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by D Greenhill

I own two Mosquitos: a 38cc Crossley from 1951 and a 49cc Garelli from 1952(?).  Neither are currently on the road, although the Crossley is undergoing an overhaul, with the hope of seeing 1998 on two wheels.  I say hope, as I have found a problem with which other Mosquito owners may be familiar and may be able to help with.

The drive roller not only provides drive (in the dry!) but also acts as a rotating magnet for the magneto.  On stripping the engine I found what I thought, at first, where oil smears on the alloy housing for the magneto.  I gave it a good clean and to my dismay I found that the "smears" were actually cracks - lots of them.  They appear on the outer perimeter of the housing, where obviously the force is the greatest.  Has anyone else come across this problem and found a solution?

I have had new crank and magneto seals manufactured and I'm about to get the armature rewound, but I'm reluctant to undertake this if the machine is to be reduced to a static exhibit when the roller eventually fails.  Can anyone help with a cure or a spare roller?

A little history

I acquired the machine from my father in 1962 at the tender age of 16 - my first motor cycle!  He in turn bought it from a work-mate in 1954, it having had two previous owners; the first had the machine from January to February 1952.  So the little beast has some sentimental value to the family.

The engine and petrol tank were stored for many years, the cycle having been discarded, when I graduated to 500cc Triumphs.  The down tube mountings were the only parts to go missing in the intervening 34 years, although the front number plate did go AWOL in the potting shed for a while.

My father manufactured a new down tube mounting in stainless steel and is currently sleeving the decompressor arm mounting in the cylinder head, but he is totally stumped on how a new roller could be built should the old one fail or even on how to test the cracks to see how much life is left.  This type of failure might be the reason why so few Mosquitos are reported as active in the club.  Or is it failure of the fibre driving gear?  This one stripped its teeth many years ago, fortunately while spares were still available.  Or is it the difficulty of obtaining ignition parts?  I managed to obtain a replacement HT pickup from a source in Holland, although we had to resort to machining the acorn from Tufnel.  Fortunately the thread is 14mm so a spark plug tap was pressed into service to cut the thread.

Information and requests for help welcomed!

[The problem of cracking die-castings is one that is familiar to collectors of old toys and it often occurs in the wheels Hornby trains.  It is caused by impurities in the metal - usually when surplus metal was put back into the melting pot.  The solution adopted by toy train collectors is to allow Superglue to soak into the cracks, but would this method be strong enough for the Mosquito? - Editor]

First published - August 1997

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