Clews Competition Motorcycles began business by buying excess B50 parts from BSA when they shut down. These engines were bored out, fitted with bigger valves, carbs and chucked into a very neat frame. They did this for a few years until the engine couldn't be developed any further, adding four valve heads, improving the clutch, making a stronger three speed gearbox and improving frame and suspension. End of history lesson, time for strip down.
Removal of engine was simple, three bolts, rear chain, oil and petrol pipes then lift out. The only special tool needed for the strip was a clutch hub extractor. I noticed that the con-rod had heat discolouration marks - the rod was bent and an unsuccessful attempt had been made to straighten it. The cost of a new CCM rod, big-end journal and bearing was £108 from OTJ. I learnt from them that B50 rods had a habit of bending when they got bored with going up and down. The CCM rods are much stronger, thankfully.
Cleaning the sludge trap in the crank I found bits of metal. The timing side crank mainshaft had a deep groove where the oil seals run. I couldn't find a new mainshaft, so I had the groove turned off and a bush press-fitted onto the shaft. A word of warning, pressing the shafts in and out of their respective flywheels, required the use of a 25 ton jack, more normally employed for lifting derailed locomotives. The con-rod fitted, the flywheels were trued up, the new journal nuts loctited and tightened to 160lbs/foot, then the flywheel again checked for alignment. Three new main bearings were fitted, the crankcases bolted up, and Sheila’s your Aunty, one free spinning crank and rod.
With a new set of rings (expensive) the rest of the engine was in good shape, except for the gearbox. This had led a hard life and the four speeder wasn't so butch as the CCM box. Chipped and cracked gears were replaced and the kickstart mechanism reinstalled as I didn't fancy trying to bump start the beast if it stalled in traffic. This got rid of £109, as used parts are rarer than bits for Gold Stars. I took care with the shims and ended up with a smooth gearbox.
A new clutch, alternator and timing side case (instead of the CCM item as it didn't have a hole for the kickstart) added to the new bits. I had to relocate the footrests on the end of one of the engine mounting bolts, as the new timing case didn't work with the old pegs. The frame was cleaned out as it carries the engine oil, the filter in the bottom of the front down tube was eventually removed for cleaning after mucho swearing. The magnesium hub in the rear wheel was cracked and replaced with a conical Triumph item. A pair of new Hagon gas shocks fitted on the rear and the Ceriannis out front were straightened. The front wheel was replaced by a used XT250 job that came with a speedo.
Electrics were uprated in the space emptied by use of a K&N air filter. New battery, rectifier, zener diode, ignition coil. Mudguards, side panels, headlamp, etc came from a Kawasaki KX, all in lime green - not so clever an idea in retrospect as spotty kids keep asking me if it’s a Kawasaki 125 and urge me to do a wheelie. The alloy tank looked like it had been run over by a steamroller, but the worst of the dents were knocked out and the inside filled with GRP resin to fill the cracks and stop the leaks.
The moment of truth came when it was all back together. Tickle carb, ignition on and leap in the air... the lever stuck halfway down its stroke and wouldn't move. Turned out they'd sold me a 250 BSA quadrant which has the centre of the gear at a different distance to the 500. With the correct part fitted I was back in business.
I always thought that tales of people being put into orbit when a big single kicked back were a bit far-fetched. But as my shin made contact with handlebars, crushing an unprotected thumb, I saw some truth in the fables. I got off the bike and took a swing with my right foot... at the rear tyre (I'd learned from past experience to kick the soft parts) but the bike had the last laugh as it toppled off the milk crate. I dived to catch it, hitting my head on an innocent shelf. Some people are a danger to themselves.
After recovering, I made another attempt. This time I let my leg go limp as soon as I kicked down. This way, any kick-back made my knee bend, stopping just to the side of my chin. After a few kicks, BLAT, BLAT for 15 seconds then FUTT. Adjust tickover screw, kick again and a steady roar until I switched off.
