‘when I took off the alternator I was very pleased that I had given in to my suspicion’
What do you think this is?” asked Perry Barwick, holding up the fragment of curved black plastic he’d just found lurking inside his 1966 Triumph’s primary chain case. Plastic and rubber get hot in there – most likely it was a bit of embrittled alternator lead insulation, but the shape suggested part of an oil seal lip. But time was limited, the cover was off to adjust the clutch springs and Perry had experienced no other problems, so the idea of stripping it down to find it was just old debris didn’t appeal. After all, if it was the crank seal, it’s not a disaster – on later models Triumph abandoned the seal altogether, admittedly with some breather mods... we agreed to leave it for now. But that evening I couldn’t really settle. Back into the shed I went – when I took off the alternator I was very pleased that I had given in to my suspicion. Poking through the extractor hole in the sprocket was a large sliver of steel which, further investigation revealed, had come from the gradually disintegrating carcass of the seal. It had been fitted the wrong way round – facing outwards – so not only did it allow crankcase pressure to release into the case, but also the steel shell of the seal was hard against the rotating main bearing. No wonder the rubber had got hard enough to break up. Fortunately I had a new seal in stock in my Triumph box and after a couple of hour’s work it was fitted – the right way round. But it would have been all too easy to just leave it and hope for the best. This is where I disagree with the ‘if it ain’t broke, don’t fix it’ philosophy. It should mean ‘don’t fiddle with things needlessly’, but too often gets used as an excuse to assume things are OK when big trouble is brewing. The shrapnel from that oil seal would have ended up in the main bearing, alternator or chain – and the result would have been messy.
The Big Fix
Can a bit of jet-setting solve a reader’s Amal quandary?
Henry Raison was disappointed to find his BSA C15 SS80 wouldn’t do more than 65mph. A strip revealed a badly worn bore and a standardmodel, small-valve head and carburettor. After reboring 2mm oversize to accept a Triumph Daytona piston and fitting a big-valve SS head, he fitted a new Amal Concentric as fitted to the later B25 Starfire; slightly larger, he felt it would complement the increase in compression ratio and capacity. Performance is better, but now the bike will only tick over on the old carb. “Should I try another pilot jet?” he asks. “At £15 each I’d like a second opinion!” Well, boring to 69mm will only have increased the capacity by 10cc and any alteration to compression ratio alone won’t really affect carburation. Carb size has more to do with breathing – cam timing and port dimensions. The C15SS and B25 have the same cam profile, but the later engine has larger ports and valves, I think. At 28mm, Henry’s new 928 Concentric is 2.5mm larger than the original 1in (25.4mm) Monobloc which will reduce gas speed, tending to richen mixture. I suspect a 626 carb would have been a better choice – the bore is correct and it’s a smaller carb altogether, more likely to be in proportion in other respects. The standard air screw setting would be around 1½ turns out from fully home; screwing it out weakens the mixture, so adjustment should give some idea which way to go with the jet. Concentrics usually need about a 30% smaller main jet than Monoblocs, so it might also be worth dropping to a 150 – but this won’t affect tickover. Fitting anything that is not a direct replacement always requires a bit of experiment (and cost). Hopefully Henry will get it right first time!
Rick checks his threads and gets gasket input
Colin Porter emailed to say that a 5mm x 0.5 tap is 51.8 tpi, whereas 2BA is 31.35 tpi, so my suggesting of tapping out a weak 2BA thread to the metric size doesn’t work out. Colin was obviously right, but if so I couldn’t see how the threads on a 5mm and 2BA bolt look so close back to back. My fault – the tap you need is 5mm x 0.8 pitch, which works out at a much better 31.75 tpi. I’d selected a nice shiny tap for the photo, not realising it was a different pitch. Sorry, I guess that’s showbiz for you! Come on, they do look similar...
Chris Stevens of classictrial. co.uk says the piston contact issue I had with the project Yamaha RD200 may have been due to pattern parts. Pattern gaskets aren’t always big enough to accommodate rebores, and piston crown height is sometimes wrong, as he’s found with Honda TLR 250s. I don’t think that was the problem this time, but thanks for the tip Chris. Pattern gaskets: not always best
Ian Senior contacted me to ask if there is anyone who reconditions AP Lockheed brake calipers of the type fitted to late Triumph, Bonnevilles, Tigers and Tridents. I don’t know of a brake specialist that carries out this work, but I had a word with Triumph specialist Arthur Frearson at Rockerbox (01252 722973), featured in the September issue of Classic Bike. Arthur says he can do the job, which usually involves stripping, cleaning and replating (if required) the caliper shell before rebuilding it with a new seal kit and stainless steel pistons. Although Arthur leaves pricing to business partner Darrell, he guesses it would be somewhere in the £100 bracket. One thing to remember when rebuilding your own Lockheed caliper is that there is a seal between the two halves of the shell. Years ago, this seal was not included in the Lockheed seal kit, which meant that it was unwise to separate the two halves. It was a daft omission that made proper cleaning difficult, but Arthur confirmed that nowadays the seal is included, so that’s good news.
