1998 Rear Brake

I have 1998 VFR 800 it has been off the road for a while. I am currently flushing the brake fluid & replacing.
I have noticed that the center rear piston is not releasing. I have a question relating to the Linked Brakes.
When the bike is stationary and you press the rear brake lever should the center rear piston move?

 

I'm pretty sure that the center piston is operated by the front secondary master cylinder, so no, it won't move when you use the rear brake lever. You have to depress the secondary master cylinder to move the center piston.

I'm sure someone will correct me if I'm wrong, but I don't believe I am. I could go down and look at the schematic, but I'm just too lazy. LOL

 

The center piston is actuated by the secondary master cylinder in the front forks that is compressed when the front brakes are applied and the left (or right? Bikes not in front of me) front caliper grabs the rotor and pushes up against it.

Shorthand no... Haha


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Thank you for that.
Therefore if the center rear piston moves when I press the rear brake lever, The secondary Master Cylinder must be stuck open.

Also If the above is correct how can you Bleed the rear Centre Piston without a Vacuum bleeder?

 

The center rear piston will not move when you press the rear brake lever because there is no circuit directly connecting the two.

If the center piston is sticking, the PCV could be gummed up and not allowing the brake fluid to release the pressure.

It's hard to explain how to bleed the brakes, they are pretty complicated. It's not horribly hard to do, but difficult to explain.

 

I believe that vfr discussion has manuals that explain the bleed procedure, I haven't had to do it yet, so I am not positive on how to bleed then correctly. If the center piston moves when you push the rear pedal and it is connected to the front, I'm not sure what to tell ya.



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Again Thanks for your advice
I have bleed the brakes now at least three times. I am following the Honda Manual procedure. I can achieve a "good" peddle and Lever. When I re check all bleed nipples I get a good stream of fluid with no air bubles.
But I do not understand how pressing the rear brake peddle operates the center rear piston. My understanding is as yours, this piston is operated by the LHS caliper rotating and actuating the secondary master cylinder which will pressurize the PCV valve then when this cracks fluid will flow to the center rear piston.
I can see if the PCV valve is "gummed" up. There seems to be no info on stripping this valve that I can find, This may explain why the fluid is not returning. But does not explain why the piston is moving with the rear brake lever.

 

Are all 3 Pistons moving with the rear pedal?


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Yes they are. The two outer ones will release tension when you release the rear brake lever. The center one will stay pressurized. I can release the pressure by un-doing the bleed nipple.
There fore I suspect that the secondary master cylinder is at fault. As I understand that when you press the rear brake lever the two rear outer pistons will move the LHS Front Middle piston, then the Delay valve on RHS front Leg will crack and bring in the RHS Middle front piston, As the supply for the secondary master cylinder is from the rear circuit and joined with the LHS Front Middle piston. I have replaced the seals, Piston Spring and boot for the secondary master cylinder. I am open to any logical comments to help me solve this problem.

 

I am having the same issue with a three pistons moving with the rear brake lever. I have orderd and replaced the SMC piston set which did not fix the issue. I have been reading that there is some type of valve behind the SMC's feed line banjo. It does not look like you can order this part so I have purchased a left front caliper off of ebay to find this part. When I get this completed I will let you know how it goes.

 

The proportional control valve perhaps? It's under the seat, to the rhs of the rear of the fuel tank and can be bled fairly simply. I hope this photo shows ok...

 

If you save the photo and open it using a viewer you ought to be able to read the text too. Instructions here:



Hope this helps.

 

If you save the photo and open it using a viewer you ought to be able to read the text too. Instructions here:

View attachment 31719

Hope this helps.

--edit--

Looks like the photo uploader won't allow high enough quality to be able to read it. Sorry :unsure: