Changing your clutch


Fairly simple and straight forward job, one specialist tool is needed, the clutch compressor. Other tools needed will be general sockets, spanners and screw drivers.

First job is to put the new set of clutch corks into a bath of oil use an old saucepan or similar and use ST90 gearbox oil, you can use it later to re-fill your gearbox. If you put dry plates in they will very quickly burn out.
The right hand side floorboard has to come off. One bolt from the bridge piece, two nuts from either end of the outer trim is enough to be able to take this off.

Next also take the leg off that the rear of the floorboard sits on, this has to be done to gain enough clearance to take the chain case side off.
Next up is the exhaust, there should be a clamp where it meets the down pipe, two 13mm nuts where the big bracket is, and a smaller 10mm nut at the end of the tail pipe. Some original and most notably the TV exhaust will also have a bolt fixing into the underside of the engine casing, at the rear of the box section of exhaust.

One last thing, you may need a block of wood to tap the exhaust away from the down pipe if the exhaust has not been removed for some time.
Now undo all the remaining 10mm nuts to allow the casing to be taken off. If the casing has not been off for a while or a chemical gasket has been used, you may find that you will have to tap (with a rubber hammer) the chain casing to become free.

If you see a small gap appearing and the chain case is still "locked on" a small screwdriver gently prizing the gap larger, working around the whole casing may help. Do not force it though, as damage will occur!
Now your chain casing is free, just unhook the cable and nipple from the clutch arm, you are now ready for your special tool!

There are two main types of compressor available, a two legged one and a four legged one. Either is fine to use, but if you do use the two legged one, make particular attention to the legs being tight onto the studs. The compressors work buy you attaching them to the studs in the chain case, if you use bolts, you may need to find some studs to fit with the two legged type.

Align the tool to make sure that it fits over the centre of the clutch housing (it has a nipple on it), then fix by method as above. You are now ready to turn the centre part of the tool into the clutch.
This is the compressing part of the tool, as the clutch sits on a bed of springs, the springs become compressed. If you look closely, their is a larger circlip ring around the out side of the top plate. With the clutch compressed sufficiently, prize one tip of the circlip out, gently moving round. You will find that is may suddenly pop out, don't worry about this.
You can now start unwinding the compressor tool, the clutch will be free and come out. Note how they come out, top plate, cork plate, steel, cork ,steel cork etc.!

While you have your scooter stripped to this state, many people take advantage of this and choose to check the tightness of the end plate bolts. But again you will need a special tool to do this. A clutch holding tool, it looks similar to a cork and steel welded together. It has teeth both on the inside and out, to hold the basket and housing together without damage. In no circumstances should you jam these with a different tool to obtain this effect, damage WILL occur.

With the tool in position, it simple slides into the basket, the locking washer that is tabbed over the large centre nut will need to flattened away from the nut. A 24mm socket will be needed with an amount of force to undo the nut. Then simply slid the two housings away. 11mm nuts secure the gearbox end plate, just make sure they are all tight, not over tight though or you will easily strip the threads.

Re fit the clutch housing and spider, making note of either the centre brass bush or two needle roller bearings are in place. Tighten 24mm nut as hard as you can, and re knock over locking tab washer, you are now ready to continue with the clutch.

You can quite happily re-use your old steels, just make sure they are clean, a bit of sandpaper will do this, and not warped. If they are warped or you are unsure of their condition, replace them.

You will need to check that your corks and steels slide smoothly up and down in the basket, if their are any grooves cut into the basket and outer bell, they will need to be filled flat otherwise clutch drag will occur. The last thing to check is the outer housing has two halves riveted together. Any play in these and again drag will occur, replacement is the only cure.

Fit the clutch spider into the rear sprocket, in just goes in on the bearings/bush. Notice the legs of the spider, the top edge is like a castle effect, then after this the shafts of the spider should be smooth, if yours has ruts or lumps it is worn, either file flat again or replace.

A tab waser locates on any one of the pins with it's eylet, the clutch nut can then be tightened down by hand.

Fit the clutch holding tool, do not try to use screwdrivers or anything else to trap or jam this, damage will occur, these tools are very cheap and very neccesary.

Using the best socket and ratchet you have, simply get this nut as tight as you can, there is no torque setting other than really tight! Use a screwdriver and hammer to knock over one edge of the tab washer onto the nut, this is done to stop the nut comming un done.

The clutch springs, and here we are using a centre spring as well due to the tuned engine. When checking your clutch springs, you should stand all five up, they need to be all the same height.

To stop the springs from falling, especially if the engine is still in the scooter, simply dab one end of the spring in grease before fitting.

By dabing the grease on one end of the spring, this can now be placed in its recess in the ctutch spider, it will help to keep the spring in position

Carry on until all five are in place

Fit the clutch basket, again it has recess in it for the springs to sit in, plus the legs of the basket will need to align with the legs of the clutch spider. Onto this goes a clutch cork

After the first cork, put a steel plate on this, then cork etc

Carry on until the last part which is the steel top plate, this has a chamfered edge on it and is thiker then the other plates. GP top plates differ to all other models by being thicker.

Now we need to use the clutch compressor to compress the clutch basket and springs.

When this is done you can slide the corks and plates down into the housing, they should slide down pretty freely with no interferance.

Continue to compress so that the top plate is under the grove in the leg of the clutch spider. Now you can fit the clutch retaining circlip, where the two ends meet they should be placed so that both ends fit inside a leg.

All that remains now is to fit the chaincase side gasket, if you have a non GP/DL machine make sure the top clutch thimble is in position.

Put the chain case side back on, re hock up the clutch cable and nipple, although you almost certainly will need to re adjust this later, you can do it anyway! Refit all 10mm nuts around casing, then exhaust, floorboard leg and floorboard, do not forget to refill your gearbox either. A half a litre of ST90 will suffice.
You now need to adjust the clutch. Clearance in the clutch control cable is essential, their should ideally be 1.5mm of free movement between the lever and its housing. Too tight and the clutch will drag and too little the clutch will not release properly and slip will occur
That's it!