‘Nothing seemed right... the seat looked too high... to be frank, it looked a mess’
Reader Simon Davies’ query about saving money when building a special, by undertaking small engineering jobs yourself (next page) was underlined by my mate Mick, who’s restyling his café racer Norton Atlas. Lining up a tasty alloy seat unit, he realised it would need to be raised off the supplied brackets to clear the rear mudguard. He drew up what he thought he needed and took the frame to a fabricator. After parting with £250 he found himself unsure how to attach the loop for the mudguard, so I told him to bring it round. Nothing seemed right; the mudguard loop didn’t line up and the seat looked too high, revealing the bracketry beneath. To be frank, it looked a mess. The first rule when fitting mudguards to specials is to check, not guess, suspension movement. Take off the units and pop off a spring. Then refit the bare damper and lift the wheel to the full extent of travel. Add a bit for luck and, knowing the wheel can rise no higher, you have the position for your mudguard. “Wish I’d thought of that!” Mick grinned.
Indeed, because the problem was now clear; overestimating the wheel travel had led to everything being too high. With the mudguard lower, the seat could be dropped. But even then, the mudguard looked awful, sticking out beneath the alloy seat hump like a gecko’s tongue. It looked better without... So why not just cut down the guard so it just reaches the seat base? Now the seat could go lower still and it suddenly looked ‘right’. All we had to do was weld on a small tab for the top of the mudguard and make a couple of seat spacers, but of course most of Mick’s £250 job was now ground off and in the bin. Worth trying yourself? I’d say it’s essential. There are no manuals for specials, it takes trial and error – and it’s a lot cheaper if the error’s in your own time.
The Big Fix
brave the lathe
How much money can a hobby lathe save you when building a bike?
Simon Davies is gathering parts for a Dunstall Suzuki GS1000 project. He has the engine and frame and an assortment of wheels, brakes and suspension parts from other bikes to complete it. Concerned that having all the necessary brackets, spacers and fittings made up could turn the project into a money pit, he asks: “Realistically, can a hobby lathe enable the home-builder to safely build a bike without throwing thousands at it?” It’s a slightly tricky question; in my case I would say definitely, but it depends, to a great extent, on the individual. Probably the first thing any lathe owner is likely to make is a spacer. Spacers are often needed on specials; every one you make yourself saves you money and, importantly, down-time while you wait for it to be made. It also means if the dimensions are slightly wrong, you can alter it or make another, instead of having to head back to the engineer or, worse, accepting it and packing it out with washers. The aspect of safety is the primary concern.
There’s not much likely to go wrong with a spacer but something like a wheel spindle is more serious; here, the questions are accuracy and material. Accuracy isn’t too bad – it’s right or it isn’t and careful measurement will tell. Material calls for careful research, but there’s a big common sense answer here: if the thing you are making breaks, what could happen? If the answer is disaster, then tread warily. Research is worthwhile, whether you do the job or farm it out. Just because you pay someone to do it doesn’t prove that he knows what he’s doing; research will enable you to ask the right questions. The key thing about a lathe though, is that it grows with you. As your confidence and ability increases, you find more that it can do. The limitation will always be capacity – the size of work piece the lathe can hold – so while small hobby lathes are handy, you are better off getting the largest you can accommodate, or you will outgrow it.
Sticky situations, cam confusion and hard maths
The cork plate is fine but the
steel one may not be
On the subject of clutch problems, Terry Hoare emailed to say he had been gradually tightening springs to overcome slip, until the clutch had become uncomfortably heavy. Stripping it down, he found that although the original style cork plates were still in good condition, the steel ones between had corrosion pits he thinks were creating oil pockets. With new steel plates and thorough lubrication, he’s been able to back the springs off for a lighter, but slip-free lever action.
A quarter of an inch less radius
makes for a lighter clutch
On which subject, it’s not the first time I‘ve said it, but you used to be able to get lever blades with a smaller pivot radius – that’s the distance between pivot bolt and cable nipple. Shortening this radius has the same effect as lengthening the hand lever, so it can give surprisingly lighter operation. The lift will be slightly reduced, but with a clutch in good condition, the lift shouldn’t be so marginal as to cause a problem. The centre to centre measurement is 7/8in on the lighter lever and 1 1/8in on the standard one.
Spring is here.
Clive Chapman asks if I know a source of mechanical advance/ retard unit springs to refurbish the Magneti Marelli unit on his 1956 Moto Guzzi Lodola, or whether he should just replace the whole thing. I’ve not found sources of parts for lightweight Guzzis in the UK. Springs are readily available for Lucas applications, so perhaps there would be something among those that would do. Obviously, the essential priority is that the spring is the right tension to allow the weights to overcome it at the correct revs for full advance. A proper advance curve would be nice, but is unlikely on a mechanical system. Pulling back to full retard is less important. But I thought it was worth asking Mel Robinson at Guzzitech in Glasgow and he suggested the German company Escher (escher.de) who sell spares for the smaller models. If all else fails, I also note that there is an electronic ignition system available from another German company Elektronik Sachse (elektronik-sachse.de).
