Bleeding Proportioning Valve

[SpikingJC]

I'm in the process of bleeding all the brakes and I seemed to have problem with the proportioning valve. I did tilt the SMC 15 degrees as stated in the SM. When the vacuum hose is attached to the valve, it doesn't seem to pull any fluids through. It felt like the hose to the proportioning valve is clogged.

I went ahead and bled all the other valves and although the brake level and pedal felt a bit mushy, I do have some brakes. However, when I pull the front brake level, it does not apply any braking to the rear at all.

Any suggestion on how to clear that up?

Thanks

 

[sky.high]

I don't know much about the actual bleeding process but do know the rear brake is activated by the turning motion of the fornt wheel and has no effect when the brakes aare applied and the bike is not moving.

 

[SpikingJC]

Yeah, I realized that when I was driving to get some lunch. I guess an empty stomach does affect the brain...

Still wonder about bleeding the proportional valve though....

 

[Tom Mac 04a]

Still wonder about bleeding the proportional valve though....

it tends to come out very slow from here.... help it along by pumping also speeds it up alot

 

[dduelin]

If you pump the brake pedal you'll bleed the PCV with no problem. That's a long circuit, the longest in the system. Rear master cylinder thru the PVC thru the SMC then back to the rear caliper. The MityVac needs help. I pump 10 or 12 strokes of the brake pedal then check the fluid level in the rear reservoir. You must redo the entire procedure now because you left air in this circuit.

As it was posted above - the front wheel has to be turning in a forward motion to impart rear brake action from the front lever. There is no direct plumbed circuit from the front lever to the rear caliper. The action of front brake moves the hinged left front caliper forward and this presses the pushrod against the SMC and forces fluid to the rear caliper.

 

[Anna'sDad]

There is no direct plumbed circuit from the front lever to the rear caliper.

Indeed, here's a schematic of the brake system, perhaps a bit of visualization will help.

 

[okmurdog]

I pump both the SMC and the rear brake when bleeding the PCV - works great and also exercises the SMC...no problems.

 

[SpikingJC]

Thanks everyone. Pumping the brake pedal does help a lot in getting the fluids through. Once most of the air were bled, it got easier to do. After going through all the other valves, the brake feels much better.

One last thing. Whenever I bled any of the fluids from the rear MC, the front brake level seems to loose all pressure. I have to pump it a couple of times to get the pressure back. Can anyone tell me why? Is there something I'm not doing it right?

JC

 

[okmurdog]

Sounds like there is air in the front brake circuit. If it were me, I would re-bleed the front brakes. If you use the vacuum method, double check to make sure air is not being pulled thru the threads of the bleeder valve(s) on the wheel cylinders.

 

[treemuncher]

Be sure to put teflon tape on all of your bleed screws. Otherwise, you may be sucking a lot of air.

Do a conventional bleed mixed with the vacuum pump method. Apply vacuum to desired bleeder, pump your brakes and hold pressure, then crack the bleeder open to expel air, close bleeder, release brake pedal/handle, pump up to build pressure with pedal/handle again and repeat sequence until only clear fluid without any bubbles coming out.

DO NOT allow your MC reservoirs to go dry or you will have to start from scratch.

I use a wood or plastic wedge to hold the tupperwear back on the right side after removing the top and front screws to access the PCV without completely removing everything. Works great with a 90 degree fitting on the end of the vacuum pump hose. If you do not bleed this valve, your rear brakes will hang up and burn.

 

[SpikingJC]

Be sure to put teflon tape on all of your bleed screws. Otherwise, you may be sucking a lot of air.

Do a conventional bleed mixed with the vacuum pump method. Apply vacuum to desired bleeder, pump your brakes and hold pressure, then crack the bleeder open to expel air, close bleeder, release brake pedal/handle, pump up to build pressure with pedal/handle again and repeat sequence until only clear fluid without any bubbles coming out.

DO NOT allow your MC reservoirs to go dry or you will have to start from scratch.

I use a wood or plastic wedge to hold the tupperwear back on the right side after removing the top and front screws to access the PCV without completely removing everything. Works great with a 90 degree fitting on the end of the vacuum pump hose. If you do not bleed this valve, your rear brakes will hang up and burn.

Thank you for that instruction. I guess I've been doing it wrong all these times.

 

[treemuncher]

I tried skipping the PCV and wound up with a rear caliper that would not release and burned the pads. What I posted is the way that works best for me after several tries. Be sure to follow the sequence listed in the repair manual. As a former auto mechanic, I find it hard to beat the old method of "pump & hold pressure". Adding the vacuum keeps it cleaner and ensures a good bleed.

