Tech Torque: Basket Case
Our quest to get Stan’s PX200 ready for the new season continues. This month Ron Daley’s turn their attention to its clutch.
The quest to get Stan's PX200 ready for the new season continues. This month Ron Daley's turn their attention to its clutch.
Iapologise for any offence caused to ardent Vespisti but much as I love my PX its clutch is awful, and it's not alone. Thanks to an antiquated design and some rather vague manufacturing tolerances, many PX clutches act more as an ‘on-off' switch than an effective control. Although the ‘Cosa clutch', first introduced on the scooter of the same name and later standardised across 200cc models, was a major step forward it still leaves a lot to be desired. With my PX in their workshops it made sense to ask Martin and Michael Daley to see if there was anything they could do to improve things. As they'll go on to explain, it was also a good opportunity for them to try out a set of BGM's CR80 clutch plates: “Before starting on any clutch work it's necessary to own a couple of Vespa specific tools, namely a clutch mounting tool and a clutch holding tool. We will show later in the feature what these items will be used for.
“Although it's possible to do this work with the scooter laid on its side, this brings a considerable risk of causing damage. We'd recommend using something like the Vespa Survival Kit which lifts the back of the scooter up in the air. This, combined with making sure the front wheel is touching the floor, holds the scooter in a safe and secure way. The first step is to remove the rear wheel – there's no need to remove the rim first, just undo the rear hub nut and manoeuvre the wheel away from the scooter as a complete unit. With the wheel removed it's possible to access the clutch cover which is secured by three bolts. Once the cable's disconnected, remove these three bolts and the cover can be pulled away from the crankcase. Inside the clutch basket you will find the thrust pad and thrust pad clip. These are critical to the clutch's operation as when the rider pulls in the clutch lever this movement is transmitted to the clutch arm by cable. The clutch arm pushes the brass plunger against the thrust pad which in turn applies pressure on the clutch. To remove the pad simply pull the clip, which is spring mounted, and the pad will release itself.
Removing the clutch
“With the pad out of the way it's a simple matter to remove the clutch as it's held in place by a single nut. On older models this will be accompanied by a washer, while more recent P-range engines are fitted with
a flange nut. After securing the clutch with the holding tool, use an 18mm socket to undo the securing nut. There's no need for a pulling tool, the clutch should simply lift away from the crank.
TOP TIP
“At this point it's very important to inspect the inside of the crankcase. We look for swarf and check the condition of the internal oil pump gears. We also examine the oil pinion gear to make sure the shims and circlips are all intact.
Stripping the clutch
“Dismantling the clutch is fairly straightforward. Using the clutch mounting tool, compress the clutch so that the circlip can be worked free. With this removed the plates can be withdrawn. Now, slowly release pressure on the mounting tool until the springs are free of pressure. After removing the springs from the basket, check the bush for any wear on the outside teeth. The bush should drop into the basket smoothly. If the bush sticks halfway or is very tight this needs further investigation and probably a replacement bush. The standard springs are fairly soft, but more than capable of handling the power of a standard scooter. While stronger springs may be of benefit in a tuned engine, it needs to be borne in mind that upgrading to a heavier spring could create ‘clutch drag'.
Clutch plate stack
“The clutch plate stack is made up of the following plates: one thick metal plate, three double-sided cork plates, two thinner metal plates, one metal plate with a small cut-out and a metal plate with cork on one side only. There are a few warning signs you should look for when the plates are ready for the bin. These are that the metal plates become warped (bent), while the cork plates become worn. The latter can be spotted when the corks become less defined. We would also recommend looking for wear on the internal teeth of the metal plates, where they mesh with the clutch centre gear.