Black Dog Classic Motorcycles
After completing the first 500 miles after restoring my Brough 1936 Matchless SS 80 a few problems had arisen, the main one being the gearbox and clutch. The Norton gearbox had a whine in 2nd & 3rd and sometimes it was stiff to change gear, this was annoying and spoilt my rides because I hadn’t checked all the components when first assembled. The Norton clutch, which came with the Brough, was in reasonable fettle and the only things renewed were clutch springs and the shock absorber rubbers. The plates were free from distortion, the inserts proud and even, though a few were loose in the clutch drum. Even in this condition the clutch gave trouble, once warm, it took up the free play from the clutch lever, and the clutch dragged, making it awkward to select neutral when stationary and becoming a pain in traffic. When the clutch got over warm, it would start to slip, I soon lost patience, as this was spoiling my rides on the bike.
The Brough was laid up for the winter at the end of October. I held back from stripping the box, until I had some information on gearbox ratios and also the lengths of the external gear linkage arms, on the side of the box, these arms are modified Norton ones, being shorter than the standard Norton arms, in order to clear the rear cylinder exhaust pipe and the frame down tube. At first I though I might have a mixture of Norton Inter and 16H gear pairs. This could have been done in the past for sidecar use. The Brough owners club supplied the information on arm lengths and gear ratios, part numbers, number of teeth etc.
The gearbox was removed from the bike, stripped and washed in white spirit, this done on the garage floor and mopped up with newspaper and rags. The gear cluster was blown dry with an airline and put to one side, the newspaper and rags were used to light the garden rubbish, two days later, after searching the garage for the lay shaft roller bearing, I found it in the ashes of the garden fire! First lesson, when stripping anything down, make sure that you have all the pieces, before you throw away the cleaning materials. The gearbox ratios were found to be all Inter as standard and the whining was put down to the two floating gearwheel bushes, these I suspect, have been made out of brass. Two new genuine ex WD gearwheel bushes were purchased from Russell Motors, together with a new lay shaft bearing. The external selector arms when measured, were slightly different lengths than the dimensions I had received, so the gearbox was assembled without the shafts and cluster, I then removed the cam plate spring plunger and fitted the gear lever. If you look down the cam plate spring plunger hole, onto the cam plate, every time you move the gear lever, one of the notches in the cam plate, should line up with the hole you are looking down. I tried changing up through the selector range then down the range and every time a notch aligned directly under the hole. So I did not alter the arms, as they were only a few millimeters off the dimensions given.
I reassembled the gearbox, with two new oil baffle shims, fitted to each end of the main shaft, checked in the vice for selection and fitted back into the Brought. The clutch was treated to a new set of friction clutch plates, and the inserts in the clutch drum removed and after having a thin, solid disc of friction material, bonded to either side of the clutch drum, by a local brake and clutch specialist. I had read somewhere that with these new plates fitted, you can run with one less plate fitted, this I did and the clutch now works perfectly, this with no expansion of the plates which took the play out of the lever as before. I have also altered the engine breather, it now passes through a hole in the rear of the primary chain case, and blows onto the front engine sprocket, instead of the rear chain and back tyre. The gearbox has lost its stiffness when changing (due to the new clutch?) it has also lost its whine in second, but still has a slight whine in third, this I put down to the gear profiles, this gear may have had a hard time in the past if a sidecar had been hauled about. A lesson learned with these old Norton clutches, fitting a new set of plates will transform your clutch! The engine has given no trouble, but the carburetor could do with a bit of work, it does not seem very sensitive to the airscrew and is a bit thirsty. I’ve also learned to stop sticking it into 3rd when coming into a bend, it goes round in top and pulls away cleanly, but that’s the character of a V twin, I suppose I’m used to riding singles. We will have to wait to see what happens after the next 500 miles.
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