Clutch Flush Issue

I did a brake system flush on my 04 R1150RT last week. It went well so I decided to do the clutch while I was at it. The clutch slave and disk were both replaced by the local dealer shortly before I bought the bike a couple years ago, presumably because of a leak, and it hasn't been flushed since then.

There was a little residue in the reservoir, which I cleaned out after I sucked the fluid out. I removed the grub screw and put in a speed bleeder and pumped a lot of fluid thru the system.The fluid that came out looked pretty clean and no air bubbles.

However, before the flush the clutch friction point was about two thirds of the way out of the lever movement but now it's only about a third of the way out. When pulling the lever in, it seems like about the first half of the movement doesn't do anything. If it was a cable system I'd say the free play needed to be adjusted. The clutch seems to work OK but it bothers me that there's so much more free play now. Did I get some air in there or is the clutch master cylinder going out? Any tricks to bleeding it? Or do I just need to put some more fluid thru it?

MarkAZ,

I had a similar issue last spring when I replace my slave actuator and clutch line. Filled reservoir and used a speed bleeder and traditional method of squeezing the clutch lever and pumping fluid "downhill" as well as sucking the fluid "downhill" with a Mityvac. This left me with a similar feel to my clutch lever as you described. I was pretty confident it meant that there was still air trapped in the system somewhere.

Decided to try a different method. Bought a 60cc (~2oz) syringe from a medical supply store. Added a small length of clear tubing to join the syringe to the speed bleeder. After filling the syringe, invert it to get all air expelled and connect tubing to the speed bleeder. Squeeze syringe and pump the fluid "uphill" to the reservoir. You will need to start with the reservoir nearly empty so you don't overflow and make a mess. I don't remember if I needed to have the clutch lever pulled in or just left it alone.

The other problem I had was that I was suspecting air was getting into the system through the speed bleeder threads. I tried to seal it up with Teflon tape. I think it helped some, but there are not many threads that engage to help with the sealing. The other "trick" I was taught, is that when you insert the speed bleeder you are unseating a check ball valve to "open" the system. So even with the speed bleeder, I think air was able to get in past the threads, hence the use of Teflon tape. As you insert the speed bleeder, start the flow of fluid from the syringe. Keep filling the system and as the reservoir fills and you want to stop, start to to remove the speed bleeder at the same time. This will allow the ball check valve to re-seat and seal, minimizing any air to being able to get into the system. Doesn't take much rotation of the speed bleeder between ball check valve open and closed.

I know this sounds like you need 10 hands, but I think I was able to do it by myself, but surely would be easier with a second set of hands. After 1 syringe worth of fluid, check the clutch lever action and see it it has firmed up. I think I did this twice and it returned to the firm feel I had before my maintenance.

Another few thoughts, Turn the handlebars to the right and very lightly tap repeatedly on the clutch lever and you may see some air bubbles come up into the reservoir. Also I was unsure if there was any chance that since the bleed process was done on the center stand, might I need to lean the bike left or right to move any trapped air bubbles. I figured I might find this out on my first checkout ride if I suddenly got a mushy lever, but that never happened to me. Lastly, which you probably already know, keep the paint, dash, windscreen all covered so you don't get brake fluid on them.

Hope this helps a bit. I finally got mine straighten out with persistence, hopefully you will too.

As the prior poster said and as you suspect, you introduced air into the system. Try bleeding it without using a speed bleeder, just use a normal vent screw since the clutch venting head already has a ball check in it.

I did a brake system flush on my 04 R1150RT last week. It went well so I decided to do the clutch while I was at it. The clutch slave and disk were both replaced by the local dealer shortly before I bought the bike a couple years ago, presumably because of a leak, and it hasn't been flushed since then.

 

There was a little residue in the reservoir, which I cleaned out after I sucked the fluid out. I removed the grub screw and put in a speed bleeder and pumped a lot of fluid thru the system.The fluid that came out looked pretty clean and no air bubbles.

 

However, before the flush the clutch friction point was about two thirds of the way out of the lever movement but now it's only about a third of the way out. When pulling the lever in, it seems like about the first half of the movement doesn't do anything. If it was a cable system I'd say the free play needed to be adjusted. The clutch seems to work OK but it bothers me that there's so much more free play now. Did I get some air in there or is the clutch master cylinder going out? Any tricks to bleeding it? Or do I just need to put some more fluid thru it?

Morning MarkAZ

As posted above it does sound like some air (maybe trapped in the line or maybe trapped in the slave cyl).

If all the bleeding that you did (including getting bubble free fluid out of it) didn't remove the trapped air then re-bleeding again probably won't either. (unless you can duplicate the factory method of pushing a large quantity of fluid from the bottom up to the top) -- (remember that air bubbles like to move up on the brake fluid not down so it takes a lot of fast fluid flow to push air down & out the bottom)

My suggestion is (if the clutch works enough to release & allow shifting) to just ride the bike for a ways. Try going up steep hills or very steep driveways then down steep driveways while pumping the clutch lever.

