Triumph unit twin rebuild

Sometimes a statement is so succinctly and perfectly put that its meaning sticks in the mind only to resurface a long time later ... and sets off part of a project in a slightly different direction.

Am I the only one who finds wiring diagrams to be so much coloured spaghetti, or the components these wires attach to equally mystical? Perhaps it's because the parts used in these areas of a motorcycle are not frequently bandied about in the way cams, cogs and compression ratios are.

Maybe it is a glamour thing as ''... fitted lumpy cams, skimmed the head to get the compression up and built a close ratio cluster using cogs from three different models to keep the revs in the power band .. :' is more impressive to your mates than ''... swapped the old bullet connectors for modern spade ones, cleaned up the terminals with a wire brush and contact cleaner and got a brighter light .. :'

If ever an area needs to be logically thought through it is the electrics, as so many components need to be compatible otherwise awkward things happen such as wires melting, stators burning out, light bulbs popping etc.

One of the problems is that electricity is invisible until the spark plug produces a spark, but there are various points where its effect can be felt. If you're starting out with a complete motorcycle which was working and was then stripped, the advantage is all the components may be reuseable in the short term. Unfortunately the less easy option was taken here and a bike assembled from bits lying around.

With no reason to stick to a cataloguecorrect build, any number of options open up. The problem is such a method can cause things to hurtle out of control if you're like me and actually unsure what is needed. For instance, the basis of the bike is Triumph's neat 'C' range unit twin, and within the 350/500 brackets there are a range of options as to what the bike could look like, covering nearly 20 years of development. It also covers the early use of AC electrics with an alternator stuck on the end of a crankshaft which sends a charging current to the battery via certain control units and the battery sending the current on to the spark plugs and lights. Initially of 6v, they grew to being 12v as the larger voltage covers up the inherent losses through connectors in wiring better than the smaller voltage. There's no reason a 6v system can't be made to work if all parts are in tip-top condition, but it is often easier to convert to 12v.

There has been an underlying theme to this project which is the resultant machine will be 'off-roady' in appearance and, seeing as it's mine, will be 'off-roady' in action too ... but will be road legal. It helps Triumph produced some attractive looking machines

both as production - the TR5AC - and special ISDT machines for British team use.

In the boxes of bits this bike is being resurrected from, there are all sorts of things such as alternators, rotors, rectifiers and capacitors, all aimed at providing a light at either end and a spark at both plugs.

The bulk of this bike is a distributor motor - as opposed to a points-in-the-timing-case - and I was initially going to try for points in the side because I wanted a battery-free system. So I hung an alternator - 6v though wired for 12v by connecting two of the wires together, a practice which is fairly well known in the old bike scene - then I started to connect all sorts of bits to try and provide power to the Lucas distributor. This was not entirely successful and after confusing myself completely, I was standing

staring at the bike and muttering all sorts of profanities when it occurred maybe I should aim for a most basic ignition-only system. More fiddling with bits I don't understand went on, followed by more standing and fuming. All the while during these attempts to create a spark I was turning the engine over on the kickstart, which dropped oil from the return feed on the bench.

With no oil tank fitted, there was nothing to catch the oil being pumped around, okay there's only the amount which was added at the build stage but still... so, in desperation to achieve something I set to and added oil piped to the union block and used a one litre plastic oil bottle to provide a temporary tank. Does it work? Yes. Will the bike run like this? Of course I don't intend to run the bike like this, it is a stop-gap because adding the air filter and carburettor to the bike highlighted another problem ...

I've been carving a wooden former into shape for a while so I can have an alloy tank made and was just getting the shape right without the carb and filter on. Once they were in place, the wooden buck didn't fit ... the air filter was in the way ... more fuming and Plan B was devised, hence the plastic bottle. One of the reasons a standard tank won't fit is because I had the subframe altered in the 1980s with the thought I might make a trials bike out of the bits. So, instead of the curves of the standard frame, there are straight tubes from the damper mounts to the front frame mount. There will be more woodwork to create a different shape tank once I do some research on tank shapes - or as my other half puts it 'looking at pictures of motorbikes again' - and sizes.

