CX / GL 500 / 650 Clutch

updated 3-Aug-07 to include Turbos

If you have difficulty in engaging neutral whilst the engine is running, see the very end of this page, about clutch adjustments - BEFORE stripping the clutch!

This page shows you how to remove, strip, renovate and refit the clutch mechanism on your CX or GL. The clutches are generally very durable, and should not require any major work for at least 40,000 miles, although the operating cable is unlikely to last this long. Servicing the clutch assembly is easy, and does not require radiator or engine removal.

All nut and bolt sizes are given for the spanner size required to fit them.

I am very receptive to comments and suggestions, but you use these pages at your own risk. The clutch in the photos was from a 1980 CX500Z, but this is common to to the Z, A, B and C models. There may be very minor differences compared to the 500 Eurosport and 650 models.

Skill : 2. Personally dirty : 2. Work mess : 1. Space : 1. Time : 2-3 hours.

Skill levels explained.

Tools : 8mm, 10mm sockets, extension bar and ratchet; pliers; clutch nut removal tool (or strong screwdriver and rubber hammer); degreasing and cleaning agents (dishwasher ... !). Clutch cover gasket, Hylomar or soft sealing compound. Torque wrench. For Turbos : 12mm and 14mm sockets.

How the clutch works

As you pull the handlebar clutch lever, this pressure is applied to the clutch cable which consists of a static outer sheath containing a moving inner cable. This is usually known as a Bowden cable. The bottom end of the inner cable passes through a mounting point cast into the lower right of the front crankcase, and is attached to the clutch actuating arm. This passes through the clutch casing outer cover. As the cable is pulled, the arm moves upwards, forcing a cam out of the centre of the inside of the outer casing. The cam in turn forces out a mushroom-shaped thrust plate which pushes against a roller bearing embedded in the clutch retainer.

The clutch itself consists of an outer basket (left) which is driven directly from the nose of the crankshaft; thus it is turning whenever the engine is running. The outer basket has deep slots running up the sides of the basket.

The clutch inner basket (right) has gear-like slots on its outer circumference. In between the two baskets, to provide the friction which connects the crankshaft to the gearbox, are a series of circular ring plates, some with teeth on the inner face, and some with teeth on the outer face, alternating. These plates engage with the outer or inner baskets. The sets of plates are pressed tightly together by the four (six on the Turbos) clutch springs, which are held in place on shaped projections of the retainer. The inner basket fits onto the gearbox input shaft, being retained by splines.

As the cable is pulled, the actuating arm rises, the cam is operated, the mushroom thruster projects and pushes down (physically, this is inwards, towards the engine) the inner basket, against the strong pressure of the clutch springs. This causes the clutch plates to separate just enough to allow the set which engage with the outer basket from moving round the set which engage with the inner basket.

So, the motion of the outer basket is not transmitted to the inner basket, and the engine turns without moving the gearbox.

Phew!

Clutch removal

ALL BIKES : to minimise oil loss, put the bike on the centre stand and with a block of wood under the front of the engine casing, jack the bike to raise the front wheel and make the engine oil flow to the rear. There is a little oil loss during a clutch change, but this is not significant.

TURBOS : Remove the 4 screws holding the chin fairing and that then drops off. Remove the 6 bolts which retain the turbocharger bracket (the stainless steel shield-shaped bracket at the top of the clutch cover) and either slide the bracket fully to one side or remove it completely. Now proceed as below. I recommend replacing these bolts with stainless steel capscrews.

With a cold engine, loosen by 4 or 5 turns, but do not remove, the 8mm head bolts which fasten the round clutch cover to the front right engine cover. Now pull the clutch handlebar lever in and the pressure down the cable should pop off the round cover. This saves you having to prise it off, and possibly damaging it. Neat one, huh?

With the cover loose, slacken right off the 2 x 10mm nuts which lock the bottom of the clutch cable to the casting on the front crankcase, and let the cable fully relax. Use your pliers to raise the actuating arm to the almost vertical position, and slide out the nipple at the bottom of the cable, releasing the cable. Slide the cable out of the cast-in supporting bracket, and push it out of the way. If the cable shows any sign of wear - probably at the nipple end - replace it with a new one. I don't recommend pattern parts, they never last as long as the genuine article.

Remove all the 8mm bolts and pull off the round cover. The gasket is best renewed; clean all traces of it from both the round cover and the engine casing. Don't lose the mushroom-shaped thrust plate from the inner centre of the round cover. You can buy 0.8mm gasket roll from Ebay for a few pounds and then cut almost all the engine gaskets for a just pence each - and ten minutes' work.

