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Discussion Starter #1
I was wondering if there is a way to push the front brake caliper pistons back into the caliper...


The PO of my '86 VN750 unhooked the front brake calipers from the rotors before storing the bike for twenty years. It looks like he then pulled the brake lever, effectively closing the brake pads on themselves.

My question is, what is a good way to get the pistons to release and slide back into the caliper housing so I can see if I have positive brake pressure?

I was thinking of taking two screwdrivers and inserting them gently under the lip of the piston and rotating them up, so the pistons slide back into the housing, thereby freeing up the front brake shoes...or is there a better way to do this? I certainly do not want to gouge the pistons, but I see no other way to get them to slide back into their calipers...any ideas would be great!

John
 

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I use a c-clamp and brake pad or a small piece of plywood. Then press them in nice and slow.
 

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Discussion Starter #3
I wound up taking off the banjo bolt and releasing the fluid in the calipers; I applied two screwdrivers very carefully under each side of the piston and leveraged them up - they then slid right up, so I'm thinking there's a blockage in the line somewhere. At least the pistons themselves are okay...

The hairy thing was, I Finally got the brake master cylinder piston washer/cover off, intending to take out the old parts and rebuild the master cylinder...the whole circular channel the parts rest in was solidified! The bike has sat for so long the entire inside of the master cylinder piston literally petrified inside it!

I tried digging it out - all that old, caked, chalk-like substance - but it's no good, the master cylinder is shot. As a matter of fact, the master cylinder piston itself broke off inside the master cylinder tube due to corrosion. I've never seen anything like it! It's toast.
 

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I wound up taking off the banjo bolt and releasing the fluid in the calipers; I applied two screwdrivers very carefully under each side of the piston and leveraged them up - they then slid right up, so I'm thinking there's a blockage in the line somewhere. At least the pistons themselves are okay...

The hairy thing was, I Finally got the brake master cylinder piston washer/cover off, intending to take out the old parts and rebuild the master cylinder...the whole circular channel the parts rest in was solidified! The bike has sat for so long the entire inside of the master cylinder piston literally petrified inside it!

I tried digging it out - all that old, caked, chalk-like substance - but it's no good, the master cylinder is shot. As a matter of fact, the master cylinder piston itself broke off inside the master cylinder tube due to corrosion. I've never seen anything like it! It's toast.
and it's also the most important part of your bike. i would imagine that 65% or more of the vn750's brake force is up front on that dual disc. it's one thing to have a bike that sputters and dies. it would be quite another to have massive front brake failure in an emergency situation. find a used one but make sure it is clean too, some of the ebay dorks don't even remove the cap and look. and yes i have seen the dried gunk you are talking about, quite a nasty horrible looking mess, and should be dropped right into the trash can. one of the members here might have one, check the classified ads. and good luck bleeding it once you get fixed, quite a pain! takes a long time to get all the air out!! i need to re-bleed mine once again! i'm going to try tie wrapping the lever and letting is sit for a day or two.
 

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I'm junking an old frame with the front wheel and the calipers are still attached and appear functional. If you want 'em let me know, will cost you whatever the postage is on the box.
 

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Discussion Starter #6
Yeah, I'm definitely interested! You don't happen to have the brake lines and master cylinder that attaches to them , do you? :)

What's your zip code?

PM me if you want; thanks!
 

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I used a little different method to bleed my front brake. I took a small jar with a good sealing lid, and drilled the lid and put two fittings in the top. I hooked one line from one fitting on the jar to my vaccum pump. I took another line and connected it to the other fitting on the jar and the other end I pushed it on my caliper bleeder screw. I turned on the vaccum pump and while keeping the master cylinder full let it suck the DOT 4 through the system. I let it suck a little extra fluid into the jar and then I switched to the other caliper and did the same. The debris in the lines ended up in the jar. Brakes work great. In my case all of this was done after cleaning the master cylinder and blowing out all the lines.
 

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I'm junking an old frame with the front wheel and the calipers are still attached and appear functional. If you want 'em let me know, will cost you whatever the postage is on the box.
If Franken dont take it, I will...been looking for a frame to mod/cut/chop/weld...Im driving distance too...NY/NJ border, sort of. Thats with the forks too ?
 
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