'79 R65 Front Brake Locked, Can't Open Tank & Unknown part

[at1rest]

Hi there, ('79 R65 Front Brake Locked, Can't Open Tank & Unknown part)

I had a chance to do some closer inspection of the '79 R65 today and discovered a few problems.
1) The front brake is locked up. The brake lever is just flapping in the breeze
see video: [youtube]https://www.youtube.com/watch?v=5djt9CPTwJY[/youtube]

and there's no spongy give when applying (squeezing) it all the way.
It's as if it's hitting a brick wall.

I titled the front wheel up with my shoulder under something in front,
it's on the center stand, so I just wanted to see if the wheel would turn at all. But it won't move.
It seems that the hydraulics are all connected and there's fluid in the tank but I'm really not sure what to look for.
Is there a quick fix just to be able to roll it?
Any other thoughts?
I'd love to be able to trouble shoot this all the way to a reliable repair but will need some guidance.

2) There's an unknown brand new part I found tucked in the fairing pocket.


Can you tell me what this might be? (Hopefully a fix for the front brake)

3) I can't get the gas cap off. The key obviously unlocks something about it because when not unlocked it only turns a little but.
After unlocking I lift the hoop on the top of the cap and can spin it in both directions but can't seem to catch the threads for it to
lift out of the tank. (Leftie loosie)

The R85 has a USA Dime (10 cent piece) glued over the key hole on the gas cap so no worries there. It just unscrews fine so I know what to expect from the R65 but no luck.
Any thoughts on this?

Oh, by the way, I did find the key on the R80.
It was just folded down in the key hole in the fairing.

Thanks!

Steve

[SteveD]

The part is a master cylinder piston. The repair involves removing the original one, inspecting the bore and resleeving if it's corroded.

Does the 79 have a handlebar mounted master cylinder? The return hole can block and lock the brakes. Remove the cap and remove the fluid. Have a look into the tiny return hole and see if you can loosen any crud in the hole.

Removing the fuel cap can be as simple as tugging it vertically very hard. The usual description is..a rope thru the handle, then around your shoulders/back of neck, stand on the pegs and pull! Really! Some advise against that though...http://www.largiader.com/articles/gascap/

[SteveD]

If you get the cap out you'll need to do something to prevent it happening again.

The whole shebang is just crimped together.



If you can loosen the cap, turning it to line up these holes, then wedge something in there, the thing won't spin. I use a small piece of wire, then the black plastic surround helps to keep it in place. It's worked for years like that, but I occasionally redo it.

No drilling required. The alternative technique involves drilling from the top.

Not all caps have both holes, but mine has 3 of each.

[at1rest]

The part is a master cylinder piston. The repair involves removing the original one, inspecting the bore and resleeving if it's corroded.

Does the 79 have a handlebar mounted master cylinder? The return hole can block and lock the brakes. Remove the cap and remove the fluid. Have a look into the tiny return hole and see if you can loosen any crud in the hole.

Removing the fuel cap can be as simple as tugging it vertically very hard. The usual description is..a rope thru the handle, then around your shoulders/back of neck, stand on the pegs and pull! Really! Some advise against that though...http://www.largiader.com/articles/gascap/

The "master cylinder piston" ... could that be where the problem is and why the previous owner purchased a new one?

Yes. The '79 has a handlebar mounted master cylinder.
I'll try your suggestion about removing crud from the return hole.

This, however, makes me wonder if there's a way to loosen a tube at the caliper and let the fluid run out there?
Wouldn't that accomplish the same thing in releasing the brake?

I'll read the link to the fuel cap snafu and try a few things and see what happens.

Thank you!

[Seth]

Regarding the fuel cap...you wrote:
3) I can't get the gas cap off. The key obviously unlocks something about it because when not unlocked it only turns a little but.
After unlocking I lift the hoop on the top of the cap and can spin it in both directions but can't seem to catch the threads for it to
lift out of the tank.

I think you've got it backwards. When "locked", the cap spins. When you unlock the cap, the upper portion of the cap engages the lower threaded portion. I've had this situation. When the gasket gets old (part 17 in the fiche, part number 51 25 1 453 148), the cap gets stuck on the tank. Unlock the cap (so it only turns a little bit) and then try really hard to spin it off. You may need to use something to get you better leverage. Maybe a bar through the hoop of the handle, but better a wooden screw clamp layed down on the tank so you can put pressure on the entire handle instead of just a couple of points. Hopefully you can do it without damaging the cap. If you get it off, replace the gasket and it shouldn't get stuck again.

