TRIUMPH/TWN ‘CORNET’ ENGINE AND GEARBOX STRIP DOWN.
In 1984 i restored a TWN ‘Cornet’ at the time the motor was in good running condition so it was left alone now almost 35 years later having gone full circle i am about to restore another ,But this time the ‘Cornet’ is all in pieces!The problem is there are no workshop manuals available! all i have is a illustrated spares book that covers both the kick start and electric start models and with all the parts i have got there are parts from the TWN’Contessa’ scooter!(The ‘Contessa used the same engine) so the situation is a bit like doing 3 jigsaw puzzles at the same time! But at my age keeping the brain active is a good thing,So pictures below will show how i am getting on.
The crankshaft’s below will need all new bearings the 2 bearings either side of the crank known as M25 & M20 angular contact bearings made by SKF are like hens teeth!! none available in the UK i manage to track down a specialist bearing dealer in Germany who still had some in stock! but they come with a very expensive price tag!!
Two new pistons were needed ,which were found in Germany. Now fixing 2 pistons into barrels on a split single is one of the hardest things to accomplish without braking a ring but pictures below show the safe way to do it. Also one of the gudgeon pins has a blank end! so where does it fit.I got in touch with the Triumph(German) Owners club and they kindly sent me a diagram showing it’s correct position.I dont think it has any effect on engine performance! it just helps with pin removal.