Clutch bleeding for the VTX 1800

Preface
This is a walk-through for bleeding the hydraulic clutch on the VTX 1800 - the process should be identical regardless of the model. I see so many riders on all makes/models with clutch and brake fluid which looks dark brown like Coca-Cola. I assume many of them don't realize that this is a sign of old fluid which needs to be replaced. Since the performance of brake fluid degrades so slowly most of us don't even realize how bad the fluid was until we replace it with fresh stuff via a bleed. Having clutch related problems? Perhaps you just have old fluid - often times a quick bleed is just what you need to get the bike feeling "right" again.

What makes brake/clutch fluid turn brown?
In it's pure (fresh) form brake fluid cannot be compressed (unlike air and certain liquids) and it is designed to have extremely high boiling points. This makes it ideal for a brake and/or clutch system. Each time your brake and/or clutch system gets used air slowly makes its way into the fluid - this air contains small amounts of water vapor. Brake fluid absorbs this moisture from the air over time and the contaminants in the water discolor the fluid. This is why brake fluid containers always say "only use fluid from a sealed container." Over time the water vapor and contaminants that infiltrate your hydraulic fluid lower it's boiling point and make it slightly less effective. This results in that "spongy" pedal or lever we feel from time to time with old fluid.
Synthetic fluid is designed to resist water absorption and therefore last much longer between bleedings. This is why I recommend and use Valvoline SynPower DOT 4 fluid - plus it's clear which allows you to easily see when it's time to replace it. This coupled with the fact that it's readily available at just about every auto store I've ever seen and it only costs about 5 bucks per quart makes it a great choice.

If you're interested to learn more about brake fluid including the differences between DOT 3/4 fluids and DOT 5 you can read Biglry's informative post in this thread.

Before you start working you might consider buying a vacuum pump as an alternative to a one-man bleeder kit. You can get these just about anywhere nowadays from Harbor Freight, Sears or most auto stores for about $30. If you plan to bleed your own clutch and brakes on the bike it's well worth it. If you ever think you might use it to bleed the brakes on your car/truck/etc then it's only more of a bargain. Since I bought mine I've used it more times than I can remember and each time is a reminder of how much easier it is versus the old hand pump method. Also if you ever plan to change your lines to braided stainless or otherwise do a full break-down and rebuild of your brake system a vacuum pump will get air out of the lines that a regular bleeder just won't get.

If you're rebuilding your clutch hydraulic system or replacing your lines with braided ones and the system is completely dry be aware that it will take longer to bleed and you must be very careful to get all the air out of the system. You'll need to work the clutch lever a lot to get the air out of the master cylinder and you should pump the lever to build pressure in the system and crack the banjo bolts loose to make sure and get out the air that likes to "hide" in there.

As with all projects undertake this at your own risk, but this is a pretty simple process if you take your time and are careful. Don't forget that brake fluid eats paint, so when you're preparing remember to have a lot of rags handy to help protect all your paint!

How a bleeder screw works
The bleeder screw is what allows us to bleed any hydraulic system. Here is a pic I worked up to help show how it works:

The grey area represents what the bleeder is threaded into, whether it be a brake caliper, a clutch master cylinder, etc.
The red represents the fluid which is backed up behind the bleeder.
You can see the hole in the side of the bleeder, this hole is connected inside the bleeder screw to the hole we see at the top of the bleeder where we attach the rubber hose when bleeding.
You can see the taper on the end of the bleeder, this helps make a tight seal when the bleeder is snugged down. The area the taper sits on in the caliper, master cylinder, etc is called the "seat"
When we loosen the bleeder screw it allows fluid to flow past the seat, through the small hole on the side of the bleeder and out the top of the bleeder where we have our hose attached. Based on how this works you can see how you need to be careful not to obstruct the hole in the bleeder near the seat. This is especially important if you're removing the bleeder to put teflon on the threads.

Preparation/supplies

5mm allen

Phillips head screwdriver

10mm wrench - it must be a wrench, a socket won't work.

LOTS and LOTS of rags to protect your paint and to catch spills. I also use an old sock to catch spills at the reservoir

1 pint of fresh (sealed) DOT4 brake fluid (a quart if you're doing brakes too) - I use Valvoline SynPower 4

Mity-vac or other brake bleeding kit

Bungee cord - optional

Process
Before you start COVER YOUR TANK!!! Brake fluid eats paint so make sure you have sufficient protection in case you make a spill.

