Featured article #1

Clutch (view original)

A few notes on the clutch featured on the XJ's:

It's a wet clutch, meaning it soaks in the same oil as the rest of the engine at all times. It features 8 friction plates and 8 plain plates.

The 550 (chain) XJ motor featured some slight differences, discussed in bigfitz' thread here. The purpose of this added complexity seems to be a smoother application of clutch pressure. (?)

A video by fintip, including annotations by xjbikes.com forum members, for changing the clutch friction plates on an XJ650.

Bigfitz has written a great walkthrough with tons of information on the clutch, available here, and reproduced on this page. This page is still a work in progress, and so does not yet feature his images, so for the time being, it is better viewed on the forum.

Well, as long promised, here we go—

CLUTCHES 101: Part 1, the 550 and its brethren:

First item of business: a quick note on the differences between the 400, 550 and 600s and their world-market cousins. They seem to differ a bit in the number and placement of "clutch boss springs" which is covered in detail here: http://xjbikes.com/Forums/viewtopic/t=22927.html so we won't repeat that discussion here.

Suffice to say, this article was done with a North American-market XJ550. If you're working on a Euro or world market bike, or an XJ400/4 or 600, yours will be slightly different.

ALSO NOTE: MOST of what is presented here also applies to the bigger bikes. Their clutches are actually easier, because they do not have the "tabbed" plain plates or clutch boss springs to worry about.

So let's get on with it.

We'll start with the exploded view, annotated as discussed above:


PUT THE BIKE ON THE SIDESTAND, put a pan under it, and let's get the cover off. Putting it on the sidestand means you'll lose little or no oil in the process. On the 550, you'll need to remove the brake pedal and RH rider footpeg to pull the cover.

PRECAUTIONARY NOTE: Any crud or other debris you might dislodge that falls into the bottom of the clutch cavity will end up in the sump. Shove a couple of shop towels in under the clutch basket before you do any gasket scraping, etc.

Here's what I found when I opened mine up for the first time:

What's wrong with this picture, boys-n-girls? Hardware-store bolts and washers. NOT a good idea in this application, those will be replaced.

LOOSEN THE PRESSURE PLATE BOLTS gradually and in a criss-cross pattern:

And DISASSEMBLE THE CLUTCH: Remove all of the pressure and plain plates and the clutch boss spring.

YOU CAN STOP HERE, there's no real need to remove the clutch hub, unless you will be replacing it.

IF YOU DO NEED TO REMOVE THE HUB, the best method of holding it to loosen or tighten the nut is a set of clutch holding pliers:

Be sure to fit a NEW TAB WASHER upon reassembly.

ALTERNATE HUB HOLDING METHODS: You can use a "strap" wrench but be careful of the basket ears; or you can screw or pop-rivet an old plain plate to an old pressure plate, slip that assemblage in, and put the bike in gear. Chacal carries the pliers and they are widely available on-line as well.

NOW THAT IT'S APART: We need to inspect the hub and basket for real wear versus "polishing:"

Note the "wear marks" left by the plates on the hub and basket. Run a fingernail over them, you should not be able to feel any sort of indentations, and your fingernail should not catch.

MINOR indentations can be smoothed out with a polishing stone; but only minor ones. Any major wear means the hub or basket will need to be replaced otherwise the plates will hang up and the clutch will drag or be erratic.

These parts are fine, with the exception of needing to smooth out the "nicks" left by the clutch boss spring on the hub (visible at the left of the pic.)

NOW INSPECT THE PLAIN PLATES: Usually, they just have "etched memories" of the friction plates thay sat next to for so many years, and can be cleaned up and reused:

The plate on the left is as-removed, the one on the right has been cleaned up with Scotchbrite and is ready to be reused.

Inspect for "mushroomed" teeth, or excessive wear/rotational gouges, etc. Don't re-use any plain plate that can't be cleaned up with Scotchbrite to look like new.

WATCH FOR SIGNS OF OVERHEATING: Here is a classic example of a truly burnt clutch plate, this one should NOT be reused:

CHECK FOR WARPAGE: Lay each plate on a small sheet of glass, and make sure it's flat. While the factory allows for "some" warpage, I personally don't re-use warped plates at all, there's no reason to.

Get your (good) plain plates all scrubbed fresh and clean and let's proceed.

