bleeding master cylinder

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jeffmy

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Does the bleed valve on the caliper of a 72 Commando have an internal passage? I know the manual says to turn the valve out one full turn , put a hose on it and bleed the air out. I'm not getting any out the hose, just fluid out around the threads. So I' not sure if its getting bled properly. Any insight would be greatly appreciated.

Thanks,

Jeff
 
jeffmy said:
Does the bleed valve on the caliper of a 72 Commando have an internal passage? I know the manual says to turn the valve out one full turn , put a hose on it and bleed the air out. I'm not getting any out the hose, just fluid out around the threads. So I' not sure if its getting bled properly. Any insight would be greatly appreciated.
Click to expand...

The drilling in the bleed nipple is probably blocked.
 
Take the bleeder all the way out and clean the crud out with some compressed air or brake cleaner.


Tim_S
 
I find a touch over a 1/4 turn is enough to work bleeding issues.

And if you are getting bubbles around the bleeder screw, it might be that it is also letting air back in while bleeding. I would suggest you use a bit of heavy grease around the nipple - but not down in the threads when you put the old cleaned out (or new) bleeder back in. Just put the grease around the top - just enough to make it difficult for air to get pulled into the bleeder threads.
 
When I replaced my master cylinder I had to use a vacume pump. Even using that it took me FIREVER to finally bleed it.
 
I have found that a battery vent rubber hose fits nicely around the bleeder. It shouldn't take more than 15 minutes usually to bleed that norton brake if you have an air tight system. That includes clean-up....



Tim_S
 
I use a power bleeder on all brake systems, now. It requires a modified reservoir cover to attach a nipple to. An ordinary, small capacity weed sprayer does the job. Some have reported good results with reverse power bleeding. Makes sense to push the air up rather than down.
 
"reverse power bleeding" ? is that forcing the fluid down? up? vacuum up? down? not sure what you mean there
 
Thanks for all the replies, I'm definitely going to try a few and report back.

Jeff
 
Reverse power bleeding is forcing brake fluid from the bleed nipple on the caliper to the master cylinder reservoir. Power bleeding is forcing fluid from the master cylinder reservoir to the caliper.
 
so obviously with reverse power bleeding, no lever action can take place. and with power bleeding??
I've never had to do any of these . I'm just lucky.
 
Only thing I know is Combats and never had a air bleed issue on a dozen times doing this. Normal automotive method of squirt out of bleeder a few times, closing bleeder before lever release, then top off master cylinder and very carefully work lever till the big bubbles quit and then some more - more careful levering to expel as much the foam size bubbles till bored, then go ride carefully a while to finish air out or strap lever open over night with bars turned to elevate area better all the time keeping in mind the tank paint protection. Just did this couple days ago after resealing the lever boot leak that turned out to be fractured retaining washer. Got carried away to jet fluid on tank but its waxed and I had dry cloth ready to get it off fast. I did not have to strap level back this time as didn't fully drain system but a bit below m/c so hose didn't have to ever so slowly give up its adhering air layer.
 
I never had to power bleed my Norton yet, but my BMW K75 and four wheelers needed no master cylinder actuation, either lever or pedal. In fact, power bleeding is the only way the ABS on my K75 will work.
 
I got the bleed valve cleaned out (a lot of gunk in there)bled the m.c. several times, til I was sure no more air.Using Dot 5 fluid by the way. And this is the stock m.c., took it out for a spin and the brake action is not very good, this is after rebuilding m.c. and adding a new braided s.s. brake hose.Would new brake pads help and am I going to have to go to the much talked about 13 mm upgrade ?

Thanks for all the advice,

Jeff
 
Jeff,

There are numerous threads here that lament the poor braking of a stock setup. It just won't stop the motorcycle very well. It's all about the size of the master cylinder. It's too big. Period! You currently have a 5/8" master cylinder.

Check this out: http://www.vintagebrake.com/mastercylinder.htm
 
Diablouph said:
Jeffmy, just go and try a bike with a 13mm upgrade. I bet you will have one ordered that day.
Click to expand...


Indeed! That will make a believer out of you.

If you willing to spend more money than a resleeved master cylinder costs, I'd recommend changing out the rotor to a 12" floater with a decent 2 piston caliper, such as the Brembo or Lockheed racing or Grimeca caliper and couple this with a 11 mm master cylinder and you'll have a stopper that performs on par with a lot of the dual disc setups.
 
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