You can do this project on the sidestand or on a lift, just decide in advance. If you're doing it on a lift you will need to bungee or tie the front wheel at full lock to the right side like this:

The last thing you want is for you to bump the wheel or have the wheel swing with the reservoir open and sling brake fluid (which eats paint) all over your bike. This is why we tie the wheel in place.
If you want to work on the bike on the ground then swing the wheel all the way to the right and the tire should provide enough friction (on level ground) to hold the reservoir level where we want it. If you're still uneasy then I would recommend tying the wheel just to play it safe.

The key reason for doing all this is to get the reservoir roughly level. With C bars at full lock to the right you get this, if you have other bars or have adjusted your bars so that the reservoir won't level out this way then you may need to break the riser clamps loose and rotate your bars so the reservoir sits level. Remember that if you do this snug the clamps back tight once the bars are rotated or else you might end up with a ding in your tank and brake fluid everywhere - always better safe than sorry.

Now on the left side of the bike remove the 7 5mm allen bolts holding the chrome cover on and carefully remove it and set it aside out of the way so you don't damage it.

That gives us access to the clutch slave which is where we need to be to bleed the clutch.

Back to the reservoir - with it level wrap a sock or a towel around it to protect against any spills. I like old socks because they wrap nice and snug around the reservoir.

With the sock/towel wrapped around the reservoir remove the 2 screws holding the cover on with a phillips screwdriver. With the cover off have a rag handy to remove the "internals" under the cover. If you have a chrome cover with chrome screws you can use a piece of heavy plastic (like most of our parts ship in) between the screwdriver and the screw to prevent knicking the chrome.

In order from the top down you have the cover (1), the set plate (2), the diaphragm (3) and the float (4).

They come out in the order they are stacked in the picture, set a rag aside and lay these parts on the rag while we bleed the system.

At this point we have to choose which type of bleeding we'll be doing, vacuum bleeding or old-school pump-bleeding. Make your choice and scroll down to the appropriate header in the walk-through and proceed from there.

Vacuum bleeding
Remove the little rubber cover on the bleeder screw, in the pic you can see I've already popped it off.

Keep in mind that with a vacuum bleeder sometimes it pulls so much vacuum that you get a little bit of air leakage around the threads of the bleeder screw. This leakage results in tiny air bubbles in the fluid during the bleeding process (they resemble foam). This is normal when using a vacuum bleeder and should not be taken as a sign of trapped air in the system. If you are concerned about this inhibiting your progress then you can remove the bleeder screw and wrap it with teflon tape (like you use on plumbing fittings). The teflon tape helps seal the threads and prevents these tiny bubbles from showing up during bleeding, you should note though that this is not mandatory to ensure a good bleed.

Place the 10mm wrench on the bleeder with enough space to swing the bleeder open about 1/4 to 1/2 turn and then firmly place the hose for the vacuum bleeder onto the bleeder screw.

Wrench and hose on bleeder - this is on a brake, but it looks the same
If you look closely there is a little ridge below the top of the bleeder, make sure the hose gets over this ridge as it helps provide a good seal when you put the system under pressure from the pump.

Ridge on the bleeder
Before you proceed read the entire bleeding process below until you understand it, this will prevent having to figure out what you're doing half-way through the process and possibly making a mistake which could make your work harder.

Bleeding any hydraulic system using a vacuum pump requires a balance of:

Making sure you maintain pressure on the vacuum pump

Making sure you don't run the reservoir (on the handlebars) empty

Making sure you don't spill brake fluid on anything

Making sure you don't fill the entire vacuum pump reservoir

Pump the vacuum up until you have a good bit of pressure built up, the manual for the pump specifies a PSI, I just pump the crap out of it and it works fine.
Now using the 10mm wrench crack the bleeder open 1/4 to 1/2 turn so that fluid starts to be drawn into the vacuum pump reservoir. At this point you want to keep a close eye on the handlebar reservoir, when the fluid gets close to the bottom of the reservoir close the bleeder and top off the reservoir with fresh fluid from the container. Make it a habit to grab a rag when you go to pour so that you'll have it handy to help prevent spills and drips.
With the reservoir topped off check the pressure in the vacuum pump and crack the bleeder open again so fluid starts flowing. Keep an eye on both the reservoir and the fluid coming out of the bleeder. The idea is to make sure we have no air bubbles coming out from the bleeder and as we flush the old fluid out we should begin to see fresh clear fluid coming out at the bleeder.