Shock of the new
I saw CBOTY entrant Lewis Cocksedge at the MCN London Show and he asked if I knew where he could obtain a crankshaft shock absorber spring for the 1928 ‘black’ Ariel he’s rebuilding with his father. I had a word with my mate Pete Kemp, single-cylinder spares officer for the Ariel Owners Club, and he agreed shock absorber parts are a problem for these early bikes. “It’s a different assembly to the later models,” he explained, “But the club has had the necessary adapter made to fit the newer model sprocket and parts to the older engine.” Pete can be contacted at firstname.lastname@example.org and although the club will supply non-members, the benefits of this, one of the most proactive of owners clubs, makes joining worthwhile. Speaking of proactive, Pete drew my attention to the Ariel Klub Slovensko (arielklub.sk). Even before Czechoslovakia divided, there was a massive scene for classic bikes, which displayed incredible ingenuity and engineering skill in manufacturing parts to rebuild machines that had been imported decades before. This industry continues today, with the added benefit that the output is now available to us all over here. The Ariel Klub website is well worth a look for owners of vintage Ariels, you can translate into English and under ‘Message’ you will find several hundred quality reproduction parts for sale at very reasonable prices.
Swap a Lucas ignition lock barrel
Don’t get rid of your nice old key when a Lucas ignition switch packs up – you can swap the lock barrel into a new switch
Karsten Moller-Hansen emailed from Copenhagen to ask in which magazine I mentioned about centring brake shoes to improve performance. That was in the December Fixes and applied to those Triumphs fitted with a ‘floating’ brake shoe pivot. Later models with the floating shoes – ie flat on both cam and pivot end – self-centre automatically. But it occurred to me, while on the subject, that I hadn’t mentioned that Norton front brakes can also be centred. Here, the wheel spindle is a loose fit in the brake plate and the idea is to loosen the spindle nut, push the bike forward with the brake applied and tighten the nut so that the plate is allowed to find its own position in relation to the drum. Useful adjustment as this may be, I have a suspicion that in the real world it caused more trouble than it solved, with owners unaware of this adjustment, refitting the wheel only to find the front brake has puzzlingly lost its bite. You have been warned...
I always wince when anybody tells me their Triumph cylinder base gasket is leaking. The gasket sits on a generous surface, compressed by strong bolts. It’s not the gasket, it’s the pushrod tube seals; trust me. Paul Farrel wanted to know if he might get away with loosening the cylinder base nuts, jacking up the cylinder and squirting in a bit of gasket sealer. Paul’s bike is a 1966 650 bottom end with a ’74 T140 head and barrel. The seal problem is unlikely to be due to the mismatch, so long as the head barrel and tubes all came off the same model. Triumph used several types of tube over the years and it’s important to have the right one (see October 2015). On unit construction 650 twins made before 1966, they fitted a positive oiling system to the tappets, fed through a drilling that came up through the front right-hand side of the cylinder base joint to meet a drilled hole in the cylinder. When the system was dropped, the crankcase hole was blocked off, but there’s a faint chance that Paul’s ’66 is not blocked off and, unable to get through the barrel, it’s leaking out. But I doubt it, and, if it is, the barrel needs to come off to block it. Better get on with stripping it Paul, before the sun comes out!
it’s all in the timing
Surely something must be to blame for my cam problem. Even if that something turns out to be, well, me...
Looks like I spoke too soon about having solved my Gold Star valve timing woes (Our Classics, March). Checking the new exhaust cam more accurately, with a dial gauge, reveals that it still closes the valve 10° early, the previous cam being 15° out. What’s weird is that nobody I speak to seems to have much to say about this. To me, that suggests three possibilities:
1) They don’t trust my readings, I understand that. I’m pretty sure I’m right, but we all make mistakes.
2) Since few road Goldies are likely to get revved out and racers probably use different cams, maybe nobody else has detected the problem.
3) It doesn’t matter and the problem lies elsewhere.
I rang ABSAF in the Netherlands and, having discussed Problem 1 and suggested Problem 2, ran straight into Problem 3. I explained that years ago the piston had just clipped the head, so I fitted a 20 thou shim beneath the cylinder. After all, it barely affects the compression ratio, so why not? The answer came back, sharp and clear: “Well that will ruin the squish effect!” snapped proprietor Jan de Jong. Er, what? Really? A follow-up chat with my mate Bruce Hazelgrove confirmed that this is worth checking and, admittedly, the shim was fitted at the same time as the first set of ‘suspect’ cams. Maybe the butler did it after all…