A quick check over, helmet on, start up, no scruffers about, into gear and then illegally up and down the street a few times. The bike and horizon shook and juddered, but began to smooth out as revs rose. After checking to see if the wheels had turned square, I returned to the garfige. The exhaust was clean, the lights worked, but the brakes seemed a bit vague - need time to bed in, I thought, recalling that CCM sales literature had said the engine braking was strong enough to use as a third brake. My dad came out of the house to complain that it sounded like a berserk dumper truck; I thought it was more like a frenzied pile driver.
After a lot of hassle proving the bike's age, which included a visit to CCM’s headquarters (the bike turned out to be an early factory racer issued to Jim Aird), I managed to extract an M registration from the authorities. Of course, you can't have the registration until you get the MOT and you can't get the MOT unless you have your registration to ride to the testing station. Thank god for my father's van. It failed on a minor point, but | went to the garage next door where it passed!
I took great care running it in for 1500 miles - after all, all those new bits had cost lots of dosh. I avoided any rough stuff or large throttle openings. Up to 50mph it appeared quite smooth, although at low revs it really shook about par for the course for a big single without any balance shafts. I even began to master the kickstarting. The first time in the rough was a disaster. The chain kept jumping off the sprockets. Luckily, it only came off on the rear one - access to the engine sprocket meant removal of engine cases and a clutch stripdown. Hardly much fun out in the rough. The problem was solved by packing out the chain tensioner with a thick bit of rubber. Chain adjustment is, by the way, simple, as there are snail cams at the swinging arm pivot.
Whilst thrashing in the mud, oil came from the frame breather, positioned just behind the headstock, exiting through a pipe just under my left foot. This was cured by filling the frame with oil until it was just visible in the top frame tube. The primary chaincase shares the engine oil, but the gearbox oil seeped in and out - sometimes the gearbox was overfull, sometimes nearly empty. Oil was also coming out of the gear change shaft at an alarming rate (true character).
I thought the worst. Which is a good way of thinking when owning a British bike. If you are pessimistic, things can only be as bad as your worst fears, then if after investigation things aren't as bad as expected you can celebrate.
The tidal effect of the gearbox’s oil level was caused by three holes drilled through the inner timing cover, and one through the gearbox. Thus crankshaft pressure added and subtracted oil from the gearbox. Its oil breather pipe had been crimped shut. The holes were tapped and plugged. I had an aluminium ring welded around the gear change shaft boss on the outer cover. I then milled a recess and fitted a standard half inch seal. An O-ring seal was fitted to the shaft, as an additional seal to the inside timing cover. Overkill? Well, Id been using gearbox oil at half a pint every 30 miles, and it only holds three quarters of a pint.
The forks appeared a bit soft, so were filled with 10/30 oil, making them a bit firmer and stopping them bouncing back against the stops. Back on the pit heaps things were looking good. The oil stayed in the gearbox, the chain didn't leap off, only the firmness of the shocks was spoiling the fun. I repositioned the shocks, after making some plates, just forward of the back wheel axle, some six inches further back than stock. They're still a bit stiff but much more usable in their laid-down position.
One day, I was going as fast as I could across one of the fields when I spotted a car pulling a trailer with a new Honda CR500 aboard. The driver got out, put on his full suit of body armour. He started the bike and rode the same circuit I'd just taken in ten seconds - it had taken me ten minutes! Approaching the muddy fields at speed, he would raise the front wheel and ride through on the back wheel. I turned the same shade as my bike in envy.
Anybody can do that, I thought. Off I headed in line for the puddle, the front wheel wouldn't lift up and as the bike hit the water there was a cloud of steam, the bike rattle-snaked from side to side... l kicked down to keep upright, nearly leaving my size nine in the mud, complete with leg; then the engine died. It wouldn't start for a few minutes. After much swearing she roared into life and I shot off around the bend that turned sharp left, up hill and along the aforementioned embankment. I went sideways straight off the top and down the other side, following the bike into the nettles. Hearing laughter from some spectators, I got up pronto and went home hurt and fed up.
