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Discussion Starter #1
I can bleed the brakes and get a good feel on the master cylinder lever but after it sets overnight it takes several pumps of the lever to get any brake lever felt resistance and the cylinder is not losing any fluid.
Feels like a weak master cylinder pump. When I do get slight front braking I can go for 20-30 seconds riding the bike and no immediate brakes again on the hand lever until I pump the lever several times. This is still the 1987 OEM cylinder.
I can get a complete new cylinder from Amazon with free shipping for $28 or a OEM Honda master cylinder re-build set for $40 Honda part number 45530-471-831.
I've never had much luck re-building automotive Master cylinders for long life, I usually just replace the cylinder.

Does the OEM cylinder usually re-build ok or should I go with this Amazon Clone complete cylinder???????????or maybe take the OEM cylinder apart first and do a internal bore inspection for rust pits or??????????

The fluid in the cylinder looks good and clean because I completely cleaned and rebuilt the front brakes couple years ago.
 

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Hey Okie!
Sometimes air rises in the fluid tubing—especially that top bend—it’s hard to bleed it out.
Pop the seal at the bottom of the master cylinder to see those two holes are clear. Get the bend out of the top of the tubing. Jiggle the lever to see if you can get remaining air out—you’ll see bubbles in that first hole.

these are easy to rebuild BUT you’ll need a good set of ring pliers to unlock the ring holding in the piston.
 

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Discussion Starter #3
Hey Okie!
Sometimes air rises in the fluid tubing—especially that top bend—it’s hard to bleed it out.
Pop the seal at the bottom of the master cylinder to see those two holes are clear. Get the bend out of the top of the tubing. Jiggle the lever to see if you can get remaining air out—you’ll see bubbles in that first hole.

these are easy to rebuild BUT you’ll need a good set of ring pliers to unlock the ring holding in the piston.
I'll look at the bottom of the master cyc for them two holes. That is not even mentioned in the service manual. I've got all kinds of tools for internal and external clips, etc.
What are the chances of dripping brake fluid onto the plastic, etc when doing work on the cylinder while it on the handlebar. Brake fluid ruins things fast.

So you are saying just bend the tubing down or maybe loosen the bolt at the brake line and turn it down somewhat?

I can bleed the brakes easily instead of removing any old plugs in the bottom of the cylinder. (surely those are not rubber plugs??) I have two ATV's and the Honda just sets at rest quite a bit and your theory makes sense.
It has been about 2 years since I last bleed the brakes.

Do you guys trust the cheap clone replacement master cylinders that I mentioned. Seen them on flea bay for $22 and free shipping??????????????

That is good info you provided.

Thanks and Stay Safe.
 

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Yeah brake fluid will damage paint and discolor plastics.

no need to loosen brake hose. See that little kink in the hose right before the master cylinder? Just turn the handlebars left a bit to lower that kinked piece.

then in the bottom of the mc, there’s a black rubber puck. Pry it out with a thin flat blade screwdriver—from the rim not the center. Then you’ll see two holes—Jiggle lever to allow any trapped air to escape through the first (inboard) hole.

150564
 

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I used an OEM piston rebuild kit from Rocky Mountain or Partzilla which i thought was $16? Four years ago? I think the knockoffs are a more gamble than i want.

main thing with the piston is dried crustiness in the fluid can cause leakage past the seal and eventually damage it. Sometimes the bore gets damaged too.

on my last build i bought a NOS cylinder on ebay cuz my sight glass was bad. They are hard to find at any price. Let me know if you can’t fix it—I’ll give you my old one it still works but the glass is real bad.
150565
 

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150582


150583
Pics of my worst master cylinder—here’s the holes I described
terrible pitting in bottom of the piston bore this one may never ride again
 

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Bleeding brakes properly isn't as easy as it seems. If you pump the brakes until you get pressure you are putting air in solution. Release pressure and the air boils out. Buy a large container of brake fluid. Get some clear hose and a glass jar. Set the jar on the floor or blocks and cut the hose so it just touches the bottom of the jar. Pour about 1/2" of fluid in the jar. I like tall skinny jars. Remove all fluid from the master cylinder and wipe out. Pour in new fluid and pull the lever back just enough to open the ports and get and air out from the top side. Open bleeder screw on the wheel cylinder and watch for fluid flow. It it does flow gravity will do most of the work for you. If not, crack the pull the brake lever and tighten the bleeder before you release the lever. Repeat until the fluid is fresh.
 

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Discussion Starter #9 (Edited)
56S:

Yes you are correct. about bleeding brakes and just injecting air, etc. I used to bleed brakes like that on auto's so as I did not have to have a helper until I got the mityvac optional brake bleeding kit that I use with my mityvac Vac/pressure pump.

I now have a MityVac combo pressure?Vac unit with the optional brake bleeding hose kit.

If you have never used such you need to give it a shot. Very user friendly. It sucks the air out of the system and I start at the longest brake line run.
You might see such on You Tube. If you are not familiar with such try searching How to bleed brakes using a mityvac pump. Here is one link to such. THIS GUY IS FILLING THE MITYVAC CONTAINER TOO FULL. You have to keep a heads up and not fill the container that full because if it get sucked into the mityvac pump it will ruin the pump's diaphragms. (and then a $20 pump repair kit will be required) Note that you can suck out the old fluid and you can see the clear hose when air is no longer being removed and the fluid is clear with no bubbles. (what is user friendly is the Operator is in constant visual control operating the vac tool observing the air and fluid being removed by just applying the Vacuum)

I also crimped off the brake line FLEX HOSE at the CHINA clone MC and still no good response from the MC. The MC HAS BEEN GETTING WEAKER AND WEAKER FOR ABOUT A YEAR, but the front brakes are not my priority brakes on this rig, I mainly always used the rear brake for good braking and the front as just kinda of an assist so I was not too concerned until the front went to no brakes at all.

Thanks for your reply, appreciate the reply.

Stay Safe.

Here is the link I referred too:
 

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air in the lines ?, or your not adjusting the shoes all the way out BEFORE you go bleeding them ?. pair of vise grips, full bottle of brake fluid is all you need, YOU DO NOT NEED ANY STUPID BRAKE FLUID BLEEDER TOOLS !. if any of this fails ?, then your plunger in the master cylinder that has the seals on it are bad ?, or...your return hole that goober ^^ showes in his picture is stopped up ?.
 

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Yes, I have a mighty vac and that's what I use but find it sucks air around the bleeder threads.
 
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