TRIUMPH TERRIER TWO
Last time, Terrier and Tiger Cub expert Mike Estall had resolved various teething troubles with his 1956 T15. So it was now ready to ride off into the sunset, yes? Well, we all know how that turns out…
Last time, Terrier and Tiger Cub expert Mike Estall had resolved various teething troubles with his 1956 T15. So it was now ready to ride off into the sunset, yes? Well, we all know how that turns out…
Once it was back on the road, I played with the carburettor and ignition timings until the T15 was running the way I liked it. Unlike the later, side-points Cubs, the T15’s distributor and external clamp made ignition timing adjustments really easy. However, I noticed smoke coming out of the kickstart bush, indicating that combustion products were getting past the piston rings and building up crankcase pressure.
Compression became poor and starting difficult. After a year some engine work became necessary, so oils were drained and the unit was taken out of the frame and made ready on the bench. The first job was to remove the cylinder head. I had not built this engine myself and this would be the first time I had been inside it. The cylinder head was firmly stuck down. All the nuts came off OK but the head could not be lifted. It would not come past the front drive-side stud thread. After many hours of levering and wedging it still would not lift and I managed to break the top barrel fin as well. Damn!
Whoever had built the engine before the Gaffer’s Gallop re-run had not fitted all the washers under the cylinder head nuts. Tightening the nuts had crushed the alloy head material onto the stud threads, making it completely immovable. One side eventually yielded to persuasion, but I had to use a hacksaw blade between two fins to laboriously cut through the high-tensile steel barrel stud on the other. This left the top half of the remaining stud firmly jammed in the head and the other half still in the crankcase!
The half stud stuck in the head had to be drifted out and the half stud in the crankcase was removed with an extractor. Then all the cylinder head stud holes were drilled out to 21/64”, their original size, so the head could eventually be refitted.
Part of the top barrel fin broke, so the remnant was cleaned up and glued back on with a bracing piece, high temperature adhesive and crocodile clips. A couple of coats of high temperature silver finished the invisible mending job.
Further stripping showed the drive-side mainshaft rotor key had sustained some damage and the rotor keyway too, allowing the rotor to wobble on the drive shaft. I turned the rotor around (with the ‘Lucas’ logo facing inwards), so the damaged part of its keyway was not in use. There had been some minor clonking and this may well have been the cause. I also fitted a new Sparx encapsulated stator.
I tried making an extended rotor key but my engineering skills were inadequate, so I employed a little sideways thinking and used a
new key to sit in the rotor adapter slot. This sat too low, so I made another flat key that sat inside the adapter slot and protruded outwards to connect into the rotor itself. So now there were two keys: the existing Woodruff key held the rotor adapter to the engine mainshaft and the other one connected the adapter to the rotor itself.
The timing-side flywheel sludge trap was about half full, was cleared and the oilways flushed. Then came a real shock. The thousand-plus miles I had ridden, including several trips of sixty miles or more, had been accomplished with no oil pressure whatever! How do I know this? Because the oilway plug at the centre of the timing-side flywheel was missing, absent, not there and never had been!
The only oil to the big end had come from crankcase oil mist and centrifugal force of oil from the pump feed, most of which would have gone straight into the crankcase and not into the big end at all. Even so the roller big end had survived. There was no debris in the crankcase, oil filter or sludge trap so whoever built the flywheel assembly must have had an off-moment…
The Alpha roller big end, although still in very good nick, was replaced with a brand new plain big end assembly from my spares stock. I pressed the new crankpin into the timing-side flywheel, ensuring the oilways in the flywheel and pin lined up. I blocked up the thread into the timing-side main bush journal and filled the sludge trap with oil – which immediately flowed out of the big end journal, proving that the oil feed was sound:l.
Having stripped the flywheel assembly, it was time to do some measuring. I found some wear on the timing side main bearing journal so the flywheel was centred in my lathe using a 4-jaw chuck and dial gauge. The journal was then very carefully machined down until it was concentric with the flywheel edge and the same diameter all along its length. A new -0.020” undersize timing-side bush was then fitted into the crankcase.
However, my very careful machining of the flywheel journal had not been careful enough and I had reduced the diameter of the stub to slightly less than the fitted bore of the brand new bush. There was a little bit of slack. ‘Oh dear,’ said I. ‘What a nuisance…’
Some thinking-cap time and another bucket of tea provided the answer. Let’s see
what fteeler gauge could be introduced
between the bush and the journal. With the journal pushed right over to one side a 0.002” thou feeler would go in the gap but a 0.003” would not. OK, so the gap was roughly 0.0025”, which equals 0.00125” all around. An oil film is about 0.0005” to 0.001” thick so the actual degree of slack was quite acceptable. Hurrah!