In a lot of cases the engine vibrations will combine the small air bubbles in the clutch fluid into larger bubbles then those larger bubbles will simply migrate UP the clutch line & into the master cylinder reservoir. (air likes to move up on the brake fluid not down)

Also (engine off & sitting still) try pulling the clutch lever all the way to the grip then just slide your fingers off the lever & allow it to SNAP out as quick as possible (this can move the fluid quickly moving the trapped air up the clutch line & out the top)

Before riding (or re-bleeding) be sure to adjust the clutch lever for maximum travel (my guess is that you didn't do this for initial bleeding so you only got a partial master cylinder piston travel during the lever squeezing)-- adjust the clutch lever to be as far away for the grip as possible for bleeding as that gives max piston stroke)

In most cases if the bike is ridable (ie clutch releases enough to stop & shift) then the air will eventually migrate up & then full clutch function will return.

If you have air trapped in the factory fill hose coming from the slave cylinder that air will probably not bleed out by itself so might take a short re-bleed of that hose using your special bleeder screw.

Thanks for the inputs, guys. I'll keep at it & hopefully get it back to normal.

Just to follow up on this...I took the grub screw out of the fill adapter, held it as vertical as possible, and had my wife squeeze the clutch lever while I pressed in on the check ball with a small screwdriver. A couple squeezes and a little fluid bled and now it's back to normal...the clutch grabs about 3/4 of the way out. Problem fixed!

Thanks for all your suggestions. Now for some riding...

Removing the factory bleed adapter from the hose allows you to install a speed (or standard) bleed screw directly into the hose end and get rid of the check ball.

I saw that on another site and I actually tried it but the speed bleeder did not seem to seat when turned in as far as it would go, or at least as far as I felt comfortable screwing it in...it didn't seal. I did NOT want to bugger up that fitting by trying to screw it in too far so I put the adapter back and went from there. Next time I do the flush I'll investigate it further.

I also found out that there's a short version of the speed bleeder. I have the longer version which might have been the problem.

corect - the long one won't give enough thread engagement

BMW sells the proper bleed screw.

Clutch bleed screw

Interesting and timely post. I have flushed several clutch systems, inc. BMW bikes over the years and trust me when I say that they sometimes can be a bugger to get all off the air out of.

1.) I agree that the syringe and reverse-fill process works to minimize trapped air, pushing the fluid up instead of down, but be careful not to overfill and spill on your nice paintwork. I don't often find the need to use use speed bleeders, but have used teflon tape to seal the threads occasionally.

2.) I was bleeding the clutch circuit this weekend on a different brand of bike (Intruder 1400), and had quite a time trying to get it to properly pressurize. This was a very low mile bike that hadn't ever had the clutch fluid changed, and it had absolutely zero clutch engagement when I got it.

a.) Sucking the reservoir clean before I started, I found a bunch of crud/system residue in the bottom of the master cylinder. I cleaned that all out and almost ordered a new clutch MC rebuild kit, but being cheap;

b.) I filled the master cylinder mostly full and pumped three times, then opened the bleeder on the slave cylinder, and then quickly shut it before releasing the handle. I followed this process, topping the MC up periodically until I passed a full pint of fresh fluid through the system. Unfortunately I still never regained clutch action. The system wasn't pressuring enough to engage the clutch.

c.) I removed the master cylinder from the bike, disassembled it, checked the seals and bore, cleaned everything thoroughly (it looked pristine beforehand) and reassembled.

d.) I bench bled the master cylinder (it was pressurizing fine on the bench....cool)!

e.) Re-installed and followed step b. above again with a fresh pint of dot 4. Still no engagement. Ugh!

f.) Attached MightyVac to lower bleed nipple on the slave cylinder and used a combination process of pumping the MC three times, holding the lever in and pumping up the vacuum on the MightVac. Opening the bleeder until the vacuum pressure bled off, closed and then repeated. Still no lever pressure, and now just a bit of cussing on my part.

And then I remembered a trick that I used on brake systems several times last year on various "difficult" bikes......

I pulled the lever in tied it in that position with a piece of nylon cord. I then lightly wrapped on every area of the hydraulic clutch line that I could easily see and touch with a small wrench. I also lightly tapped on the clutch slave cylinder and master cylinder bodies with a plastic mallet. I did this for about 10 minutes and voila. I had decent clutch engagement. Not quite where I wanted it yet, but certainly functional.

Then, as a prior poster suggested, I "flicked" or "popped" the lever quickly several times to "burp" the remaining air from the system. It is a great trick that I use often, and does work. It was better, but still not quite perfect yet. Caution here though, as the fluid can easily shoot straight up when you do this-I always put two or three coins in the bottom of the master cylinder when attempting to pop the lever or bleed the system with the top open, as it really helps to keep the fluid contained in the MC body. Just remember to fish them out when you are done!

Finally, and after a couple hours of dinking it was working acceptably. I took it for a test ride and it was better yet. Came back the next day and the clutch lever was as tight as a drum, minimal pre-engagement play and perfect feel. I have found that sometimes just sitting overnight helps those tiny little air bubbles in the line to consolidate and dissipate.

Upward flush is probably the best, but flicking and popping the lever after a full fluid exchange and lightly tapping the lines, slave cylinders and in the case of brakes, the calipers really helps to remove that last little bit of trapped air. And hydraulic clutches, which are typically lower volume systems, invariably seem harder to bleed than brakes. Or is it just me?

I took mine for about a 150 mile ride today. The clutch felt better than ever. I think it mighta had some air in it before I started this whole endeavor (probably left from when the dealer replaced the slave cyl). Seems to shift smoother too, but that's probably the placebo effect.

So far, so good. Next time it'll be easier, right?