master cylinder

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jerryd
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Re: master cylinder

#16

Post by jerryd » Mon Nov 13, 2017 10:00 pm

It comes up through the small hole straight below the fill hole on top . If I push the piston in without the cap on it blows right out and adds to the mess if i don't put cap on
jerry



Doc37W
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Re: master cylinder

#17

Post by Doc37W » Mon Nov 13, 2017 11:15 pm

There should be a tiny hole above the piston and a larger one just in front of the rubber cup. When the fluid is forced back into the master cylinder, it will flow into the reservoir though the large hole. At no time should you try to push the piston past the tiny hole, & yes, any fluid trapped between the the o-ring on the piston and the rubber cup will be forced up & out, making a gyser of fluid! Push slowly! A soft pedal means you still have air in the lines. You may have to back-bleed the the system, by using an oil can full of brake fluid and a hose attached to the bleeder nipple on the rear brake cylinder, as PanPal suggested. Doc

jerryd
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Joined: Mon Jun 16, 2014 12:47 pm
Bikes: 58 FL, 74 Norton Commando, 70 T100R, 72 Yamaha 75, 65 Honda C65

Re: master cylinder

#18

Post by jerryd » Mon Nov 13, 2017 11:44 pm

Yes I appreciate that the piston should not be pushed in to far . It sitcks at 1/2 inch in and won't return . however I have to be away a few days so i will try reverse bleed with an oil can next weekend. I have already tried it with some large syringes I have . I will conquer this . Thanks for the help so far.
jerry

james
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1952 FL
Location: Wrightsville Pennsylvania

Re: master cylinder

#19

Post by james » Tue Nov 14, 2017 2:02 am

Don't forget if you have a nicely painted frame, backing plate etc.,brake fluid squirting out all over will ruin it.
Take precautions.
Jim M

RUBONE
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Re: master cylinder

#20

Post by RUBONE » Tue Nov 14, 2017 2:05 am

What fluid are you using? And what fluid are the internals rated for?

jerryd
Posts: 119
Joined: Mon Jun 16, 2014 12:47 pm
Bikes: 58 FL, 74 Norton Commando, 70 T100R, 72 Yamaha 75, 65 Honda C65

Re: master cylinder

#21

Post by jerryd » Tue Nov 14, 2017 4:03 am

I am using DOT 3. As Doc37w said earlier in a post a smooth cup can use either 3 or 5. Had the 3 on the shelf. I will get 5 if that would make a difference. I have this MC in the vise so most of the mess is there trying to figure why it sticks. Had some loss at bleeder screw only and cleaned up.
jerry

jerryd
Posts: 119
Joined: Mon Jun 16, 2014 12:47 pm
Bikes: 58 FL, 74 Norton Commando, 70 T100R, 72 Yamaha 75, 65 Honda C65

Re: master cylinder

#22

Post by jerryd » Sat Nov 18, 2017 2:30 am

got back into the shop again. I took apart the new cylinder again to be sure all is in order. Reassembled and used oil can method to bleed while in the vice. again the piston was sticking but slowly returned almost to the washer. another pump from the can and it returned. Ok into the bike. I back bled from wheel cylinder to the MC . I probably pushed most of a quart through. 10 pumps then remove some from MC with a syringe. I made sure no air was in the line before it was attached to the bleeder valve. The shoes are set to a slight drag on the drum. the drum is new and shoes arced to drum . The pedal moves the piston 1/2 to 5/8 inch before I have a brake. Piston bounces back a 1/4 inch and slooowly comes back almost to the washer. Won't know she stops til it is on the road. There are no leaks anywhere on the connections. Is this as good as it is going to get?
jerry

PanPal
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59 FLH running restoration
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Re: master cylinder

#23

Post by PanPal » Sat Nov 18, 2017 3:02 am

Youre getting there. You still have a air pocket. May be in the wheel cylinder now. Did you try bleeding normally after the oil can?

jerryd
Posts: 119
Joined: Mon Jun 16, 2014 12:47 pm
Bikes: 58 FL, 74 Norton Commando, 70 T100R, 72 Yamaha 75, 65 Honda C65

Re: master cylinder

#24

Post by jerryd » Sat Nov 18, 2017 2:32 pm

No I did not try the usual way , push , open , close release because the piston was staying in and so slowly releasing. And it was supper time. Hope to have a couple hours later today. You would think all that fluid pumped through would have dispelled any air. Broke my one big syringe I was using for vacuum bleeding so I will try to get another. Where would you suggest the air is trapped?. I went to school to be a mechanic 40 years ago but never got licensed. Stayed farming with dad. I worked in a school bus shop. and maintained as many as 5 vehicles in my own garage.. I have done many brake jobs but this simple system has me boggled as to why it won't bleed. Thanks for the help. will be back. jerry

Doc37W
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Joined: Wed Jul 29, 2015 4:56 pm
Bikes: '37 W,'41 ULH,'59 FLH Handshift,'69 Fl Handshift w/sidecar,

Re: master cylinder

#25

Post by Doc37W » Sat Nov 18, 2017 5:18 pm

I have used a wooden handled screwdriver as a small hammer (to avoid dents in the steel line) and tapped on the lines lightly (where I could get to them) all the way from one end to the other. The idea was to dislodge the air bubble and allow it to travel to the high point of the system (usually the master or slave cylinder). Then, I'd bleed the line. Also, just leaving it overnight will let the system to settle out the air. The piston should only move about 1/2" or the distance from the tiny bleed hole to the o-ring on the piston. Doc

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