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Moped Miscellany - No1

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Don't Scorn the Scamp

by J S Lycett

Why is it that, if I am amongst cyclemotor enthusiasts and I mention that I have a Scamp, that I get a look of pity?  As though I am some sort of deprived person.  The Isle of Wight built Clark Scamp is quite a usable machine, and undeserving of a poor reputation.  Having been a long time cyclemotor enthusiast and an Isle of Wight enthusiast to boot, I was delighted when a one time work colleague offered me an old moped for a few pounds; it turned out to be a Scamp.  It was complete but in large lumps.  The drive had failed, of which more later, and the rear wheel had been replaced by a cycle wheel so that it could be used as a pedal cycle.  Fortunately all the parts had been kept so that at some later date some loony (ie: myself) could come along and restore the machine.

It had been first registered in 1969 on that other island, the Isle of Man, but shortly afterwards the owner had moved over to the Midlands and the Scamp had been re-registered in Birmingham.  For those of you not fortunate enough to be familiar with one of these mean machines, the layout is like this ...

Clark Scamp

The Scamp is a small wheeled bicycle with a gear-case in the rear wheel similar to that of the BSA Winged Wheel; the engine is mounted onto the side of the gear-case, but with the cylinder angled up towards the front at 45 degrees and placed well out into the air stream for good cooling.  The Scamp has quite an unusual means of turning the engine for starting.  The final drive is by a large gear, driven by a pinion, which runs in an oil bath.  On the pinion shaft is a centrifugal clutch drum which has a slot machined into it.  On the centrifugal clutch, which is mounted onto the crankshaft, there is a plastic counterbalanced pawl that is lightly spring loaded to bring it into contact with the clutch drum.  As the machine is wheeled forward the clutch drum rotates and the plastic pawl clicks into the slot this now turns the engine.  When the engine fires, and the centrifugal clutch rotates, the pawl overtakes the slot and because it is counterbalanced it swings on its pivot out of contact with the drum; the engine is now ticking over.  As the engine is speeded up the centrifugal clutch takes over and with a couple of twirls on the pedals away you go.

This is, in theory, quite a good method of starting the engine, however there is a snag.  The pawl is moulded out of a rather brittle type of nylon and in most instances the point shears off in use.  This had happened to the pawl on my Scamp fairly early on, which is why it had been turned into a pedal cycle.  Fortunately I had a slab of "Polypenco" which is the trade name of a very tough molybdenum-disulphide impregnated nylon.  It is used as a replacement for Phosphor Bronze in many industrial applications.  I was able to machine a new pawl out of some of this.  A problem was that the original pawl was a many faceted moulding and I was not sure which of the surfaces were important.  Because of this indecision I machined the new pawl to be an exact copy of the original, and this turned out to be quite a tricky job.  With the new pawl installed and the engine overhauled, which consisted of a decoke and replacing the oil seals in the reduction gear unit, I set about smartening up the rest of the machine.

The petrol tank was in good unscratched condition, so I took it down to the local car accessory shop and matched the paint with a Ford colour aerosol.  The frame and tin work had some fine gold lines on, so I took photographs of them before starting to rub them down.  As there was no V5 with the bike I took photographs of the engine and frame numbers in the hope of getting the original registration number back.  I re-sprayed the frame, etc.  and wondered about replacing the gold lines.  I already had a fine felt tip type of pen called a Pilot, which can be obtained in gold and silver from some stationers.  I tried the pen out on a piece of painted scrap metal, letting it dry and then spraying it over with clear varnish.  It worked, and so I decided to try it out on the frame and mudguards.  Here I was faced with another problem, how to get straight or evenly curved lines? I had another brain-wave, very rare in my case.  When we scrapped our old fridge I kept the long magnetic strips that hold the door shut on the basis that they would come in handy someday.  These I found to be just the job, as they would hold on quite well to the frame or mudguard to guide the pen.  For the curves, you could measure the distance from the edge, and for the straight lines you could line them up with a plastic ruler.  I was quite pleased with the results, sprayed over the gold lines with clear varnish and built the Scamp up into a running machine.  The chrome was a bit rusty in places so I cleaned it up and gave it a coat of clear cellulose lacquer.

With the kind help of David Casper I managed to get the Birmingham registration number back, so now that the Scamp was road-worthy I booked an MoT at my favourite motor cycle testing station.  I had fitted the Scamp with one of those ingenious cyclocomputers that can be bought cheaply and are set up very accurately by feeding in the circumference of the wheel.

The Scamp is a very good starter and only has to be wheeled a few yards before it fires up.  It needs the carburettor flooding, the air lever shut, and away it goes, pulling slightly against the centrifugal clutch as the air lever is opened.  I was surprised at the speed and pulling power of the Scamp: flat out in still air the cruising speed is 26.5mph and she will climb most normal hills if you take a run at them.  I entered the excellent "Cyclemotor 100 Mile Run", and the cyclocomputer, which only records whilst the wheel is turning, told me that I had completed 102.35 miles, at an average running speed of 23.5mph, taking 4 hrs 21 mins 2 secs to cover the distance: no mean feat for the Isle of Wight machine.

I find that the ride is a little choppy and that you need to keep a firm grip on the handlebars when at speed; I would put that down to the small wheels and short wheel-base.  Other than that the only shortcoming that I have encountered is that it has been necessary to fit a stay to the rear mudguard similar to the one on the front to prevent destructive sympathetic vibration damaging the previously poorly supported rear number plate.  This is no real problem as there are already lugs on the cycle frame for it.  I have also found it necessary to fit a penny washer onto the lower bolt holding the engine to the gear-case.  This is because petrol/oil mixture seems to dribble out of the carburettor when at speed.  There is a hole in the top of the float chamber cover through which the float needle protrudes in order to be able to tickle the carb.  for starting, and I suspect that this is where the mixture leaks from.  The problem is that when it leaks it runs round the crankcase onto the lower rib of the casting, down the gear-case and onto the rear wheel rim and tyre.  Fitting this washer, which has to be filed to fit round the casting, interrupts the drip of oil and guides it out of harm's way.

From my recent experiences with the Scamp I can thoroughly recommend it as an excellent addition to any cyclemotor enthusiast's collection; it falls naturally into place between the clip-on cyclemotor and the NSU Quickly type in the evolution of the moped.

First published - December 1996

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