If you are contemplating restoring a machine it’s best to make it as authentic as is reasonable. It will look and ride like it did when the new owner brought it home and proudly showed it to his family and his mates. You won’t run into problems when licensing it and it may be more valuable. The Club defines an authentic machine as follows. The machine must consist of at least four or the original six major components that is engine, gearbox or transmission, frame, forks, petrol tank and wheels. To be classified as original the components must come from a machine of the same make and type, but not necessarily the same year provided that the model concerned was manufactured basically unchanged over a period of years. Faithful reproduction of two of the missing components is acceptable. Over the years tin ware like mudguards and tanks rust, controls and lighting components are removed, bikes get modified and bits get lost. You have to make them, get them made, swap or buy them. Reprinted parts books, pictures and the Club library are good sources for finding out what the parts you have to make or otherwise acquire look like. The handle bars that came with my bike were only fit for scrap. The original bars were 7/8th inch diameter with a bulge to 1inch at the centre where they fit onto the bike. I found a place that sells imperial size tubing. (They make roll cages for competition cars.) I turned up a 1inch sleeve and welded it to the centre of a straight bar. I made it known that I needed someone to bend the bars for me as I reckoned if I did it they wouldn’t be recognisable as handle bars. A talented Club member and a slab of beer got me a “sporting and a touring handle bar.” I chose to fit the touring bar. This Triumph came with either a lever throttle or a straight pulling twist grip control. When the twist grip option was chosen the bike came with a twin lever control to operate the choke and the ignition advance and retard. I had a twin lever control but one of the levers was broken off. It had Triumph stamped on it so it had to be resurrected. I found a 50’s choke control in the Club store and with some modification it fitted into the control body. I turned up a handle that was close in appearance to the existing one and welded it in place. After the component was nickel plated it looked the part. The bike was fitted with a rear stand which lifts the machine high enough to allow the rear wheel to be removed or can be used to support the bike when it’s parked. When not in use it swings up and is secured in a clip on the mudguard. There is a u shaped plate which attaches to each leg of the stand and butts against the frame when the bike is on the stand. A friend of mine had several extra u shaped plates laser cut when he did his restoration on the same bike so I was able to get hold of two and make a stand. The front mudguard stay doubles as a stand for removing the front wheel. I located a stay and purchased it. On inspection it looked sound but it turned out to be paper thin in places. The small drain hole at the bottom was blocked and trapped moisture had caused internal rust. The rusted stand served as a template. (Useless rusted bits can be worth keeping. The Club keeps some rusted parts in the Parts Store. They are very handy if you need to reproduce something for your restoration). I find the best way to reproduce an item like a mudguard stay/stand is to get a solid flat board, place the sample on it and mark the board at various positions around the object. Fit metal pins into the board where it was marked. New tube can then be bent around the pins to reproduce the correct shape. When making sharp bends with tube you may need to fill the tube with sand and seal the open ends before heating and bending. If bending rod, heat the rod to red heat before bending. The feet were removed from the old stand and welded to the new one. I was told that as you pull the bike up onto the rear stand the front wheel may swing to full lock making things difficult and a prop stand would be good although the N type was not fitted with one. I allowed myself this departure from standard in the interest of making life easy. I found an old prop stand in the Club store, made a bracket to attach it to the frame and modified the leg. It works remarkable well. The unusual shape was necessary to allow the rider to get a boot onto it as it retracts under the primary chain case cover. The original twist grip has an outside diameter of 1 and 3/8th inch and the handle bar diameter is 7/8th inch. To keep the feel the same when both hands are on the handle bars, it was necessary to fit a 1 and 3/8th inch diameter sleeve on the left side. A shrink on leather grip will eventually be fitted to both sides of the handle bars. I found that the clutch lever contacted the sleeve before the clutch was fully disengaged. This caused some concern as initially the only fix seemed to be to increase the length of the clutch control lever which wasn’t possible as the end of the lever lined up with a hole in the frame through which the clutch cable passes. Another suggestion was to relocate the lever pivot point. I eventually solved the problem by grinding a bit off the forward end of the lever so that in the rest position the lever dropped down further before it contacted the bracket on which it pivots. This allowed the cable to pull further before the lever contacted the sleeve on the handle bar. A simple fix. All the other cables were made, nipples turned and soldered in place. Not a job I like!
