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Clutch Master Cylinder problem

3384 Views 17 Replies 6 Participants Last post by  skoto1
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I have a problem I've never encounter before. My clutch master on a GL1200 slowly builds up pressure until the clutch starts to slip. If I bleed off the excess pressure down at the slave cylinder, it works okay for 10-15 clutch lever pulls, then the lever becomes hard to pull, and soon the clutch will slip again.

I have rebuilt both the master and the slave, and every thing is clean and moves freely, but the problem did not go away. The hole from the reservoir into the piston is clean and not clogged.



I put a different master cylinder on from a GL1500, and the clutch worked just fine on a 3 hr ride. I can't leave this one on the bike though, because the 1200 has the chock lever built into the housing, and also has the radio switch mounted to it.



Any ideas
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This has to be simply an MC gone bad, seeing how the one off the GL1500 worked fine for you.
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Hard to believe a "bad" m/cyl is the cause of your problems - the only reason you should encounter an "engaged" m/cyl while riding is because of some contamination in the hydraulic lines/enclosures. This could be air or water, but it certainly would not be forcing out the master cyl piston if system is clean and properly bled.

I have encountered this before in a brake system (virtually the same) where the heat of the pads caused the air in the caliper to expand and engage the brakes to the point of lockup. Simple bleeding eliminated the problem.

Suggest you diassemble the slave cyl and clean the rubber seal and seal groove carefully. Bleed system thoroughly, as soon as all air is out go for a ride. If problem continues, suggest you diassemble the m/cyl and clean there as well, but it is pretty hard to visualize the master cyl forcing pressure down to the slave cyl... this is just a last resort.

Good luck!! TS99
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I'll bet if you take the lid off the clutch master cylinder you'll find the small port under neath the little tin piece in the bottom of the reservoir is plugged. The purpose of the small port is to relieve pressure build up in the system when the lever isn't pulled. Once you have to top off the reservoir, and lift out the float you'll see a fairly good sized hole in the bottom of the reservoir. There should be a small piece of tin pressed into the raised collar around the larger hole. Pry the tin, Honda calls it a protector, and check the small hole that was covered by the other end of the tin piece. If that hole gets plugged with crud just clean it out and you should be good to go. If that isn't the problem it would be a good time to order a rebuild kit and redo the master cylinder.
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Yes- that was the problem. I discovered it was blocked a couple days ago and got it working correctly-

Thanks for all your good replies!
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What exactly did you do to clean it out? I have an 84' 1200 Interstate.... I rode it last in August. I went to go prep for a ride for Veteran's Day this week and noticed the clutch had no pressure... I checked the master and it was pretty low and the fluid was a bit dirty.

Here are a few questions that I need help with....

1. How do I remove the tin protector inside the master cylinder without damaging it?

2. How is the best way to clear the whole under that tin protector?

3. How and where exactly do I check and bleed the line?

4. How and where exactly do I bleed the Slave Master?



I am trying to get this done by Wednesday's ride? I am new to motorcycles and have only had this bike since July..... so any and all help and pics would be greatly appreciated!!!

Thanks!
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the bleed for the slave is above the swingarm on the back of the engine. you may just have to flush and bleed. after you have cleaned out the master cylinder resivoir i would ad fluid to the resivoir of the master cylinder and start the bleeding process. pull the clutch lever a few times and hold it. then loosen the banjo bolt on the master cylinder let it drain and then retighten then let go of the handel. do that until you have no air coming out there. then repeat at the slave cylinder until you have clean fluid coming out. you should get your clutch pressure back. but you may have a leaking slave cylinder if the master is low. check your oil level and make sure the slave is not leaking into your oil. some have used a pump for this which is quicker i didn't.
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thanks for answering my questions.



I believe I found where it is..... not a whole lot of room to work on it....

If after I do what you suggested and I don't get the pressure back, when I check the oil, what am I looking for? If it is leaking, will I need to drain the oil and refill?

Would you suggest that I rebuild the master and the slave or replace them?


Again, sorry for the newbie questions but I am needing all the help I can get since I am solo on doing this myself.

What size wrench is needed to loosen the banjo bold as well as the nipple for the slave that you know of?

Thanks again for all the help!
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TAWFUN wrote:
Here are a few questions that I need help with....

1. How do I remove the tin protector inside the master cylinder without damaging it?

2. How is the best way to clear the whole under that tin protector?

3. How and where exactly do I check and bleed the line?

4. How and where exactly do I bleed the Slave Master?
1. Just pry it out, you may have to spread out the little prongs that hold it in so it will stay when you press it back in place.