Slacken, in sequence of about 4 complete turns on each, the bolts which hold on the retaining plate. Note that the pressure from the clutch springs is quite substantial and by undoing then in sequence, you avoid stressing them. When the final bolt has been loosened and removed, remove the star-shaped spring holding plate and the clutch springs. Don't lose the roller bearing from the centre of the star plate.

Photo (right) shows inside the front crankcase. (Here the front cover happens to be off, but you don't need to do this to service the clutch.)

TURBOS : have SIX sets of springs and not four as in the picture opposite. Otherwise it looks almost identical. See that two of the six retaining bolts are different to the others - they are shouldered. Make a note of which holes these came from.

In the centre of the clutch mechanism is a round black steel nut (left) with four slots cut deeply into it. This is a very tight fit on its shaft and may be difficult to remove. Put the bike in top gear and get someone to apply the footbrake. Some mechanics cut a suitably sized spanner from a piece of pipe or an old socket, but most home mechanics simply apply a strong screwdriver to one of the slots in the black nut and hit the other end of the screwdriver with a hammer. This explains why almost all of these clutch retaining bolts show considerable battle damage, and if this the case, renew the nut.

Pull the entire clutch assembly forwards, disengaging it from the crankshaft.

Renovation

On the workbench, place the entire clutch basket so that the gear teeth are lowermost, and pull the inner basket upwards. It doesn't matter if the clutch plates come out with it or not; but withdraw and separate the plates and the two baskets. The bottom of the inner basket is the flat plate with the upwards-projecting pillars, over which the clutch springs were located.

The easiest way to clean all the bits is to wipe off all surface oil, and the wait until the wife is out before putting everything in the dishwasher. (Run the dishwasher on an empty cycle afterwards to clean out any residual oil.)

Whilst the dishwasher is running, you may want to polish up the clutch cover - see the page on Polishing The Aluminium.

With everything clean, examine the clutch plates. There are actually FIVE different sorts, and you need to identify them. First sort them into two piles, those with teeth on the inner and those with the teeth on the outer, circumference.

The "Type A" or inner-teeth set are easily identified because they are steel, and have tiny dimples on their surface. There are two types of these. Only one is a double sandwich plate (left), and the rest (right) are not. Easy one.

There are five non-sandwich plates for the 500cc engines, and six for the 650cc and Turbo engines.

In this photo (left) the two types of inner plate are shown side by side, for comparison. On the left is the single plate, on the right is the double "sandwich" plate.

A close look at the bottom face of the photo shows the tiny dimples, just visible underneath my fingers.

The plates with teeth or lugs on their outer face are called "Type B" and come in three classes:-

There is one single "Type B" plate with score marks cut into the black friction material, running straight outwards, and has outer lugs noticeably wider than the other plates.

Here (left) the single thick tang "Type B" plate, held against the ordinary outer plate, and the wider tang is clearly seen. Put this plate to one side.

Secondly, there is another single outer plate which is visibly thicker (right) than its partners. Locate this plate and put it aside. In the photo, it's the lower of the two.

The remaining outer-toothed plates should be identical, and there are five for the 500cc engines, and six for the 650cc and Turbo engines. These have score marks cut at a pronounced angle into the black friction material.

Wear limits

Measure the thickness of the plates and the length of the clutch springs.

Clutch spring minimum lengths : 500cc engines 1.2795" / 32.5mm; 650cc engines 1.4921" / 37.9mm.

500 Turbo spring limit is 34mm but I found that whilst my 500 Turbo's springs were well within this limit, the clutch was slipping and I fitted heavy duty springs and friction plates from M&P - cost about £55.

Clutch plate thickness : Type A is 0.1032 - 0.1094" / 2.62-2.78 mm, service limit 0.0906" / 2.3 mm; and Type B is 0.1378" / 3.5 mm, service limit 0.1221" / 3.1 mm for all five plates for the 500 or all six plates for the 650)

500 Turbo minimum thickness : 3.1mm but see note above.

Always replace the clutch plates as a complete set.

Reassembly

Insert the plates as follows, as per the photo (left):-

1. The Type B (outer) plate with the wider tang.

2. An inner Type A (steel) plate.

3. A Type B (outer) plate.

4. The double "sandwich" Type A steel plate.

5. Alternating Outer Type B and Inner Type A steel plates (4 sets remaining out of the 5 for the 500cc, 5 sets out of the six for the 650cc and Turbos).

6. Finally the thicker outer-toothed Type B plate.

The photo (right) shows the clutch, after all the plates have been assembled onto the inner basket.

Line up the outer plate tangs so that they are all as straight as possible.

Either insert the retaining plate into the underside of the inner basket (left) or drop it into the outer basket (right).

