Lightweight Leanings (or how I came to appreciate a much derided
model) (2005)
Although I have been interested in motorcycles since my early years I have never been “marque specific” in my interest and have never really understood devotion to a particular make (or even nationality) of motorcycle to the exclusion of all others despite whatever merits another might have. As such I was not exactly a likely candidate to join the ranks of a “one make” club such as the AJS&MOC. After all, I had never owned an AJS or Matchless. In the early to mid sixties when I was young and just starting motorcycling, they were generally considered “old men’s bikes” by those I tended to associate with, so I never wanted one and when I got older, well, one just never turned up in my garage from the many swaps and acquisitions which just happened over the years.
This omission in my motorcycling life changed at the end of 1993 when I advertised in Old Bike Mart that I wished to swap my Land Rover for any 1950s/60s single cylinder motorcycle of 350cc or over which was in a reliable running condition (I wasn’t too worried about the cosmetics) and what turned up was a Matchless G5 350cc lightweight. Quite coincidently, about the same time I met Kevin O’Brien, who said that I ought to come along to our local AJS&MOC section meeting as they were a good crowd as well as being a local club to me. At that time the meetings were being held at “The Drill House” pub out back of Stanford Rivers which was only about seven miles from my home.
Now I had often read disparaging remarks about the AMC lightweights from AMC guru Frank Westworth and other journalists in magazine articles of that time and soon found from the club magazine that such views were generally reflected within the main AJS & Matchless club as a whole, with the Jampot magazine rarely mentioning lightweights and if it did then usually with a derogatory comment following, or in the various letters from members, which incidently often reflected their ignorance of the model in that they often referred to it as unit construction (which it certainly isn’t). It appeared to me the club was seemingly totally committed to what appeared to be just two models, heavyweight singles and twins. Even the spares scheme seemed to pay only token service to the lightweight models. First impressions of the National club were not encouraging and just seemed to confirm all what I had suspected about “one make” clubs in general.
Fortunately this was not true of
our local East London and
My 1960 G5 Matchless when I first saw it
One difference with my bike though was that it was (is) a “bitsa” in that it is fitted with a complete front forks wheel and headlamp from a heavyweight bike, which means that it has a 19 inch front wheel and the full 7 inch front brake. With a 3.00 front tyre fitted instead of a 3.25, to keep the overall diameter roughly the same as the original, it not only handles really well, but stops well enough for 350 performance as well (not too sure how I would feel about the same brake with a 650 CSR twin though!). I know that the James/AMC type forks as fitted to earlier 250s are not well thought of and I have to agree, from experience with my own Francis Barnett (which also used them), although they work well enough when in good condition and are a darn sight better than the forks which BSA fitted to its Bantam or the undamped Metal Profiles forks which were fitted to many other lightweight bikes of the time. Their pressed steel construction makes them an absolute pain in the backside to work on – or indeed to fit to the bike unless you have at least three hands. Also the British Hub Company’s 6 inch front brake which went with them did not exactly cause the tarmac to melt when used hard. So I was glad that my bike did not have them and “to Hell” with originality. Another thing I thought was better about the complete heavyweight front end of my bike was the larger headlight unit and speedometer. All in the mind and an optical illusion I suppose but they seemed to make the bike feel bigger than the standard lightweight bike with its smaller headlight unit and it no longer feels like just a slightly larger capacity version of the 250. I think that AMC might have had better sales of the 350 if they had made them like my one, but I suppose costs came first.
I suppose that over the years I have become known in the section for being a “lightweight” enthusiast and I have come to know quite a lot about them. However most of my knowledge is not of the “hands on” type, because I have never had to do any work to the engine or the cycle parts so far. Up until I took it “off the road” a couple of years back I was clocking up about 1500 miles each year on my G5 and apart from general checking and lubrication all I needed to do was change a worn carburettor slide and clean the contact breakers occasionally. It never gave me any trouble, so I was not going to upset it by taking anything apart. A pity that I could not say the same about the transmission though, as I have been inside the gearbox three times now trying to fix a problem. This first manifested itself on the way back from the 1996 Mersea Island Jampot Rally, when it became obvious that the rumbling from the gearbox was definitely getting worse, as was the oil leak from the final drive sprocket.
The heavyweight “front end” fitted to my G5
After much poring over the manual and “Classic Mechanics” articles on a lightweight rebuild, written by Bill Redford, I tentatively delved inside the box, after carefully decanting its three pints of oil on to the garage floor when the cylindrical box rolled over while I was not looking, leaving the clutch cable exit hole at the bottom, instead of the top, where I had left it in order to prevent just such a thing happening. Is there any other bike where the gearbox holds more oil than does the engine oil tank? I doubt it (the engine holds two and a half pints). It’s truly amazing just how far that much oil can spread on a concrete floor, still at least the concrete will not go rusty now. However, the advantage of such a large gearbox casing is that there is quite a bit of room to get fingers inside when needed, so it was not too difficult to locate the worn bearings at each end of the main shaft and change them, along with the final drive oil seal. All bolted back together and in the frame, I found that I could not select any gears – The quadrant had moved as I pushed the outer case home and I had been daft enough not to try the selection again for the final time before putting it back in the bike. All apart again and another three pints of oil drained out (into a can this time) to sort out this little oversight and this time it all worked well.