While all this was going on, there was more thought about what to do with the power. Hanging various bits here and there more in a 'let's try this' than with any real plan wasn't working and the thought of 'all I want is a spark' kept cropping up.

Then there was a flash of inspiration ... one of the magazines in Mortons' group which it has been my pleasure to be associated with is Classic Bike Guide - I was editor for a long time - during this period I went to see a lad called Al Osborn for a feature on electrics. Al did and still does trade under the name AO Services and has been providing electricity to older motorcycles for a long time.

Those who know Al will understand he has a certain 'way' about him, but if good advice is needed along with a selection of bits to make your electric life much happier, Al's your man. One of the things he impressed on me during my visit some years ago was 'the battery runs the bike, the alternator just charges the battery' and this popped into my head as I was trying to feed the alternator wires behind the gearbox sprocket. More thought along the lines of

'do I actually need a charging system at this stage, as all I'm going to do is run the bike for a few minutes at a time'. A battery would provide the power to the coil and on to the distributor for long enough to make the bike work, okay I'd have to keep charging up this total loss system but for the moment this would work and, ooh look, there's a brand new Lucas motorcycle battery which came from BOM Batteries a while ago kicking about - flat as a pancake though but, hey,

I've a charger. A few wires to connect things up and earth it were quickly done and all

excited I turned the engine over with the plugs out and earthed against cylinder head ... nothing, not even a tingle when I held my thumb over the contact. .. on the plus side the oil was now going back into the container.

Something else Al impressed on me was the need for cleanliness in the electrical department. All systems lose some power or current at connections but filthy, dirty, corroded ones will stop any power at all from doing its job. Lifting the cap off the distributor explained why there was unlikely to be a spark produced by this unit any time soon. Not only was it choked with grime, but the points were corroded and the small carbon fibre brush in the cap was missing. Now a distributor - Lucas' 18D2 in this case - is a mechanical unit, so I didn't have the same fear of the unknown about it as, after all, it's just nuts and bolts. Admittedly, they are delicate nuts and bolts but, working carefully, the unit was stripped down as far as I could get it without asking advice from someone who knows more about these things than me.

As you're reading The Classic Motorcycle it's likely you'll be aware of Old Bike

Mart and perhaps have seen Martin Jay's Distributor Doctor advert. As well as making distributors work better than they did when new, Martin also knows a thing or two about them and has bits - lots of bits.

The way a distributor works is the body is fixed to the crankcase - either in the old magneto position or in the top of the crankcase depending on the make of bike. In unit Triumphs, the inlet cam has a skew gear on it which mates with a cog on the distributor shaft, which turns the workings of the distributor. This cog is held on with a pin and needs to be removed by punching the pin out so the shaft can be withdrawn and the insides of the body cleaned up. The pin seemed to be parallel, but just in case it was tapered, I held off whacking it with a hammer and punch until I asked the question. Yes, it is parallel, but the ends are belled out so it doesn't move in service, so some careful work is needed to remove it and a new pin to replace it.

It is probable the bush is worn, so even when the bike fires-up the ignition will be questionable but, at this stage, the intent is to get it working then sort out a few • other things afterwards.

Temporary oil tank in place, so no more drips on the bench.

l: Adding this air fllter meant there was less room for the oil tank. 2: Adding the oil lines was quick and simple.

3: Obviously, they're a bit long. 4: Once trimmed off, they do the job until a better tank is made.

5: To be honest, I was less than happy with the shape of this one and had almost decided to change it ... 6: Then the air filter forced my hand anyway. These air fllters are tough guys, y'know! 7: It looks like coloured spaghetti and I was floundering around not really knowing what to do. 8: Who else can see the surprised face here?

9: There was no way the crud and missing parts in this distributor would allow it to spark. 10: Working carefully, a distributor comes apart reasonably easily, though the components are delicate. A lump of wood makes for a decent holding jig, but be aware of sawdust.

II: Light oil and careful cleaning makes an improvement. 12: Under the points plate is the advance mechanism - it too is filthy and sticky with dirt and grease. 13: Most, but not all, of the parts are apart and cleaner. Still to come off is the cog on the shaft. 14: Part number three - brush and spring - is missing, while part number 22 - securing pin - will probably be unusable after removing.