There's problem with the straps that are now sold. The strap metal is thicker and thus doesn't immediately bed in as well as the originals. One has to keep a check on the straps, as over time they more correctly follow the line of the magdyno and thus slacken; quite apart from any locknut, or not.
As to Ian's last resort of having to get another set of cases: well it's undoubtedly the correct option from an engineering view point; but I chose what Ron has suggested and it's lasted for 8 trouble free years without noticeable degradation. My M21 is worth perhaps £2000 in today's market. Fixing all it's faults would cost far more than it's value and add not one jot to my enjoyment of it.
Everyone to their own but I wouldn't be inclined to promote some of the procedures described as good solutions...
I ran a business restoring heavyweight BSA single engines for nearly 20 years after I left my engineering career and have owned various examples for over 50 years...I try to post what I feel is the best procedure based on my experience but what people do with that information is entirely up to them...
Personally, as an engineer, I feel many of these 'fixes' should be avoided if at all possible and should only be employed as a temporary fix until the job can be carried out to a decent standard, not as a prefered way of working...Are we really going to make a virtue of deliberately avoiding doing things properly?....I'm guessing you don't make clogs with such a gung ho attitude....Ian
You win the prize for the most magdyno platform wear for 2025! What you have is very bad. As Ian stated the magdyno and platform should both be perfectly flat. This is a very common problem and I expect to see it anytime I work on a B or M series. Check the mounting strap anytime you ride the bike. They do come loose.
I fix the problem by milling the platform flat and add a aluminum plate to bring the height back up. If really bad, I sometimes have to weld it.
When the magdyno is this bad, I usually look for a better magdyno body instead of fixing the old one.
You are going to have to visit a machine shop and possibly a welder to fix this problem.
If you have not taken the magdyno apart, I would do it. When the magdyno sinks down in to the platform it can take away the gear clearance and put a side load on the bearings and destroy the insulating cups.
