What’s a Don Wilson disc Tony?
You’ll have noticed the QLD single seat mods... I think that particular registration format has led to more bodged old motorcycles than just about anyone could imagine!
I’ll start a resto thread today or tomoz and I can have a whinge about some of its other qld’er problems... 
Don Wilson was the all time Australian guru of all things airhead. After a long time working for the biggest Sydney dealer and then after that as "troubleshooter" for BMW (Australia) Don set up his own business servicing, repairing, buying and selling airheads.
The problem with BMW brake discs is that if you want decent brakes you have to run sintered metal pads, if you run sintered metal pads you wear the discs out so fast it will make your head spin. even if you do not prematurely wear your discs out, the blasted things are prone to cracking, at which point they are a throwaway.
Don discovered that one of the local Sydney councils were renewing the manhole covers, storm water and sewer access covers as these 100+ year old cast iron covers were not made accept the weight of modern vehicles . He then discovered that the covers were made out of Meehanite cast iron, one of the very best forms of cast iron around.
https://en.wikipedia.org/wiki/Meehanite .
Some research led don to realize that the meehanite "variety" of cast iron was perfect for disc brakes and that after 100 odd years of "stress relief" the swapped out covers were just begging to be turned into brake discs.
So, he went to the council and bought the bloody lot and then contracted an engineering firm to turn them all into airhead brake discs.
Compared to the cost of the BMW disc they were an absolute bargain, I think from memory he sold the cast iron discs for around $AU50 plus freight/post. They came with instructions to grind off the base of the rivets holding the BMW discs to the carrier, how to drive out the rivet and came with a bag of high tensile button headed bolts to secure the new disc to the carrier.
Compare to the predatory price Metal Gear charge for their (admittedly very good) product, for some reason they charge more than double for an airhead disc than any other bike and they require you to send your old ones in for exchange.
Anyway, Don's discs handle sintered pads just fine (I have a pair fitted to my R100RS in about 1984 still in perfect working order) and the disc fitted to my 1984 R65 (before I fitted a K100 front end to it) was also a Don Wilson disc.
The only drawback, as you will already be aware of, if that they rust. In fact leave your bike out in the rain unused for a few days and the rust will all but prevent wheel rotation and the first stop is a doozy.
Anyway, that's the story of the "Don Wilson Disc".
Re QLD former single seat rego rules, yes they resulted in the disfigurement of thousands of innocent motorcycles. Worse the details of the plate affixed to the frame remains on the permanent TMR record, although TMR have indicated that as the legislation that underpinned the "modification plate" has now been superseded, they will not enforce it providing the bike is equipped and registered appropriately, i.e. you can have the original seat and fit rear footpegs PROVIDING the bike is no longer registered as a single seater.
The new TMR doctrine is much much better as it essentially amounts to "take the rear pegs off, tell us you have done so and we will register as single seat".
For bikes as old as ours there is an even better alternative - red plates. The Special Interest Vehicle Registration Scheme ("SIVS") was until recently of little, if any, interest to motorcyclists in QLD as the rate was fixed the same whether the "Special Interest" vehicle had 2 or 4 wheels - single seat rego was cheaper.
BUT, that recently changed and you can have SIVS rego for $172 per year and they don't care if you are single or dual seat. The bike must be over 30 years old and you must be a member of a motorcycle club approved by TMR and have a letter from a management member of that club attesting that your membership is current, and where applicable, the age off your bike (not relevant to any BMW made since around 1968).
There are restrictions on when and how far you can ride your red plated bike - you must either be:-
1/. Going to or from an "event" set up by a recognized motorcycle club.
2/. Test riding within 10km of your home
3/. To or from a place were "work" was performed on your bike or obtaining quotes for such work.
Really all that TMR want to do is stop people using Red Plated bikes as "daily drivers", they are quite open to innovation. My club recently put the following proposal to TMR. -
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