I've had plenty of practice on my bike, Fali's bike and Tommy's bike in the past couple of years. I think that they are all rolling and stopping just fine after the bleeds.

I hope that you are able to get yours done without the numerous problems that I have encountered.

Be sure to check the SMC for proper operation prior to the bleed. Disassemble and clean it up if it sticks at all.

 

[SpikingJC]

I've been following the sequence exactly. The thing I'm having trouble is with several bleed valves where I just could not keep a perfect seal for vacuum. I've used teflon tape, but air just keeps leaking in. This makes it a complete guess whether all the air has been bled. It makes me think there may be issues with the valve itself, because I've use the same tube on several other valves, and they're completely sealed. I'll try to wrap more tape and give it a try again.

 

[SpikingJC]

After going through the entire bleeding sequence for like 10 times (actually, it was 4), I think I'm finally done. There were still a few valves where I could not get a perfect seal and I just pump a couple of MC full of fluid through them to hopefully blow all the air out. The last one was kind of strange. When I hooked up the vacuum tube, and pump up the vacuum, I was getting a good seal. As soon as I opened the valve, I was getting tons of air through it. Some bubbles were slow and tiny, some were as large as the opening of the valve. Even pumping ~5 MC full of fluid by using the brake pedal, air bubbles were still coming out. Mind you, this is the fourth time I'm bleeding this valve. At this point, I can only determine there are some problems with the valve itself and somehow air is getting pulled in through the thread of the valve.

So the bike it ridable. I'm getting good pressure both at the level and the pedal. While I was there, I adjusted the brake pedal height as well as the brake light switch at the pedal to make it more sensitive. Can't wait to take it out tomorrow after a month and a half of sitting in the garage.

On the plus side, I used the down time to install a Bestem T-Box and hooked up the LED in the box to my Hyperlites.

I just wanted to thank everyone for the helpful advice, without which the bike would still be in pieces.

JC

 

[dduelin]

I failed to mention it earlier but I don't use any of the MityVac hose end adapters. They don't seem to seal well or stay on the bleeders so I slipped a piece of 5/16" OD 3/16" ID vinyl hose into the end of the supplied hose and use that over the bleeders. It's a real tight fit. Of course the first time I bled the brakes I wrapped the bleeder threads with plumbers sealing tape and haven't had to do that again. Usually 1.5 to 2 master cylinders worth of new fluid is sufficient to bleed each circuit. Maybe it will go better next time.

 

[okmurdog]

Quite frankly, a Mityvac is not necessary to bleed the brakes. Many of us simply use a one-way check valve to bleed the brakes, and it works without any hassles. I chose to machine off the threads from a Speed-bleeder and place it inline with a hose pigtail to use as a check valve. Motion Pro also makes a check valve for brake bleeding.


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[SpikingJC]

Quite frankly, a Mityvac is not necessary to bleed the brakes. Many of us simply use a one-way check valve to bleed the brakes, and it works without any hassles. I chose to machine off the threads from a Speed-bleeder and place it inline with a hose pigtail to use as a check valve. Motion Pro also makes a check valve for brake bleeding.

I didn't even know there is such thing as a check valve for bleeding. Are you talking about something like this:

http://www.motionpro.com/motorcycle/partno/08-0143/

or this?

http://www.motionpro.com/motorcycle/partno/08-0482/

 

[okmurdog]

I didn't even know there is such thing as a check valve for bleeding. Are you talking about something like this:

http://www.motionpro.com/motorcycle/partno/08-0143/

or this?

http://www.motionpro.com/motorcycle/partno/08-0482/

I don't personally have any experience with the MP bleeders, although the one pictured in the first link looks like it would be suitable.

 

[Igofar]

:call:.......The ST Whisperer....

 

[Mick]

I didn't even know there is such thing as a check valve for bleeding. Are you talking about something like this:

http://www.motionpro.com/motorcycle/partno/08-0143/

That's the one you want. Works like a charm.

I'm sure others have had different experience but I tossed my mytivac in the corner many years ago shortly after buying it and haven't used it since. I found it useless. You can't go wrong with the Motion Pro tool. It allows you to bleed the brakes properly by yourself. Before I got the Motion Pro tool, I bled my brakes the old fashioned way with my wife operating the pedals & levers and me operating the bleed valves.