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Front Brake Lever Piston / New Brake Lines

nightengale

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I'm getting closer to to road ready on a '82 CB750 Custom. The previous owner had let the bike sit, but his brother installed a new plastic brake reservoir on the brake lever and gave me all new front brake lines (all the way down to the calipers). Installed those, but their full of air at the moment.

My question is: How do I tell if the brake lever piston works correctly (good seal)? It moves freely (under spring pressure) via the lever or even when I push on it with my finger. I don't want to remove the piston if I don't have to (not sure I have to right tool to get the clip out). I don't live close to anything, so figure I should ask first.

The dust cover on the piston looks to be in great shape, it's even possible it's already been rebuilt.

However, with fluid in the reservoir, no brake fluid comes out of the brake lever brake hose connection (hose is disconnected). I can see the piston move back and forth, but there's no brake oil coming out.

I don't know how to safely remove the plastic reservoir either (should I need to, to inspect the oil holes). Does this just snap in and out?
 
It's not working right if the point up to the first joint won't show filling up. There is a hole you can see piston in and another with a super small pin hole that absolutely must be open to pump the line with fluid, the smaller hole usually corrodes up plugged. Pretty sure reservoir does not remove to see those holes, you already mention seeing one, the other is there as well.

Proper when full of fluid will have the handle go down partly to get tighter, so tight that past a certain point you cannot move it any more with no leakdown at all at that point.
 
The plastic reservoir has a clear round (like a washer) bottom with three holes drilled in it. They line up over the holes in the metal base, including the super small pin hole. However, the plastic reservoir really is in the way when trying to push a very fine copper wire into the pin hole. No luck so far. It's either too soft a wire, too large a wire, or the hole is too clogged, not sure yet. A larger wire didn't work (.014).

How does this plastic reservoir attach? Is it clipped in somehow? How is it removed? Don't want to break it.

Is there any chemical spray I can use to try to unclog the pin hole, like carb cleaner? Or is this going to ruin any seals down there?
 
Plastic reservoir merely sits in place sealed by an o-ring, the through screws for cover hold it down. Corrosion can easily lock it in place. The small hole often clogs with hard enough deposit to seem like concrete. Anything you use with petroleum distillate will harm the brake seals. I use a hand held pin vise with small drill bit to drill down a bit through the corrosion (do NOT use a drill!!) to define the smaller hole location and then use wire to get through it.
 
Ok, thanks. Followed your instructions and got the brakes bled.

Removed the reservoir, it wasn't stuck, but the o-ring was sure tight, so prying it up carefully was required. That gave me far better access to the troublesome pin hole.

I then used a very fine wire, which got the hole going again. Then was able to switch to the .014 wire (much stiffer) and it just fits as I hoped, and used that several times to ensure things were clear. Posting that here in case anyone wants to know what size fits.

Put everything back together and bled out the lines. Kinda a hard job by yourself, but got it done. I had already removed the calipers and put them on a ladder. Was able to put the calipers on a upper ladder step, chest level, then crack the bleeders open while compressing the brake lever. Also used plastic hose to return the oil back into the brake fluid bottle while keeping an eye on the reservoir.

Once things pressurized a bit and I had most of the air out (all lines were new so this took a while), put the calipers back on, and finished bleeding the lines. Seem to have good brakes now. It's got new calipers and new pads, should be good to go.

Took the bike for a spin too, but not very far. Few more things to get done before I do that (carburetor issues).
 
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