2. I use a wire from a wire brush held in a small vise grip or pliers to poke the hole out.

3. Skoto gave you the info on bleeding the clutch. I usually stick a piece of vinyl tubing on the bleeder with the end of the tube in a small can that has enough brake fluid in it to cover the free end of the tube. Then make sure the reservior is full, squeeze the lever slowly in and hold or tie it down. Open the bleeder slightly with a wrench (it's best to loosen it first) and shut it once the fluid stops coming out. If you get any air bubbles coming out repeat the process making sure you have the lever held down until the bleeder is shut. I would try bleeding just the slave cylinder first, once the small port is opened I doubt you'll need to bleed at the banjos. Maybe, but I doubt it.

4. The bleeder is on the back rear of the engine.

You can get replacement rubber parts for the bleeder. Look at Motogrid on the web, they sell replacement parts and show exploded drawings with parts numbers for you bike. Get yourself a set of metric end wrenches, Harbor Freight is a good source if you have one nearby. I don't remember the size you need, probably a 12mm for the banjo and a 10mm for the bleeder but that's not certain. A normal set usually has open and box end wrenches from 8-15mm, check the link below.


http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42305
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it is a little tight. if you have someone help it's easier but you can do it alone.once you squeeze the lever you can strap it or clamp it like a third hand.i beleive it's a 12 and an 8 maybe 10 haven't had to do it in a while. if your low on fluid it went somewhere and if you don't see a leak it's probably leaking where you can't see it on the inside. your oil level will be high and maybe thinner than usual but if it hasn't leaked much you want be able to tell just watch the level and if it drops again you know it's leaking and if you don't see a leak it's the slave leaking into your engine. they are fairly cheap on here and feebay depends on your ablity and pocket book if you rebuild you know what you have. if your not sure if it's leaking into your engine change the oil and be safe. again watch your level and if it does it again you'll have to rebuild or replace. keep the questions coming we where all newbees once this is how we all learn. i'm still fairly new at this but i have already learned a great deal from this wonderful sight. want find a better place to learn.
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Bot h of you guys are outstanding in your responses and I really appreciate it.... I will give those things a try at first light tomorrow and see how it goes. I will post up how it goes.....

Thanks again!
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UPDATE......

Ok, so I did not have a lot of time today like I had hoped and I ran out of light quickly before I had to call it a day.

I went ahead and attempted the bleed..... when I opened the slave nipple I only had a little fluid come out...... when I went through the procedure, nothing would come out of the slave nipple......

I have topped off the master, even used the piece of wire suggested to clean out the little pinhole under the tin protector inside.

Still, nothing.....


I will try again in the morning early..... our Vet Day Parade ride isn't until 11am...... so far though, not looking good.
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you really should start at the banjo fitting at the top if your not using a pump to speed things along. make sure you don't release the handel until you tighen the banjo back and the same on the slave bleed nut or it will suck air back in and defeat the purpose. it only took me 2 days of trying until i finally started at the top and worked my way down. if the slave is bad it may never come back until you swap out the slave.

just a thought in reading your post if you did it only once you've just started it will take several attemps to get the pressure up.
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This little tool is very handy to have for bleeding brakes and clutch systems.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92474

These cost a bit more but have many uses in any shop. I use mine for brake and other hydraulic work and for testing ignition vacuum systems. Either one is worth the money if you'll be working on your 'Wing.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=39522

I like the Mighty Vac because you can use it to apply pressure as well as vacuum. Often it's faster to pump brake fluid into the bleed screw and push the air out the top after you've drained the system
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exavid..... how to I use them for this.... what are the step? This way I hook it up correctly....

thx!
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you can also use a spray bottle pump if you have one of them handy and a hose to hook it to your slave bleed.
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Hey there guys!

First off, I want to say thank you for not only the help but also the fact that these forums exist!!!!!

I didn't get my bike up in time to make riding in the Antioch Veterans Day Parade with The Patriot Sentinel Riders like I had planned.... I was supposed to meet the group at 8:30 am this morning but didn't get my clutch problem fixed until almost 11 when the parade started.

HOWEVER, thanks to the fantastic help from you guys, my clutch problem is FIXED!!


Thank you so much! I am back on the road!! FINALLY!
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sorry you missed the parade but at least your riding glad your going. ride safe.
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