Slide the inner basket into the outer basket and wriggle the plates down the slots. Don't worry if the inner basket disengages from the inner plates, but if this happens, you will have to wriggle the inner basket back down the plates again. This is dead easy to do.

This is what it looks like when it's all back together again. From this photo you can easily see why one of the Type B plates has the wider tangs - they are the only ones which engage in the correspondingly larger slots at the top of the outer basket.

Also, here you can see where the sandwich plate lies in the stack of other plates. I can't quite make out what the sandwich plate actually does ... I'm open to suggestions.

The big steel collar goes in here, and acts as a bearing. Note the oil feeder hole, make sure this is not obstructed with any dirt or debris.

If your renovated clutch is going into a spares box, spray everything liberally with ACF-50 (aka "Magic Shuggy Juice"), rotating the inner basket inside the outer basket, to get the lubricant into every nook and cranny. Then spray every outer surface and wrap the assembly in newspaper and plastic bags.

Reassembly onto the engine

This is a straightforward reversal of the disassembly.

Taking care not to disturb the assembled clutch baskets, slide the clutch as a complete unit onto the gearbox input shaft, engaging the splines. Check that the gear teeth on the outer circumference of the outer basket have engaged with the primary drive pinion on the nose of the crankshaft. The inner basket should now still rotate independently of the outer basket, although it may be a little stiff to move.

Fit the steel washer over the centre of the clutch shaft; this washer (left) has the word "OUT SIDE" stamped on it, here just visible between my index and middle finger. The word should be facing outwards, i.e. towards the front wheel.

With the gearbox in top gear, and the rear brake firmly applied, fit the black retaining nut, this goes on with the chamfered side facing inwards towards the engine. Tighten to 58-72 ft lbs / 8-10 kgm. In practice it is difficult to get this right as some torque wrenches do not go above 50 ft lbs.

(To those of you without the right tools, do it up BLOODY TIGHT is all I can say. About 8 on the Grunt Scale when you hit it with your screwdriver and hammer.)

Slide each of the clutch springs over its locating pillar and place the star-shaped retaining plate with its dished face inwards towards the clutch. Ensure that the small bearing in the dead centre of the star plate has not been lost or displaced. Fasten each bolt finger tight. At least one correspondent has had a bolt break off when tightened to the Honda recommendation of 10 ft lbs, and so have I, so I now recommend that you use a locking compound on the thread and tighten to no more than 8-9 ft lbs.

TURBOS : see on the inner basket that two of the threads on the spring pillars are recessed. These are where the two special bolts go. BE CAREFUL not to put the wrong bolts in or you may split the pillars.

Check that operating the actuating arm is moving out the mushroom thrust piece, and using a new gasket and sealing compound, replace the round clutch cover, tightening the 6mm head bolts to no more than 6 ft lbs. These are VERY easily stripped, so be careful.

Reattach the clutch cable and test the action. Make major adjustments at the bottom end by slackening or tightening the two 10mm nuts which retain the cable against the casting lug. Contrary to popular belief and the Haynes Manual, one 10mm nut should be above the casting, and one below it, thus locking the cable in place. When correctly adjusted, there should be no more than 1/2" of free play measured at the ball end of the handlebar lever.

If you have difficulty in engaging neutral whilst the engine is running, make adjustments here BEFORE stripping the clutch! Also, many clutch problems are solved by simply fitting a new operating cable.

How to prolong clutch life

Clutch slip (engine accelerates but the bike doesn't) and clutch drag (difficulty in changing gear and selecting neutral; bike edges forward even with the clutch lever pulled right in) is best investigated and corrected as soon as it occurs. Begin by checking that the adjustments are correct, and that the inner cable slides freely up and down. Drip light oil - gun oil or sewing machine oil - down the cable, from the handlebar end. If in doubt, fit a new cable. I generally carry a spare clutch cable.

Very often, clutch slip is caused by using synthetic or semi-synthetic oil, especially in the Turbos. DO NOT USE anything but bog standard mineral engine oil, without additives of any sort.

As you change down the gearbox to decelerate, give the engine a good blip of throttle. This gives you a much smoother ride, and saves no end of clutch wear, as the road speed will be better matched to the engine speed. Also, on a slippery surface, it really helps prevent a slide.

Pull the clutch lever in when you start the engine, even if you are in neutral. This means that the starter motor doesn't have to turn the clutch inner basket and gearbox as well as the crankshaft, and saves starter motor wear. This also holds good on your car, where this is a hallmark of a trained driver (as well as holding in the button of the handbrake, when you apply it!).

Whilst you CAN change gear without using the clutch, both up and down the gearbox, this is not recommended. It needs a great deal of practice, especially changing down, to get a seamless change, and prolonged clumsiness can only accelerate gearbox selector wear.

You are welcome to comment on these pages.