Hi, whilst not being a cub specialist, there are a couple of things that can be done to the frame to improve it. Firstly, the headstock is not noted for its strength, so a brace should be fitted where the tank mounts bolt on. this can be home fabricated if you have the necessary equipment and material. This may mean that a different tank will have to be fitted,it needs changing from the original anyway really. The footrest mountings need changing, to enable the new footrest position to be achieved,ie further back and a bit higher. The rear fork/swing arm is not really wide enough for a 400x18 tyre to fit without fouling fork and probably the chain too, so an alternative needs to be fitted. These can probably be picked up from a cub specialist, although I believe that a C15 one can be made to fit. The original front fork is a bit wafty, so that can be improved upon a great deal, check out the dismantlers, give Terry Weedy a try too. I used modified Triumph Adventurer forks on my B40, they needed a bit of work, but work beautifully if done right, or of course, if you can afford them, Cerianis. Sammy miller does nearly all the bits you will need, but I found it very expensive when I could have done the work myself. For a second mortgage, you could buy one of his ready to go frames with all mods done.
