Basingstoke_Scooter_Club » Page 10 of 18

All Vespa two-stroke scooters are all very simple and the de coke instructions laid out below are the same, with minor variations, for all Vespa scooters. This article is aimed at the novice owner who might like to try simple jobs to keep his or her scooter on the road without having to pay a garage for the pleasure.

This sounds a little pessimistic, as with the use of semi synthetic oil and a reasonably fast riding style this de coke period could easily be doubled in most peoples’ books. The PX pictured in the article showed 20,000 Kms on the clock and had only been de coked once before. The owner was unsure when the last de coke occurred. The carbonising was found to be minimal as the pictures indicate.

The scooterboy favourite, the PX, featured here needs minimal maintenance and is virtually bullet proof into the bargain. The PX is a two stroke and as such will need, from time to time, a de coke. When it comes to how often the engine should be de coked the owner must use the advice in the service station manual – every 4,000 Kms.

Remove the side panels. This will reveal the engine on one side and the spare wheel on the other. Remove the spare wheel (This job can be undertaken with the spare in position, but it makes it a little awkward to access all the wheel nuts).
Loosen the five13mm (spanner size) M8 wheel nuts to the rear wheel. Jack up the engine in some way, so the wheel can rotate freely. An old car type scissor jack is excellent here. Remove the wheel. This may sound odd to the novice, but Piaggio liked to hide the main bracket to the silencer and its retaining bolt behind the suspension pivot arm and this bolt is cunningly situated in line with the centre of the rear tyre.

Remove the silencer. The standard issue is held in place by the aforementioned bolt (17mm spanner size) and the pinch bolt around the top of the exhaust down pipe (Usually 13mm). On removing or releasing these fixings the silencer can often be wriggled free from the engine. If it won’t come free, squirt WD40, or similar, around the top of the down pipe of the exhaust and leave it to soak in for a few minutes. Some ’coaxing’ with a hammer and a wooden drift is sometimes felt necessary. If you decide to use the ‘hammer and drift’ ploy, please be aware that if you are hitting something hard with a hammer, you’re probably not going about the task in the right way? So be aware of the consequences of your actions and look for reasons why the item is stuck. The reason might not require force?

Remove the cylinder cowling. This is made of a plastic material, but earlier Vespas have steel cowls. This cowling, on the PX, is held in place by two cross- headed screws, at the side and a 13mm (spanner size, again) bolt at the front of the cowl. There will be some variation on these fixings on earlier Vespas.
The cylinder head can now be removed complete with spark plug. This is held to the cylinder studs by three standard M8 (13mm spanner sized) hex nuts and a long hex nut that was used to secure the cowling bolt in place. There should be one plain washer and one spring washer under each nut. The head is now free to be slid off the studs.
This is ‘it’ as far as tackling a strip down for the basic de coke. Some like to slide the barrel off the studs to better clean the exhaust stub of carbon, but this is not really necessary and requires more work and a cylinder base gasket to complete. The exhaust port can be quite effectively cleaned of any trace of carbon deposits with the barrel in situ. Just exercise a little care that loose carbon does not contaminate the bore of the cylinder, that’s all.

Best to read this carefully, as this is where the ‘Ace mechanic’ can cause more problems than he solves!
To clean the carbon off the inside of the cylinder head is quite straight forward if you remember that the head is made of relatively soft aluminium. If you scrape off the carbon with, say, an old screwdriver (these are made of much harder metal – steel - of course?), the likelihood is that you will remove the carbon deposits and scratch the inside of the head into the bargain.