The piston rings were in poor condition and the small end bush was also worn. The top piston ring was partly stuck in the groove and the second ring mostly stuck – this is where compression had gone. The piston was +0.020” and measured up OK so it was used again with new rings. The bore was undamaged and was just deglazed.
Poor lubrication to the small end on these machines has always bugged me. On every Cub / Terrier I ever owned the bush had always worn pretty quickly. There was no direct oil feed, only lubrication by crankcase oil mist. This was witnessed by the adjustable reamer I bought in 1957 to ream the small end on my first ever Cub and which has been in regular use ever since!
I decided to improve oil access to the small end bush by drilling two 2.5mm holes through the underside of the conrod eye, so that oil mist might be encouraged to enter on both the downward and upward strokes. The holes were rounded off to try and relieve any stress points.
On a previous bike I tried to reduce the wear of the small end bush by installing a needle roller bearing. A proprietary bearing was found and the conrod eye machined to fit, but there was a slight wobble when the gudgeon pin was inserted, indicating a thou or two of slop. When the bike was run this slop could be heard, particularly on the overrun. When stripped the small end eye had been blued by the heat generated! Another good idea come to nothing…...
When I’d removed the piston I found that a ‘looped’ type piston circlip had been used on one side and an original plain-ended wire type on the other. The looped type are easier to fit and remove than the original, whose ends sit down in the groove and are difficult to prise out. However the two circlips used had different diameter. The original and correct plain-ended circlips had a wire diameter of 0.039” (#2 from the left in the photo) and the other circlip used was 0.047” diameter. That circlip would sit proud of its groove, with the possibility of it coming out and allowing the gudgeon pin to slide out as well. This is not a good thing!
I found various other circlips and would suggest that any reader check carefully if he decides not to use the original, plain-ended circlip type. One type found was a flat oblong in section with squared sides, and there was no way this type would sit properly in the round circlip groove, and so must not be used. I used two loop-ended type of the correct 0.039” diameter.
The valves, guides and springs were checked, found to be OK and the valves given a light regrind. The sparking plug hole had been helicoiled but the lower part of the coil protruded into the hemisphere, possibly causing a hot spot, so it was carefully ground flat.
The inner drive-side cover was a very early one and was devoid of any oil seal for the gearbox mainshaft.
Many years earlier I made a 3-way cutter to modify early covers like these enabling the use of a proper garter seal. The later Triumph rubber ‘labyrinth’ type wore very quickly so I never used them. The first part of the cutter fitted the existing hole in the cover, acting as
a pilot. The first cutter widens the same hole to accept the width of a longer phosphor bronze high gear bush not previously fitted. The second cutter cuts the dish for the garter seal and the top cutter does the outer diameter for the clutch seal cover.
I’d also made press tools to manufacture clutch seal covers from the end caps of baked bean tins. Another satisfying bodge!
The original gearbox mainshaft had been damaged by heat, with evidence of blueing so the mainshaft and gear cluster was replaced. I also found an old high gear so the long bush was pressed out and turned around making a good outer surface for the new clutch garter seal to work on.
The gearbox sprocket nut was loose on its thread because it had not been centrepunched when the engine was built. The original, felt, high gear oil seal was leaking so I made a new one, but also backed it up with a semi-sealed 6205 bearing.
When it came to rebuilding the gearbox, things did not go well. The drive-side inner cover sat about 1/8” proud and would not go down properly. I had lost one of the dowels and made another, but I discovered it was about 1/8” too long, so it was shortened to its correct length. The cover then seated properly, but the gear quadrant and selector would not locate and I could not get the camplate pivot pin into place.
After several attempts, several cups of tea and much head scratching I finally decided to read the instructions in the manual. I have built a lot of Cub and Terrier engines in the past. I did not usually need to refer to The Book as it was all in my head and I had lots of experience to call upon. The book reminded me that the mainshaft second gear has two grooves, one either side of the gear itself. There was a thick groove for the selector fork and a thin one, but the gear could be placed on the shaft either way round. And, yes, I had put it the wrong way round! Stupid or what?
Once the gear was located correctly the cover dropped neatly into place and all was well with the world. Much time wasted…
The gear indicator had stopped working. Not that I needed one (after nearly sixty years riding Cubs and Terriers I can remember where and in what order the gears were set!) but it was on the nacelle and I thought it should at least be functional. Examination showed that the gear indicator control rod had become severely bent, so I fitted a new rod and put a reinforcing tube around it. The material used was a nice bit of stainless steel tube from an old car aerial. Never throw anything away.