Give me a steer
Steve from Liverpool emailed my website (rickparkington.co. uk) with an unusual problem. Fitting new head bearings to his T160 Trident, he found that the steering stem was cracked vertically. “I can only put it down to a combination of old metal and bad luck!” he says, asking if I can suggest someone who could repair it. It is certainly an odd one. The load the fork stem is under is largely tension, the actual fore and aft loading of braking etcetera being supported by the headstock, yokes and bearings. The primary job of the stem is to hold the yokes together to enable them to perform this role and if you look at Greeves’ light and immensely strong leading link fork you will find the stem is just a 7/16in (11mm) stud running between the yokes. It’s a relatively straightforward job to have a new stem made, although since the threads will not be metric, choice of material is important and it needs to be fitted correctly and in line, the old stem would need to be bored out and the new one located with pegs and brazed in place. Some sort of jig would be required – the top yoke and fork tubes (preferably an old set, they may get hot) would probably serve. I’d recommend somewhere like Jake Robbins’ Elk Engineering in Hastings, East Sussex (07986 254144). I rang Jake, who says that although he would need to see the job to quote a price, he could certainly do it. But first I would try to get a replacement yoke. I actually picked up a T160 yoke by mistake when I was looking for a T140 one for the Classic Bike flat tracker project a few years back – I no longer have it, but I guess other examples must still be out there and it would prove a quicker (and probably cheaper) solution.
Adjust Triumph steering head bearings
Triumph’s headlight nacelle is attractive – until you have to adjust the steering head bearings. But here is an easy way…
Nick Goodwin has a rigid BSA B33, and although he claims to ‘ride it conservatively’, he would nonetheless like to go a bit faster sometimes. He says: “I met the owner of a B31 who had shoved Goldie cams in his bike and he said it flew… however, people do the waggy finger thing and say that it causes too much stress and ruins them… any thoughts on this and whether it’s worse on the B33 (500) than on the 350cc B31?” Well, the Gold Star has a stronger bottom end, with larger main bearings, but even so the crank is a weak spot because the main shafts have a flange which is rivetted to the flywheel once the shafts are press-fitted home. It’s a design that worked fine in the vintage days, but began to suffer as power increased. Frequently the shafts work loose in the flywheel until only the rivets hold it all together. The B-series models, having a weaker crank, are possibly more susceptible. But the DBD Goldies have big valves and ports to go with the wild cams, so while fitting a Goldie top end onto a B33 bottom might be risky, fitting perkier cams to a B single isn’t going to cause the same problems. DBD Clubman cams are too furious, designed to match the huge ports and carb, and probably wouldn’t work that well. But the Touring Goldie cams (65-2448 and 65-2450) are supposed to work well in a B31/33, taking the timing from 25/65 – 65/25 to 43/73 – 70/45 – in other words keeping both valves open for an extra 25° of crank movement. Although BSA singles were well made, they were also largely tuned with a bias towards fuel economy back in the 1950s, so there is usually space for a bit of tuning without affecting reliability.
willing and cable
Jeoff Peck emailed to ask what kind of solder and flux to use when soldering cables. Well, look out for a cable-making feature coming up soon, Jeoff! But in the meantime I would say that all I ever use is conventional electrical solder and Fluxite flux (or Bakers Fluid if the cable is at all corroded). Solders come in various types, and particularly grades of toughness – but the harder they come, the greater heat they generally require to fuse; this is where you run into problems with overheating the cable, which can leave it more liable to breakage. Generally, as long as you make a proper job of the soldering and have managed to form the end of the inner inside the nipple, a soft solder is sufficient. For forming the cable end, Venhill make an excellent ‘bird caging’ tool to which I am a recent convert. It isn’t cheap, but it’s a sound purchase if you make your own cables. I’ll tell you all about it in the feature...
i was robbed at the kop
Rick’s runs at the famous Kop Hill Climb fail to live up to expectations due to the Martinsyde’s wayward behaviour
Bit of déjà vu this month. After fixing the Martinsyde’s head gasket, we went for a very enjoyable weekend at the Kop Hill Climb. It’s a smashing event for competitors and spectators – a charity event with friendly organisers featuring bikes, cars and various entertainments, it’s one of our favourite events of the year. My first run up the hill on Saturday revealed the Martinsyde’s twin carbs need further attention, starting easily but hugely rich above idle. Solution on the line was to whack open to full throttle whereupon it cleared and took off. There’s limited adjustment on these carbs and the air screw seems to have a wider effect than usual, so I tuned the screws in the paddock. This meant revving the unsilenced bike like an annoying kid on an FS1-E. It was much improved in the afternoon – the old warrior fairly leapt off the line, but after blaring up the first 100 yards a different roar announced the front head gasket had blown again and I had to take the ride of shame back down the course to the start line. This time I have fitted the gasket with Green Hermetite, a hardening compound (glue) designed for warped car heads, I believe. It’s all back together now and ready for the next battle. Either there is A Problem or I should have tightened it down a few times before opening up. We’ll see...