Triumph unit twin rebuild.
One step forwards, two back, is the nature of buildingamotorcycle from a pile of bits.
Anyone who has ever thought about assembling a pile of loosely relatedmotorcycle bits into an actual motorcycle, will appreciate certain things are needed for such an enterprise. After more than 40 years ofmucking around with motorcycles, I should perhaps knowbetter.
Even if unlimited funds were available
I’d probably not ship the whole lot off for someone else to do – after all where’s the fun in that?
Nor do I have unlimited time as a living has to be earned. Then of course there’s the unlimited bits thing.
Howmany readers remember the breakers’ adverts in the weekly press in the 1970s, with lists of parts fromall conceivable British motorcycles? Usually in the back of the classifieds, these block adverts listed, at what now seems to be ridiculously cheap prices, ‘frames selection – Triumph, BSA, Norton, from £3’ and so on. I seemto recall Trev’s Motorcycles being one of the major ones involved in this early formof recycling – you still out there, Trev?
Oh to have a time machine to return to that erawhere the bits were available, then I could pick up a new distributor rather than pull the old one apart. Last time the distributor was up on the bench and stripped for inspection – I’m lucky enough to have space to lay such things out and know theywon’t be disturbed– I realised there was one major bit missing and another bit damaged which was the reason why a) the unit wouldn’t turn and b) if it had, wouldn’t produce a spark. Missingwas the carbon fibre brush in the cap, this presses on the
rotor and without it the spark can’t go to where it’s needed.
Distributor Doctor had a genuine Lucas bit for the same price Triumph forks were listed in the 1970s adverts and it came quickly in the post. The damaged bit was the cam which sits on the shaft and action plate – as described in the parts manual. It did take a bit of removing thanks to the crud built up over the years, but some gentle warmth and easing fluid did the job.
The damagewas to the top of the cam where the rotor sits; the end is bored, a locating screw goes inside to hold it in place on the shaft and the rotor sits on it, or would if it hadn’t been squashed and bent. There is a slot in the camwhichhad closed up and needed easing apart and reforming by gently clamping it around a round bar of the correct size. This took quiteawhile, as I worked very slowly until the rotor sat properly, though there is a certain fatalism with parts in this sort of condition. By thatImean it didn’t work because of the damage and I could only make it slightly better. To be honest the thing should have been replaced but all I want for the moment is to get to the stage where a spark can happen with things cobbledup so they at least work.
Once the rotor could do its job, assembly was straightforward as clean parts are a delight toworkwith. Once again the paradox of this engine came into play; it seems to have lived a hard life but wear on some components is minimal. Despite the damage to the distributor camand years of grime, the actual bush in which the shaft spins was a good fit, allowing the shaft to spin freely with no side-to-side play. Any sloppiness in this area will translate to quite an effect on the timing as the shaft wobbles about.
Therewas an issuewith one of the bob
weight spindles being loose. These bobweights are locatedunder the points plate and are flung outwards as the shaft spins. I’mnot sure if the loose spindle would have made much difference to the unit, but it is a simple thing to delicately peen the rivet a little and tighten it up. Thanks to taking photos as I stripped the unit and having an exploded diagram handy, assembly went quite easily.
With all the spinning and revolving things in a distributor, lubrication is quite important, but hoofing loads of oil on is probably a bad thing. For this little unit, I dipped a small paint brush into a pot of light oil and coated the spindles, shafts and whatnot with enough to do the job, but not attract too much dirt.
With reference material onhand, the unit went back together very well and the final task on the body was to pin the drive cog on the bottom of the shaft, which engages in a cog on the inlet cam. I left this until last in case I had to pull the thing apart again. I could now see to the distributor cap.
Using a gentle cleaner, years of grease and crud were removed and the cap seemed okay. Where the ignition and coil leads pushed in needed cleaning inside as there were traces of oxidisation. A fine wire brush in my Dremel soon cleaned the insides up, then a bit of contact cleaner got rid of any grease, the brass cable clips cleanedupwith awire brush and more cleaner and once fitted back on the distributor it could go in the hole in the cases.
Another bracket
I’ve been putting offadding a bracket to the rear of the sub frame where the mudguard comes close to. On a 3TA – and 5TA and T100A as well – of this vintage therewould be a flat sheet mudguard hidden by the ‘weather protection panels’ as Triumph called them officially, but known as ‘bathtubs’ by the world in general, so a standard typemudguardwas not intended to fit on suchamodel. Variationswhich do have a standard mudguard include the
inspiration for this project and Triumph had their ownway to hold rear guards in place.
The standard steel guardwould have a steel strip riveted to it which then fitted onto the rear damper mounts plusaU-shaped clip going over the frame tube at the rear. This seemedunnecessarily complicated to me and with no need to adhere to originality I had a bracket welded to the frame, linedup the guard and drilled a hole through both. The guard is now located at the front, middle and, with the grab rail in place, at the rear too. Of course, in order to have it welded the sub-frame had to come off…
Sitting comfortably
Putting the sub-frame back on to the bike, I thought a bit more about a seat which, thanks to frame modifications done a few years ago, will require special fabrication. Were it a trials bike then a simple alloy plate with a bit of foam rubber glued to it would suffice and just such a seat has been on my BSAB40 for a lot of years. But this is to beamuch morewidely used bike and a more comfortable seat is envisaged. Some plywood handily lying at the back of the workshop was shaped into something seatlike and dropped onto the frame to formthe basis ofamould.
Once the former is to my liking, modified by looking at it fromadistance and chopping it off to length until it looks right, I’ll either acquire a glass fibre kit and make a base, or have an alloy one beaten to the right shape.
As you can see from the pics, the seat base has to fit over the top of the mudguard. Triumph and likely other manufacturers used a pressing with several shapes to do this, but I just carved away at the available plywood until it slipped over the guard. In retrospectmaybe I shouldhave left the frame off and done the job on the workbench, which would have been easier.
While I’monwith this bit I’d like the seat to be easy to remove or at least lift up to allow access to the oil filler cap, which I feel will be under the seat. The ISDTbikes had special seats which hinged at the front and used the quick release pin of the standard seat as catch. Currently on the plywood former is a block screwed in place with a bolt through it which locates into a frame bracket, which happened to have a convenient hole. This holds the front down and once a proper base is constructed, then a bracket canbe riveted in place or bolted if that’s more convenient and fittingmade so it will just push into the hole in the bracket. A couple of bolts at the backwill hold it all in place andImay use the Triumph method of brackets fitting over the rear damper bolts to do this orImay not.
Now, let’s see if the battery has charged so I can try for a spark…