Triumphrat

Tbirdnz · 10-07-2009, 10:12 PM

Just changed the two pistons and seals in my TB's front brake calliper. Had the same trouble bleeding the system as when I had changed the master cylinder piston last year.

I've bled countless brakes of cars and quite a few bikes but for some reason on my TB when I lose total pressure it's extremely difficult to get it back. Tried for an hour the conventional way of bleeding and in the end resorted to sucking the air out with a bulb sucker and a plastic tube attached to the bleed screw (same tube I used for bleeding) and got sufficient pressure to then bleed normally. 5 minutes as opposed to no-hope the normal way ! I'd had to do it that way with the master cylinder too, don't know why I didn't do it straight away with the calliper !

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Ride on !

denny · 10-07-2009, 10:26 PM

I've had better luck filling the system by pumping the fluid in through the bleed screw. A Mighty Vac, or a large plastic syringe (available at a farm store in the animal medication section).

That seems to force more air out through the MC. Then after filling bleed in the normal way.

faffi · 10-08-2009, 04:09 AM

Try to tie the brake lever firmly against the throttle grip for 24 hours or more. Tap the brake caliper and banjos lightly every now and then to help those air bubbles rocket upwards. I went from no resistance to OK after 24 hours and after another day got a really firm lever without any bleeding work at all.

It is important that the point of the brake lever sits at the highest point, which means handlebars turned to the left.

buckoz · 10-08-2009, 06:10 AM

Quote:

Originally Posted by faffi

Try to tie the brake lever firmly against the throttle grip for 24 hours or more. Tap the brake caliper and banjos lightly every now and then to help those air bubbles rocket upwards. I went from no resistance to OK after 24 hours and after another day got a really firm lever without any bleeding work at all.

It is important that the point of the brake lever sits at the highest point, which means handlebars turned to the left.

+1 faffi works everytime and leave the filler cap just sitting on
tape the lever to the bar

Legend JJ · 10-08-2009, 10:58 AM

i had the same problem when i drained out my front brake and had to use a MightyVac to get pressure back in the line. i actually found it easier to bleed the cylinder down to minimum (without letting air get in!) and refill it till there's nothing but fresh fluid in the system. it only took 5 mins to do the rear brake this way. i'll just stick with that since i'm too lazy to build a clever syringe tool like ssevy made

Quote:

Originally Posted by ssevy

I use a catheter syringe, and it works better than my Mity Vac. One point I have mentioned in other brake threads is to wrap your bleeder threads with teflon plumber's tape. Every time you loosen the bleeder screw, air can get drawn back into the line through the gap in the threads, and you'll never get it all out. With the syringe, you can prefill it full with the new fluid and then attach the clear hose to the bleeder and simply push it into the line. To get rid of the old fluid first, you can either use the syringe as a resevoir to hold it as you pump the lever, or just open the bleeder and pull the syringe piston to draw it out. Works great, and you can see when the clean fluid has filled the system.

Old Fluid:

Clean Fluid:

Tbirdnz · 10-08-2009, 07:31 PM

It seems a good suggestion in the quote by Mienzio of the ssevy tip to wrap the bleed nipple thread in teflon plumber's tape as air can get into the bleed nipple threads when bleeding if you open them too much when trying to gain initial pressure. It only needs a small turn of the bleed nipple to let fluid escape. I have never used tape that way but you have to be careful not to allow air into the bleed nipple threads otherwise you are totally wasting your time.

If you pump fluid into the bleed nipple to fill the master reservoir then make sure the top cover is on without being tightened down and protect with a rag around it for leaks otherwise you will spray fluid out of the reservoir.

I've also tried the overnight method of tying the brake lever to the bar and tapping the brake line and calliper but it's a hit and miss method.

Definitely using suction or pumping the fluid in is the fastest and surest way of getting air out of the system when you've lost all pressure in my experience.

....and I'm going to get myself a ssevy syringe, it's better than the one I used.

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Ride on !

ssevy · 10-08-2009, 08:40 PM

Just to clarify - I have no financial interest in catheter syringes; I happened to find this one while cleaning out some of my deceased father-in-law's workbench inventory, and like him, I never throw away anything that might be useful someday. This spring when it was time to do the brakes, I remembered it and gave it a go. For those of you with healthy plumbing who don't have a catheter, I have seen similar syringes in small engine shops, where they sell them for measuring oil for premixing.
As for the teflon tape, it worked great for me. Just be careful when wrapping that the tape doesn't slip over the bleed screw opening. Keep it only on the threads, and don't overdo it. Also, wrap so that the tape overlaps itself in the correct direction when tightening.

Tbirdnz · 10-08-2009, 11:15 PM

I went out this morning to buy a syringe, and found out they are illegal to be sold in pharmacies ! Even when you explain you don't want the needles !

However farmers are allowed to buy them in Farm supplies companies, good sense prevails, so I bought one !

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Ride on !

denny · 10-08-2009, 11:18 PM

It takes a large dose for a Horse or Cow!

Tbirdnz · 10-08-2009, 11:24 PM

...what ? brake fluid !

I do have an injector gun for cattle (used for drenching) but I didn't want to contaminate it with brake fluid !

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Ride on !