INSPECT THE PRESSURE PLATE: As long as it's not burnt, or "torn up" and doesn't have any nasty rotational gouges in its working surface, it will just need to be cleaned up. This one's going to be fine:

After we PREP it: Use Scotchbrite (I use my Dremel, but you can do it just as effectively by hand) to put a nice "non-directional" finish on it, like a new brake rotor:

I also like to polish the area where the throwout washer rides but it's probably overkill.

MORE ABOUT THE HUB: As I said above, there's usually no reason to remove the hub for a "normal" clutch rebuild.

It has a "plain" plate attached to it; if it's loose or gouged up, it will need to be replaced, otherwise DO NOT DISASSEMBLE.

However, you do need to know about it. The plain plate is attached to the hub by means of a wire retaining ring:

Here's a closeup:

If it does need to be removed, the wire ring is released by squeezing the end "loops" together enough for them to pop back out the hole:

NOTE If you do need to remove the wire retaining ring, always replace it with a new one. DO NOT RE-USE the wire ring!

REFINISHING the hub's plain plate can easily be accomplished by sticking your finger with Scotchbrite wrapped around the end, (or the tip of your Dremel) in between a couple of the arms on the clutch basket, and then spinning the hub while you "attack" the surface.

It does not require removal of the hub.

Now let's CLEAN UP THAT COVER, and carefully inspect for any cracks, and inspect the throwout shaft gear teeth for chipping. Now's also a good time to take a handful of q-tips and clean out the oil level sight glass.

Use this opportunity to replace the oil seal at the top of the throwout shaft if it's been leaking. Otherwise, leave well enough alone.

Now's a good time to get a gasket ready; I like High-Tack Spray gasket, applied to the "cover" side only.

Round up all of your new and refurbished parts, and DREDGE THEM IN FRESH OIL:

I HIGHLY RECOMMEND using NEW factory bolts and washers, and NEW SPRINGS of your choice.

AND LET'S GET READY TO REASSEMBLE: First thing that goes in is a friction plate:

FOLLOWED by a PLAIN PLATE; notice that this first "tab" is straight up:

Then ANOTHER FRICTION PLATE, followed by a plain plate, note the orientation of the second tab:

Then another friction plate, followed by a plain plate, this is the orientation of the THIRD TAB:

CONTINUE ASSEMBLING, FOLLOWING this diagram for the tab orientation,

Until you get to your SIXTH FRICTION PLATE, which is the "special" one with the larger ID and the clutch boss spring:

(This belongs in the 3rd position from the outside, which is the sixth plate as you reassemble.)

NOTE: Bikes other than North American Market 550s may have two clutch boss springs and special friction plates as in the original exploded view.

I'm never sure exactly what to do with the FINAL TAB, since the book only goes to 6; so I position it at 180 degrees to #1:



The wafer bearing goes on the "pull"rod, then the hardened steel washer to protect the aluminum pressure plate from the bearing;


And get it READY TO REINSTALL on the clutch pack:

Be sure to ALIGN THESE DOTS cast into the hub and pressure plate when reinstalling:

INSTALL your SPRINGS, BOLTS AND WASHERS, and gradually snug down in a criss-cross pattern:

Now let's carefully TORQUE them to specs, which on the 550s is ONLY 5.8 ft/lb:


-"Glue" your gasket to the cover;

-completely remove the throwout lever and spring from the end (top) of the throwout shaft.

-position the teeth on the throwout "pullrod" facing to the rear, in approximately this orientation:

And wiggle-fit the cover back on; snug and then torque the cover bolts.

THEN, rotate the top of the throwout shaft CLOCKWISE (viewed from above) until it STOPS, and reinstall the lever, return spring and clip.

The lever should end up so that when pressure is applied from the rear it STOPS as indicated here:

Screw your top adjuster (at the lever perch) in about halfway.

Reinstall your cable, and "raw" adjust it at the bottom, "fine adjust" at the top so that you have 1mm-3mm free play in the cable, and you're good to go!

So, that should cover the basics of a clutch overhaul on any XJ, and the granular specifics of doing a 550/600.

As always, let me know if I missed anything you'd like to see in better detail, or if you have any questions or need anything clarified.

COMING SOON: In the next chapter of "Clutches 101" we will pull apart the clutch on my ratty old 650 Seca and see what we find.

Happy wrenching—- Fitz

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