Front Brake

brf1957 · Feb 28, 2010

Hi All , I have the standard lockheed master cylinder and caliper and rubber hose on my 73 850, i have renewed the seals on the caliper and master cylinder and fitted stainless pistons, have bleed the brake loads of times and still the first pull of the lever it comes nearly to the bar, second pull is fine is this normal with the commando brake as my mates interpol does the same or is there something else needing attension . as always thanks in advance for any replies Brian

maylar · Feb 28, 2010

Not normal. Bleed it again.

tpeever · Feb 28, 2010

I seem to have a harder time bleeding my Commando brake line compared to my other bikes. There always seems to be residual air in the line for a long time after I bleed it and it is hard to get it all out. A little trick I read somewhere that really seems to work is to bleed the line the best you can but then pull in the lever and bungee cord it to the handlebar. Leave it overnight and the remaining air bubbles will work their way up to the reservoir and out. Works great. I would also recommend a stainless line as this will increase braking power and looks really good too!!

brf1957 · Feb 28, 2010

thanks for advice will try that tonight ,should i leave master cylinder cap off or on to do this

pbmw · Feb 28, 2010

Mity Vac or a syringe works well.

JimC · Feb 28, 2010

The best way I've found to bleed motorcycle brakes is to power bleed them. I use a small pressurized weed sprayer hooked to a sacrificial master cylinder cap. I use a pint or so of fluid when I blast the system. Seems to get the job done and quickly. I found using a vacuum bleeder can still leave brakes somewhat spongy. In fact, on a BMW ABS system you have to power bleed.

Don Tovey · Feb 28, 2010

Hi BRF,
No need to leave the master cylinder cap or seal off when leaving the lever tied tight overnight .
When I bleed my system I give the lever lots of little light squeezes while the seal & cap are off & you can see little air bubbles coming to the surface.
I would also recommend getting the longer brake lever which gives you better leveridge & makes for better braking, & its somthing that dose not look out of place.
Best of luck.
Cheers Don

gtsun · Feb 28, 2010

My bike came with a master cylinder that had just been re-sleeved, the instructions said to use the syringe with a hose to "push" fluid from the bleed nipple up to the M/C. Any thoughts good or bad about doing this anyone???

cash · Feb 28, 2010

My bike came with a master cylinder that had just been re-sleeved, the instructions said to use the syringe with a hose to "push" fluid from the bleed nipple up to the M/C.

Nothing wrong with that and can help when the nomal way fails.

Cash

grandpaul · Feb 28, 2010

Gravity is a wonderful thing.

...so is a screwdriver handle!

With those two tools, I bleed out Lockheed systems to a very satisfactory level.

Do the usual system bleed, top off the reservoir, then start tapping the entire fluid-bearing system from bottom to top, while very gently pumping the lever the very first part of it's stroke (just enough to shift the orifices into the range of opening where the fluid starts to move, like Don said).

As you pump repeatedly, tap the screwdriver handle on the caliper, then the hard pipe connection then all the way up the brake hose, then the connection at the master cylinder. Go from top to bottom a couple of times. Typically this is all I ever need to do to get a solid lever.

MexicoMike · Feb 28, 2010

Just like a car, any sort of pressure bleed is the quickest and surest method. Whether it's from the caliper or the master cylinder doesn't matter. On a bike the syringe from the caliper is easier unless you already own a pressure bleeder kit that can fit on the masteryclinder.

B+Bogus · Mar 1, 2010

grandpaul said:
Gravity is a wonderful thing.

...so is a screwdriver handle!

With those two tools, I bleed out Lockheed systems to a very satisfactory level.

Do the usual system bleed, top off the reservoir, then start tapping the entire fluid-bearing system from bottom to top, while very gently pumping the lever the very first part of it's stroke (just enough to shift the orifices into the range of opening where the fluid starts to move, like Don said).

As you pump repeatedly, tap the screwdriver handle on the caliper, then the hard pipe connection then all the way up the brake hose, then the connection at the master cylinder. Go from top to bottom a couple of times. Typically this is all I ever need to do to get a solid lever.

I'm with GP on this, especially with old hoses. I never had to do this with new/recent model bikes or new hoses, so I my assumption is that any corrosion/age related contamination in the hose would hold air bubbles, hence preventing them being moved up and out with normal bleeding.
Rubber brake hoses have a finite service life too. Definitely good practice to replace (especially with braided hose - just hold the rubber pipe when you apply the brake to see (feel) what I mean).
I've also found that screwdriver useful for prising the pistons apart with the front wheel out, but a tyre lever is the best thing here - it just gives a bit more 'push'...just make sure the cap is placed loosely back on the reservoir as quite a geyser can be generated

.

Still recommend putting a braided hose on though!

Coco · Mar 1, 2010

gtsun said:
My bike came with a master cylinder that had just been re-sleeved, the instructions said to use the syringe with a hose to "push" fluid from the bleed nipple up to the M/C. Any thoughts good or bad about doing this anyone???

I've been doing it that way for years. You'll spend $10 at the veterinary supply store for a large syringe and some clear tubing.

I'll tap the lines and caliper to move all the air bubbles up, squeeze lever ect....