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Bike Review - Posted 1st November 2013
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Royal Enfield 500 Twin

Back in the day, Colin Evans enjoyed some entertaining experiences with an early Enfield 500 twin. Just how did the final drive chain end up in the oil tank?...

My 500 Twin was bought from Messrs Cyril Morgan of Caerphilly in April 1951. I was looking for a replacement for my Model G and there in the window, taking pride of place, was this stunning-looking bike. Silver and chrome tank, black frame, guards, etc. Funny thing; I've seen a few others in battleship grey like the Bullets of that era (which the Twin closely resembled, apart from the engine), but never in black.

I just had to have it. If my memory serves me right it cost around 219.

What a lovely little bike. Very pleasant to ride, a soft engine with 6.5:1 compression and a published top speed of 86mph. It felt a bit of a pogo-stick on bumpy bends though, with its own make rear shocks. Nobody thought of fitting Girlings or something in those days, but Enfield went over to Armstrong units later.

Built like a gun...

It seized up once doing about 70mph past the Beacons reservoir on the A470. Fortunately a very nice RAC patrol man soon had me going again, after letting it cool down for a while and rocking it backwards and forwards to loosen things up. At the time I thought it was the pistons picking up in the bores, but was to find the cause later.

I had to take the Twin down to Bradford on Avon, where the engines (and lawn mowers) were manufactured, to have pinch bolts fitted to the crankcase between the separate cylinders. This was to cure an oil leak from between the crankcase halves, which were swimming in oil around the dynamo area. It leaked from day one but in my naivety I thought that the dealers had over-filled the oil tank, talk about wet behind the ears! Joe Public was the test rider in those days.

When the engine was stripped down to do this work, it was found to have heavy big-end scoring. Presumably that was the cause of the engine tightening up and I was advised to have a service crankshaft ground under-size, off the shelf together with under-size rods of course. The trouble there was possibly my fault as I might have neglected to change the cork oil seal on the quill transfer pipe between oil pump and crank shaft at oil change. Or did it split when under the extra oil pressure at a higher speed? We shall never know, but Enfields did fit neoprene oil seals later, I believe.

All this was starting to get expensive and I had to bear the cost. There was no mention of warranty liability on either job. Did I mention I might have been a bit wet behind the ears?

Colin's bike, as it was originally...
Enfield Bits on Now...

While this work was going on I asked if I could look around the factory. A smart gentleman in a pin-striped suit agreed to escort me around the site. All very interesting; with drilling machines and camshaft grinders vibrating their way through the wooden floor. Outside the main building, past hundreds of crankshafts weathering and waiting to be machined (some even waiting to be machined undersize perhaps), we came to a small (noisy) building where about half a dozen engines were being run with their exhaust pipes poking out through the wall.

My guide informed me that these were their new experimental engines under test, all a bit hush-hush at the moment. I was told that they were using 350 Bullet rods and pistons with shell bearings. and cylinders to suit. My guide also said that as they were using the 500 Twin crankcases, there was such a small clearance between rods and case that if a big end gave trouble, you'd probably hear the rods hitting the case before anything else! If and when it went into production then they would obviously have to cast new cases. This was the start of the 700 Meteor and became a talking point back at the bike club for a while.

COuld happen to anyone...

Another thing that happened with my 500 (and could happen to any other 500 Twin of course) was late one night, coming home from the bike club. My mate Hubert Griffiths was on the back when there was a big bang and sudden loss of forward movement. We soon realised that the rear chain had gone AWOL. So Hubert went back down the road to look for it, without success. We were kindly towed home by another member on a Bullet. He was an upholsterer by trade and just happened to have roll of webbing in his pocket which was tied to his machine. The other end was wound around my handlebars, with me clutching the end which I could release if things got 'out of hand'

In the cold light of day, I found the chain - in the oil tank! This was the rear part of the crankcase casting, similar to that on the Bullet. Trouble was, that if the chain broke, there was so little clearance between the gearbox sprocket and raised parts of the crankcase casting to accommodate the through-bolts that a pile-up was practically inevitable. In my case, it duly punched a two-inch hole in the oil tank and just about disappeared inside. We had some good aluminium welders at BOAC Engine Overhaul where I worked, so had it expertly patched in no time. After a speedy strip-down, the Twin was all up and running again in just a couple of days - I had to have the bike to get to work, see!

A world wide reputation for reliability...

Timing chain noise was a constant problem, adjusted by moving a jockey-wheel on a moveable quadrant. I never got it to run quietly, and was told many years later that there was a trick way of doing it, something to do with turning the quadrant one way then another. Don't ask, I was baffled. The chain drive to the dynamo by the way, was non-adjustable.

I part-exchanged the Twin in 1954 to buy a 350 Gold Star, when it still looked good. The next time I saw that bike only a couple of years later, it was leaning up against a garage in Cardiff, looking a sorry mess. Why do people do this? I could have cried.

Taking a short run on my son's Meteor Minor was completely different. It's a much more buzzy engine and not a bit like the steam-engine qualities of the 500 Twin. Good brakes though.

Colin's bike, as it was originally...

The photo above shows my machine with its aftermarket twin-seat is from Feridax. The seat on the bike when new was a single Lycett sprung saddle, with no pillion perch to discourage customers from carrying passengers while running in!

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