Gearbox pulley
June 2008.
As I had the gearbox out and needed the pulley off, it seemed silly not to strip it at least for an inspection. There was some wear at the rear circlip but little else seemed bad. Some form of compression is needed to take apart and reassemble the unit. I made one from some threaded rod and bits from under the bench. One does not want the spring flying out under tension! The two pulley halves are also rotated apart and want to fly back over the cams, they need letting back gently. I used a vice and a strong grip to unwind and wind them back.
Once this hazardous operation is complete, the compression can be taken completely off. DO NOTE which holes the spring comes out of! There are several choices giving different tensions to the spring.
The cam, spring and inner pulley half then slid off. Two areas internally showed some wear or light damage on mine. The large bearing area that takes all the sliding and twisting loads showed wear of the plated surface. Eventually this may need replacement, as yet I have no wear limit data for the part. I cleaned the muck and staining off with some chrome cleaner.
Next, the sliding pulley inner face sits up against a circlip and washers when it is closed. The inner face was scarred a little by the circlip ends. Why? The circlip sits crooked as there is a grub screw adjuster shoving it across. Check the picture - the shim washers are dented.
What I did with that is turn the circlip around until the flat part was in line with the screw, not the eye ends. I've no idea if it will stay there but made me feel better at least.
The last part I did something to was the back face of the cam. The main circlip pictured earlier sits under pressure against the alloy, and eats its way slowly in. If the clip recedes enough, the cam will migrate towards the gearbox. It may hit a mounting bolt or even fall to bits. At the very least it will let the belt drop into the pulley more easily, raising the gear ratio.
I decided to fill the recess with a mild steel shim, hand made and glued in place with metal filled epoxy.
Stuck in and clamped, it made a fairly neat job. I used JB-weld. Possibly it could have managed without glue. Spot the key way? I did in fact file this section out of the shim as well, but the photo wasn't as good as this one.
All that remained was to reassemble, (don't forget the key) twisting the pulley halves back about 1/3 of a turn against the spring to re-engage the ramps and then compressing until the circlip could be fitted.
Back on the gearbox (nut tightened against a rope again - torque unknown as I don't have a figure) it looked like the pulley might need a little adjustment. I got the idea from somewhere (wish I could find where!) that the pulley at rest should have the belt flush with the pulley top. Mine was down slightly. Slacken the grub screw to let the pulley close.
And that was it. Running the car afterwards, it is apparent that the engine is revving higher. Whether due to the new rear engine mount (another page!) or the circlip shim, or me getting the spring not quite right I don't know yet. Certainly the shim will have moved the cam inward and closed the pulley about 1mm. The belt adjustment above will ONLY affect the gearing at take-up, first gear if you like. The pulley will come off the stop almost immediately. The car is actually pleasant to drive like this, as previously it was dropping the revs against slopes and headwinds, giving a heavy engine vibration coming I suspect through the dying rear mount. The 180 degree crank engine smoothes out a bit at higher revs. I shall leave it "as is" for now and see how it runs and what fuel usage is like.
Long term report on that - seem to have lost up to 5mpg but this could easily be due to wear or other causes too. settled about 75mpg.
Update - October 2010 and 10,000 miles later, the circlip ate
the end off the steel pulley centre, letting the back half of the pulley rub on
the gearbox, mount plate and nearest bolt. Not great damage but a replacement
pulley required. 
Ok, got a pulley from Rossefields, next day delivered, but they aren't cheap :o( Here is a picture of the old circlip after it had been sandwiched between the pulley and gearbox for a short while.
It had made surprisingly little mess, though I did decide to replace the gearbox seal ( and bearings again) while I had the thing out. The pulley would not come off the shaft without dropping the box a bit. The edge of the pulley catches the bulkhead moulding below the battery. What a pain if ever I just want that off by itself? Here is the new one.
I think I know what most of the number means! The spring goes into hole "A" at the bottom in this picture. Note the new style wear tips on the ramps.
And into hole "3" in this one.
And the pulley half is marked "12degrees" so "24" degrees between both halves. Makes sense? Well even if it's a load of twaddle it will help me remember which holes the spring came out of if I ever have this one apart.
There is still a mystery left. There is no adjustment screw in this pulley (the fairly new belt sits near the pulley outer rim at rest). There is a tapped hole but it is too far out to press the washers inside, and seems to serve no useful purpose. The hole goes right through the outer half of the pulley and is tapped M6 x 1mm. Some sort of manufacturing aid? Anyway I thought it may prove useful some time in the future for a home made puller, so I tapped the other 2 holes as well. It only took minutes and I can't see any harm in it.
One other thing I did to the pulleys was fit some new "red blocks", the plastic sliders for the weights in the variator / front pulley. The metal weights were beginning to rub inside the cone and developing a small flat on their edge.
Running the system now, the engine revs are lower, and the acceleration up to 20mph more eager, perhaps the latter due to the belt taking up quicker. Previously there was a short lag as the engine built up some revs in the heavy flywheel.
Aixam