A series of electrical faults followed, usually loose bullet or spade connectors. The points needed adjusting every 800 miles. Left untouched, the engine tumed vicious and kicked back heartily. Water was always finding its way into the point's chamber until a combination of silicone grease and a cork gasket were applied. Then, sometimes, the points would oil up. As I'd already fitted a new seal and the shaft looked perfect, there wasnt much else | could do, apart from fit a breather which would let in the water again.
The last straw was when the battery jumped out of its holder and took to arc welding as a hobby. The negative terminal was still earthed whilst the positive had vaporized itself against the frame, resulting in a long push home on an extremely hot day. | bought a £55 electronic ignition unit from OTJ and fitted a big capacitor instead of a battery. I had to buy a positive earth rectifier to work with the electronic ignition and narrowly avoided meltdown of the zener diode as Id forgotten that it needed a much bigger heat sink as all the excess energy was chucked into it, instead of the battery. The lights won't work at tickover speed without robbing all the juice from the engine.
One morning when I kicked the engine over there was a squeak from the kickstart and the engine wouldn't go past compression. A sheared key in the gearbox mainshaft caused the problem, this was renewed and the bike then did over 5000 miles free of trouble, save for the rear tyres. A motocross knobbly was eaten up in just 1500 miles. A Metzeler Enduro lets you put your ear on the tarmac when cornering and even grips well in the wet when braking. On the dirt it clogs instantly, giving no traction even on dry shale or dry earth and is as much use as a chocolate fire guard. I shall be returning to knobblies when this one wears out.
The bike-handles as well as I could wish on the road. It seems a bit top heavy in comers but this doesn't affect stability. I weighed the bike in work - 260lbs including oil and a gallon of petrol. The new four stroke KTM has a dry weight of 261lbs. 15 years of progress hasn't shown much change, but I suppose power has gone up. The CCM can do very impressive power slides in any gear or at any speed in the dirt. It's just a question of throwing the bike over as hard and as far as you dare, then whacking open the throttle, keeping the outside peg weighted and body weight forward. My favourite game.
The bike does a wheelie by either dropping the clutch with a few revs wound on or by giving a gentle tug on the handlebars, opening the throttle simultaneously. I prefer the latter as | hope it saves the transmission from heavy shock loadings. | learned the latter accidentally, in front of several spectators, when after the engine had stalled and I'd cleaned the oil off the points, it began to splutter, so I gave it a handful of throttle, forgetting that it was a quick action twist grip. The engine picked up and hoisted the front wheel into the air. I scooted down the pavement on the back wheel, onto the road, out of control into heavy traffic and was the first person to do a stunt combining body popping with riding a motorcycle.
Removal of the baffle totally changed the engine characteristics. it changed from an engine that pulled hard up to the middle of the rev range and then ran out of torque, to one that was gutless until the halfway point when all hell broke loose, the back wheel started to spin, the bike weaved and the thing sounded like some furious monster. I had to stop very quickly to avoid going off the field into a quarry.
The acceleration was quite breath taking sans baffle, top speed somewhere between 95 and 105mph (the Yam’s clock stops at 60mph). I was stopped by the police over the noise, but told him it was an old bike and they always sounded that loud. He admitted he was confused by the noise regs, so let me off with a document check. The bike averages 35mpg under hard use and you have to add a pint of oil every 200 miles. The chain is due for renewal after 5600 miles, but it was only a cheapie.
The bike has cost me £800 in bits to get to its current state and a lot of hard work (which later included replacing the footrest brackets with alloy items welded to the engine cases, after the former bent miles from nowhere). It's a tough beast, hard to break on the dirt and great fun to ride. It accelerates as rapidly as my friend’s well tuned Harley Sportster up to 50mph. Excellent in the traffic light GP, provided you can keep the front wheel on the ground. The bad points are high consumption of consumables (especially liquid ones) and the underpowered front brake. I'm selling the bike as I want one of the new CCMs or a KTM.
Adam Lynam