Regarding the brakes, I'd assume this bike has been sitting a long time and both the caliper and master are frozen. You may want to start by removing the brake line from the caliper. Then remove the bolts that secure it from the fork. See if you can get the caliper off the rotor or if it's stuck on. If stuck, you may need to hit it. Try using a wooden block with a hammer to reduce damage. If it's not stuck, you should be able to press the piston back into the caliper.

As others have written, the part is the piston from the master cylinder. Assuming it was leaking all along, the fluid is gone (which is why the lever "flaps") and moisture got in the system which corroded everything.

Good luck.

[Rob Frankham]

Regarding the fuel cap...you wrote:
3) I can't get the gas cap off. The key obviously unlocks something about it because when not unlocked it only turns a little but.
After unlocking I lift the hoop on the top of the cap and can spin it in both directions but can't seem to catch the threads for it to
lift out of the tank.

I think you've got it backwards. When "locked", the cap spins. When you unlock the cap, the upper portion of the cap engages the lower threaded portion. I've had this situation. When the gasket gets old (part 17 in the fiche, part number 51 25 1 453 148), the cap gets stuck on the tank. Unlock the cap (so it only turns a little bit) and then try really hard to spin it off. You may need to use something to get you better leverage. Maybe a bar through the hoop of the handle, but better a wooden screw clamp layed down on the tank so you can put pressure on the entire handle instead of just a couple of points. Hopefully you can do it without damaging the cap. If you get it off, replace the gasket and it shouldn't get stuck again.

Regarding the brakes, I'd assume this bike has been sitting a long time and both the caliper and master are frozen. You may want to start by removing the brake line from the caliper. Then remove the bolts that secure it from the fork. See if you can get the caliper off the rotor or if it's stuck on. If stuck, you may need to hit it. Try using a wooden block with a hammer to reduce damage. If it's not stuck, you should be able to press the piston back into the caliper.

As others have written, the part is the piston from the master cylinder. Assuming it was leaking all along, the fluid is gone (which is why the lever "flaps") and moisture got in the system which corroded everything.

Good luck.

+1 on the cap, it is designed to rotate freely when 'locked' and unscrew when it is 'unlocked'. If after trying, though, you still can't get it to move, the 'accepted' remedy is to take a piece of rope and thread it through the handle, then stand on the foot pegs, bend over the tank, wrap the rope round your shoulders and heave!!!. This will pull the top off the cap leaving the threaded section open to view where you can get at it. Off course, this will mean that the cap is in bits but, most times it can be reassembled.

Rob

[at1rest]

Seth: Ahhh ... very good on the tank cap. I understand now.

Yes the bike has been sitting for more than a year.
There is some fluid in the little tank on the handle bar but I haven't checked the level or the color / age.

***
On the "piston from the master cylinder" ... is the master cylinder up on the bars and the end on the brake handle is what presses against one end of that piston to push the fluid through the tubing?
***

I'll first try the "get the gunk out of the return hole" in the reservoir and then continue with your instructions if that doesn't release the lock up.

Thank you!

[at1rest]

Hi Rob,

Thanks for confirmation on the gas cap.
I think I'll be heading over there (1/2 hour drive) shortly to have a go at it.

Steve

[Rob Frankham]

Seth: Ahhh ... very good on the tank cap. I understand now.

Yes the bike has been sitting for more than a year.
There is some fluid in the little tank on the handle bar but I haven't checked the level or the color / age.

***
On the "piston from the master cylinder" ... is the master cylinder up on the bars and the end on the brake handle is what presses against one end of that piston to push the fluid through the tubing?
***

I'll first try the "get the gunk out of the return hole" in the reservoir and then continue with your instructions if that doesn't release the lock up.

Thank you!

I think it's very likely that the master cylinder is stuck. That substantial spring on the piston is intended to push it back to clear the 'return hole' and release the pads. If it is, the best bet will be to disconnect and remove the master cylinder (it can be removed from the handlebar mount by undoing two allen screws). That way, a) the brakes may well release so at least you'll be able to move the bike, b) you can take the cylinder home and work on it at your leisure and c), if, as I surmise, the piston is stuck, you can insert a rod through the outlet port to knock it loose.

Rob

[Seth]

Yes, the master could very well be stuck.
If you loosen the bleeder on the caliper to release the pressure, you can try rotating the tire. And yes, the master cylinder is on the handlebar with the reservoir. You need to remove the bolt the handle pivots on. The handle presses in on the piston. There is an inside circlip keeping the piston in its bore.