All went well for a year or two, but then the final drive oil leak started again and there were also still rumblings from the gearbox, although the gearchange was absolutely fine – In fact it was superb. I took off the primary chaincase once more and saw that the clutch seemed to be moving “out of true”. It must be the mainshaft bent, I thought. So it all came apart again and although I could see nothing wrong with the shaft fitted I ordered a new one from Russell Motors, along with yet more bearings. All rebuilt once more and back in the bike it still seemed just like it always had. It still ran very well and the gearchange excellent. In another year or so though the final drive oil leak started yet again. With so much oil in these boxes this can always be a problem anyway, because the final drive oil seal is constantly flooded with oil, but this one gradually got worse and worse until it started lubricating the rear tyre, so when I took off the primary chaincase again and saw that the clutch was still moving out of true I had a brainstorm and assumed that my gearbox must have been built up by a previous owner out of mismatched parts and that the mainshaft was running out of true in the box itself. At the 2003 VMCC Founders Day I saw a lightweight gearbox for sale in the autojumble and bought it for rebuild. In the mean time I continued to make my oily way around on the G5, always looking for grass or gravel to park it on to save me from too much embarrassment.
The new gearbox turned out to be in quite good condition, but it had a later mainshaft, as used on the later 250 CSR models, fitted. This meant that I either had to buy yet another mainshaft from Russells, or try getting a new clutch centre – or indeed a complete clutch. I decided to go for yet another new mainshaft and subsequently built up the new gearbox complete with a new 18t standard size gearbox sprocket. It was now all ready to change over – but that is how it stayed for over two years for reasons that I am not really sure about other than that I was playing around with other bikes at the time. Ever so often I would look at the gearbox on the shelf, move it to get at something else, or try to hide it so that I wouldn’t have to think about having to fit it sometime, but it still did not get done despite section members ever so often asking me about what had happened to my bike. Then all of a sudden, a few weeks ago I was looking at my rather sorry looking G5, all dust and alloy corrosion, in the garage and had a massive twinge of conscience.
With the petrol tank now resplendent with shiny new (chrome plated metal this time) badges which I had bought about a year ago on went the replacement gearbox. It was at this stage I noticed that the clutch was still running out of true – in fact it was running eccentrically. Being that all the component parts seem as they should be I can only assume that it has always been like that. In fact all my gearbox problems seem to have been caused by the fact that with the clutch running as it is there is quite a difference in primary chain tension at different rotational positions of the clutch unit. I had probably set the primary chain tension at one of its slack points, which was then tearing the gearbox bearings to pieces on what must have been the extremely tight points. I now know that I had made a wrong decision in getting another mainshaft instead of another clutch centre spider and that eventually I am going to have to do something about it. But for now, it has fired up and run and with the primary chain now adjusted to be right at the tightest point. I will probably eventually get around to fitting a new clutch centre spider but before I do anything else to it I will just use it and see how it lasts this time and while it runs OK the clutch centre change will have to await its turn amongst work on my other bikes. One annoyance though was that when I came to put the rear chain back on I found that it hung in a great loop. It turns out that my other gearbox sprocket was not the standard 18T which I thought (and had bought) but the alternative 20T part. My gearing has now been effectively lowered by quite a bit and being that I was happy with it as it was I will probably now find that the bike seems to be over-revving at the 50-55mph gait I usually run it at. Oh well! AMC might have selected that gearing for maximum speed with a high revving engine but I prefer the more leisurely feel of a lower revving engine, so we will see how it goes.
(2022 update)
Well I was right about thinking that I would not like it so much with that 18tooth sprocket and very quickly reverted to the 20tooth one. Since then the bike has given me 17 years of mostly reliable use. That clutch centre part was unavailable I found and when the club spares scheme had some made at last I bought one ready for changeover when needed. However, it still seems to be running fine as it is and indeed the G5 has become my regular winter riding bike because it is the easiest of my bikes to keep fairly clean from too much winter muck due to its smooth engine shape and the undertray type frame bottom which makes it easy to wipe down with an oily rag. Indeed that is the only cosmetic treatment that it does get. I did treat it to a new Monobloc carb a couple of years back when the old one started playing up and then jamming so the bike was off the road for a while until I got that sorted, but that is about all I have needed to do to it other than fit a couple of new tyres and sparking plugs. It is no glamour machine and I have to say that despite the oily rag treatment it does now have more rust on it than it did when I wrote the first part of this article. As it is not my only bike it still only does about the same sort of mileage as previously stated each year, but that has added up to quite a lot over the years I have had it (can’t say how much for certain as although the speedo is fine the odometer has never worked). I still enjoy riding it as much now as I always have done and that 20 tooth sprocket in my view gives it a quite relaxed feeling bike at my usual 50-55mph cruising speed. Pristine it’s not but it certainly it is going to be a fixture in my garage for as long as I am still able to ride it.