Other items that had to be obtained were a tool box, which was kindly made by a member, a gas lighting set obtained through Club members, brackets to hold the gas generator and headlight, a basket for the carrier (I bought at a market), a license plate holder for the back mudguard and other small items. I had no idea how to make the license plate holder. A friend told me how. Cut out the shape you want in cardboard. Trace around it on a strong (jarrah?) piece of wood say 3/8th inch thick. Cut the wood to shape. Get a piece of suitable thickness plate and bolt it to the wood. Cut the plate around the shape of the wood (I borrowed my neighbour’s nibbler) leaving enough metal to bend over. To ensure rigidity, with a suitable hammer tap the plate over the edge of the wood. Cut vees where necessary at the corners. The vees can be welded up later.
So most of the work is done. It is now time to set the timing, put some oil and fuel in it, see if the thing starts, see how much oil leaks out and from where and how to stop it.
Pics by Broddy1940
After months of trying to source an original clutch it became obvious that there just wasn’t one available. A friend of mine in the Club said no worries we will make one. (I’m not naming people because I might forget someone who helped me). I had one component of the clutch and that was the splined ‘clutch driving member’ that fits the driven shaft of the gearbox. The clutch driving member also has a large diameter track to take the bearing on which the basket runs. I was fortunate to have this component as manufacturing it would entail machining splines and case hardening the bearing track. The basket that holds the clutch friction discs and clutch plates was spun. A flat steel disc of suitable thickness is retained in a lathe and as it turns the operator applies a tool with a long handle and bends the metal as it turns until the metal is shaped as in the picture. Slots are then cut to take the friction plate lugs. The first attempt using the spun basket didn’t work too well. I welded a band around the basket to stop it opening up as pressure was applied during the operation of the clutch but the addition of this band caused some distortion and balance problems. The fix was to machine a basket out of a piece of large diameter aluminium bar. Another friend machined the basket and milled the slots to take the clutch plates. New AJS parts are used for the plates, the clutch springs are modern Triumph and rollers are used in the bearing.
The clutch is driven from the engine via a chain wheel attached to the basket. The number of teeth that can be accommodated on the clutch chain wheel depends, to some degree, on the overall diameter of the clutch which itself is governed by the diameter of the clutch plates. The clutch and chain wheel and chain have to fit into the primary chain cover which is designed to accommodate fore and aft movement of the gearbox to allow tensioning of the primary chain. The unit had to be made to fit or else the primary chain case cover would need to be modified. My main consideration, however, was to keep the final ratio the same as the original bike. The ratio is all about how many times the engine crank shaft turns over for one revolution of the back wheel. If the ratio is considerably different from the factory spec. the engine will either be revving fast or labouring in a particular gear for a given road speed. Apart from the design of the gearbox, the ratio depends on the number of teeth on the engine, clutch, gearbox and rear wheel sprockets. In my case the gearbox and rear wheel sprocket were factory original and the clutch sprocket was fixed by the dimensions of the homemade clutch so the only sprocket I could change to achieve the original ratio was the engine sprocket. The final ratio is calculated by dividing the product of the number of clutch sprocket teeth and rear wheel sprocket teeth by the product the number of engine sprocket teeth and the number of gearbox sprocket teeth.
The original ratio for the bike in top gear was 5.06:1. That is the crankshaft turns 5.06 times for one turn of the rear wheel in top gear. I had the clutch with 36 teeth and the rear sprocket with 38 teeth. Multiplying these together we get 1368. The gearbox sprocket had 15 teeth so I chose 18 teeth for the engine sprocket. Multiplied together, 15 and 18 equals 270. Divide 1368 by 270 and we get 5.06 which is the ratio required. I bought a blank sprocket with 18 teeth, machined the original engine 15 tooth sprocket off the boss and welded the 18 tooth blank in place. When everything was assembled it all fitted OK in the primary chain case cover. The slotted holes in the frame that take the gearbox retaining bolts were long enough to allow proper adjustment of the primary chain which meant that the rear wheel chain adjustment available was still OK. It all looks good but the question yet to be answered is does it work?
After the clutch was finished my attention turned to the handle bar fittings and cables. I emailed UK seeking a period clutch and brake handle. I should have said that I want a period clutch handle and brake handle because the recipient read it as I wanted a clutch and a period brake handle. He could supply both. After making one I was now offered the genuine article. I had to buy it of course and it came in excellent condition with new friction plates. To fit it to the bike I would have to change the engine sprocket again so I’ll see how the home made one goes. Handle bars, fittings and control cables can be a bit fiddly but that’s story for another day.