All engine threads were cleaned out and re-tapped and dies run down all the other fixings. Also a new primary chain came out of its packet. ►
The central screw holding the timingside inner cover to the crankcase body was broken and the broken half was still buried in the crankcase. Not only that but there was a very large hole where only a 2BA thread should be. I drilled out the broken screw from both sides and got rid of the remains. JB Weld came to the rescue, filling the hole, and the thread was re-tapped.
The rocker covers were distorted where the nuts had been done up too tightly in an attempt to make them seal better. This distorts the cover even more and only makes matters worse. So they were made flat, first using a file then a surface plate with wet and dry paper.
The rebuilt flywheel assembly was checked on my home-made jig, whacked where necessary with a copper mallet and, when true, put into the crankcase. Would it rotate using just finger and thumb and without any binding? Yes, so everything was properly lined up.
I always use my lathe to prime and check the lubrication system. A metal and rubber tube connects the lathe chuck to a turned-down primary sprocket, which picks up the drive-side mainshaft splines, and the lathe runs at very low speed. Keep oil in the plastic funnel until the scavenge side kicks in and squirts returned oil into the red hair spray lid underneath. My wife donated the hair spray lid.
The petrol tap had been leaking. I’d fitted a pattern tap but later found the bottom thread was too short, so the union nut could not tighten properly. A fibre washer soon had that fixed.
Then came the Great Day. The day when the spanners were put aside, battery connected, oils loaded and the engine was to be started for the first time in over a year. A light flood of the carb and the first kick: nothing. A bit more flood and another kick: phut. A bit more throttle: almost. Fourth kick: BRAVO!
It ran nicely at tickover and picked up on the throttle too. The was very pleasing and I gave myself the pat on the back. After running at tickover for a few minutes, during which time the oil return was checked, it was time to don the helmet, put on the gloves and go for a short ride.
Very short! All the self-congratulation dissolved into thin air when, after about 200 yards, the motor just stopped. Kickstarting attempts showed that compression seemed to have completely disappeared. The bike was still in gear and yet could be pushed with absolutely no resistance at all from the engine department. Odd. Very odd. I pushed it back home, while embarrassment, worry and annoyance ruled in equal measure. I was in shock. Play was temporarily suspended and another bucket of tea consumed.
With the bike on the ramp things looked even more peculiar. The rocker covers were removed to find both valves apparently stuck part open – hence no compression. But why? I tried using the kickstarter but it did not rotate the engine. What was going on?
Time to remove the cylinder head and dig deeper. As the head was gently prised upwards the valves began to drop onto their seats. So at least they were not stuck open. The mystery deepened!
Neither tappet was down at its rest position, but both were sort of half-way up… or down. As one tappet was pushed down a few millimetres or so the other one rose by the same amount. Very weird! The mystery was deepening and I was getting very worried. Time for another bucket of tea. Think on it overnight.
The next day the mystery was investigated, and as the inner timing side cover was pulled away it became immediately apparent what was wrong. Some fool (me? I don’t believe it), had not tightened the timing pinion bolt which pushes the pinion onto its taper, so the pinion and bolt were both loose. And just
to prove the point, the bolt head had made a witness mark on the inside surface of the inner cover while trying to escape!
At the same time the timing pinion had come off its taper and made a valiant bid for freedom. This didn’t happen while the engine was ticking over but, as soon as it was given a bit of throttle and some torque was applied, the pinion had sheared its locating peg into the end of the timing-side main bearing journal. This little breakage had very efficiently disconnected the engine from the rest of the bike. Kicking over the engine only turned the timing pinion while the engine itself remained entirely stationary. I was able to drill out the old remains and insert a new peg. With the new peg in place and the timing pinion bolt done up properly the engine ran just as it should...
Over the next few months I enjoyed many a happy mile on the Terrier. For a 62 yearold, basic four-stroke engine of only 149cc it really is a surprising little machine. It’s let down only by the awful, harsh suspension which means that any pothole or bump will jar your fillings out.
At about that time, early 2018, I made a momentous decision. Age and health concerns prompted me to sell my Terrier, my equipment, tools, hydraulic ramp, lathe, etc and concentrate on providing information about Tiger Cubs and Terriers for the VMCC and the Cub Club. I continue to run the Tiger Cub and Terrier Register, a source of information all things Tiger Cub. The register lists over 12,000 bikes, frames and engines still ‘alive’ worldwide. Not too bad a survival rate for a bike that was originally intended purely as a commuter / learner model and a stepping stone towards the larger Triumph twins!