At this point if you feel there is no more air in the system and you can see fresh fluid coming out at the bleeder than close the bleeder and squeeze the clutch lever a few times - it should feel solid not spongy. If it feels spongy then bleed a little more to see if there is air trapped in the system, it may help to pump the clutch lever a little and tap the banjo bolts where the line attaches to the reservoir and the clutch slave. Sometimes air likes to "hide" in the banjo bolts. Keep at it until you have fresh fluid throughout the system and a solid feeling clutch lever.

Once you're done bleeding skip to the bottom for the rest of the directions to finish and button everything back up.

Pump bleeding
Remove the little rubber cover on the bleeder screw, in the pic you can see I've already popped it off.

Place the 10mm wrench on the bleeder with enough space to swing the bleeder open about 1/4 to 1/2 turn and then firmly place the bleeder rubber hose onto the bleeder screw.

Ridge on the bleeder

If you don't have one of those little "one man bleeder kits" then place the other end of the hose into a container to collect the fluid as we bleed the system.

Before you proceed read the entire bleeding process below until you understand it, this will prevent having to figure out what you're doing half-way through the process and possibly making a mistake which could make your work harder.

The process of pump bleeding a hydraulic system is a simple one that just requires a little coordination.

Pump the clutch lever several times to build pressure - on the last pump squeeze and hold the clutch lever

Loosen the bleed valve 1/4 to 1/2 turn until fluid starts to flow from the bleeder and into the rubber hose

When the fluid has stopped flowing (or slows down) close the bleeder - do NOT release the clutch lever until the bleeder is closed!!!

Release the clutch lever slowly

Check the level of fluid in the reservoir and top it off if necessary

Repeat all of the above

What happens is we build pressure in the system using the clutch lever and we release that pressure through the bleeder screw. We have to hold the clutch lever until the bleeder is closed or else the release of the lever will draw air into the system from the bleeder - we discussed earlier why we don't want air in the system.
As you run through the steps above the first time let the reservoir run somewhat close to empty before adding fresh fluid. This will help ensure that most of the old fluid is out of the reservoir before we start adding fresh stuff. Beyond that just keep repeating the steps above until you get fresh fluid coming out of the bleeder and you feel there is no more air in the system.
With the bleeder closed squeeze the clutch lever a few times - it should feel solid not spongy. If it feels spongy then bleed a little more to see if there is air trapped in the system, it may help to tap the banjo bolts where the line attaches to the reservoir and the clutch slave. Sometimes air likes to "hide" in the banjo bolts. Keep at it until you have fresh fluid throughout the system and a solid feeling clutch lever.

Once you're done bleeding skip to the bottom for the rest of the directions to finish and button everything back up.

Finishing up
Remove the bleeder hose making sure not to spill any fluid and make a mess. Tighten the bleeder snug but don't really wrench on it, it only requires 4.3 ft/lbs to seal - hand tight with the wrench will suffice. Place the little rubber cover back on the bleeder.

With the bleeder closed let's close up the reservoir so we don't have any spills. Fill the reservoir with fresh fluid to the ridge inside:

And then slowly and carefully reinsert the inner parts in the reverse order you removed them in. Carefully drop the float (4) into the reservoir, then slide the diaphragm (3) into place and the set plate (2) should slide right into the diaphragm.

With everything in place install the cover and snug the screws down - these are hand tight as well only requiring 1.1 ft/lbs to seal. If you have a chrome cover with chrome screws remember you can use a piece of heavy plastic to prevent knicking the chrome.

Now you can reinstall the chrome side cover:

These bolts only require a few ft/lbs to snug them as well, hand tight with a wrench will suffice.

Clean up any fluid you might have spilled, remove all the rags you had put down and if you bungee'd the front wheel undo it.

That's it - you're done - congratulations!

Afterthoughts
This is a quick and easy job once you've got the experience from doing it a few times. It can help cure some clutch problems and is ideally something you should do as regular maintenance about once a year depending on how many miles you log on the bike. By using a clear fluid like Valvoline SynPower you can tell by a quick glance at the sight glass when it is time to replace it. If you bleed your brakes and clutch at the same time you'll even be able to tell which you use more often by which discolors sooner.
Try it one time replacing old fluid and you'll notice a drastic difference in the feel of the lever - old fluid degrades so slowly it's hard to realize how much effectiveness you've lost.