a concerted effort to expel all the air out of the system. It looks as though I might have a similar problem with my 1200 triple but I feel a lot more confident of fixing it though!
 
It's always a surprise to me how some brake systems require a great deal of effort to bleed. The rear Yamaha Brembo and Duck Monster caliper setup on my bike was a proverbial PITA. In the end I had to virtually force fluid into the cylinder to get enough liquid to allow the pump to actually start (very slowly to move anything through to the caliper). It just wasn't getting into the guts via gravity. The front was a breeze.
 
piranha-bro2 said:
It's always a surprise to me how some brake systems require a great deal of effort to bleed. The rear Yamaha Brembo and Duck Monster caliper setup on my bike was a proverbial PITA. In the end I had to virtually force fluid into the cylinder to get enough liquid to allow the pump to actually start (very slowly to move anything through to the caliper). It just wasn't getting into the guts via gravity. The front was a breeze.
Click to expand...
My rear a pain too. Ended up having to flip it upside down to bleed the sucker.
 
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