Yes, nice looking bike!!
I would surely not repaint it. Go over it with some oil and keep the charisma it has now.
Or alternatively try to remove only some of the light green paint, looks like aerosol paint to me.
You have only one change to keep this look. with a repaint it probably turns into just another M20....which is also very nice, but.........
Good luck from the Netherlands!
Rebuild it, get everything within the correct tolerances and working properly, repaint and replate it to preserve it properly and then enjoy a couple of decades of reliable performance before you have to do it again....
or don't restore it, but never be sure about which worn out bit is going to give up next and watch it corrode as you ride it over the next couple of decades.....
Between the breakdowns you can sit back and admire the rust..sorry ...patina...
....Ian
email (option): ian@wright52.plus.com
Sorry Ian, you are not representative on the rust issue, riding all day through mud, rain, snow, salt and ponys with your M20 as main transport
Off course the bike should be totally rebuilt mechanically to prevent breakdowns but it won't rust away if the older paint is preserve in the right way.
Oil, grease and rustprotectors like Tectyl goes where newly applied paint won't go. Like mudguard seems, inside the tubes of frame and forks, inside the hollow parts of the rims, around nuts and bolts where it seals off the damaged paint when they are being fastened, etc.
The bike doesn't look rusty now, and think the bikes will not rust away when using them occasionally as that forces you to work on it quite often. They rust when riding throught salt in winter and putting them away in damp sheds for longer periods.
But I have found that it is really difficult to preserve the old paint during rebuilt as it is easily damaged by the need of using heat or force. At such moments the drive to totally repaint it is attractive but that could be regretted later.
There is even a great change that the dark green on this particular bike is the original, very durable, paint.........
email (option): m.wijbenga[at]hotmail.com
I know the two views on whether to restore or not will never be reconciled and supporters of each view are unlikely to change their position...
As Michiel has noted I always look at it from the point of view of how best to achieve a reliable bike that can be used at anytime of the year...To my mind that is what they are for...
I don't really see the point of covering a bike in oil or anything else if the paint is no longer up to the job of protecting the metal...
The corrosion is how you know it's time for a repaint!....
My views on preserving so called 'history' at a completely arbitrary point in time are well known...
If you argue to preserve a bikes history in its entirety the logical conclusion of that argument is that you don't touch anything...even later incorrect paint, incorrect parts etc...All of that IS part of the bikes history...
If you start to preserve history on the basis of what you like and what you don't then you are meddling with it and altering it anyway...
I've always said for example...the three rebuilds that I've done on my own M20, that were required due to a lot of use during the time I've owned it ARE part of its history...
History, in fact, is not a static thing but moves on every time someone does something...You can't actually stop it or preserve it unless you put your bike in a heated garage and don't touch it again... ...
That, to me, is also an alien concept for a machine that was made to be used and can still carry out that function....
I guess now I will also have upset all the museum curators and collectors as well....However, it's only my view of the world...Ian
email (option): ian@wright52.plus.com
It probalby all depends on the quality of the existing paint and cannot be judged from a picture.
But to my opinion, if the dark green is applied during a National Service postwar rebuild, it certainly deserves a change to preserve it.
My main point is not to make the decision of a repaint/replate too quickly in the excitement of the start of a rebuild as it can not be returned and can be much regretted.
You could also postpone the decision by taking it apart, rebuild its components without touching the paintwork unless really necessary. Put everything together again, do some test rides to make sure everything is mechanically fine, take it apart again for doing the paintjob or preserving the old paint.
Good luck, 
email (option): m.wijbenga[at]hotmail.com
Back in 1976 I acquired a Norton 16H. It had been sold off by the army but had never been used by the army ie kept in the stores in a crate. The guy who had bought it in 1948 had never used it after riding it home. When I bought it in 1976 from his estate the mileage was just 64 miles.
My point is that despite being in a heated garage and never used for nearly 35 years the original paint (yes it was original) had deteriorated to the extent that just touching it caused it all to come off just like dandruff! Now another 40 years later I refuse to believe anyone when they say their paint is the original from when the bike was supplied.
This means that if, as no ones paint is original then it doesn't matter what paint you use or process or the colour (within limits of course) as once the original has gone its gone for ever.
Bikes repainted in service may well still have some of that paint on them, but it's still not the original. I believe that when bikes where repainted it was applied a lot thicker and using different types of paint and therefore in some cases has lasted longer.
At least the bike doesn't need the paint to function mechanically...though I agree with Keiths sentiments entirely...
These 'unrestored' bikes out of barns are all very well but the fact is you don't know the condition/state of wear of all the parts...
This is a recipe for unpredictable reliability if you use the bike...Frankly, I wouldn't want to be hundreds of miles from home on a bike that I wasn't confident was in the best possible condition to get me there and back...
Once a bike is rebuilt, you pretty much know what the 'state of play' is with all the wearing parts and can realistically assess on an on going basis when they will next need looking at as part of your maintenance programme...
The challenge of riding/travelling on these old bikes IMO is not to have to get your tools out at all when out on the road and the work done in the workshop both during and after a rebuild is the best way to achieve that...
Of course if what you want to do is potter about locally now and again during the summer months and you trailer the bike if it's further away, you may well get away with it....
The fact is the description of 'motorcyclist' as I understand it, where you take the bike as a first choice most of the time just for the enjoyment of using it, is rapidly becoming a thing of the past.
That in turn means the minimum reliability standards that I look for aren't really needed in many cases...
So, at the end of the day, how you prepare your bike is less about what you think of the more esoteric aspects of history, patina etc. and more about how you actually intend to use the bike.... Ian
email (option): ian@wright52.plus.com
Jeff actually said he thought the trend towards,or perhaps the look of, fake patina was refreshing... (as opposed to 'over restoration')....
Personally I particularly dislike the fake patina trend...
If you want patina and you haven't bought a vehicle that has it, then put some miles in all the year round and you'll have some of the real stuff after a few years..
I have 'patinised' two of my bikes after full rebuilds to such a degree that they have both needed rebuilding again.. (I have owned them for 29 and 34 years respectively)....That's how it's supposed to be done and it's just a cycle these bikes go through endlessly, unless they are scrapped......
Regarding the paint there's no point repainting it if the paint is sound and it doesn't need it....
I am arguing more that the paint is there to protect the base metal as well as to look nice...When it doesn't do the first of those two things the solution is not to get out a paint brush and a tin of old sump oil....The solution is to repaint it....
I really cannot understand peoples enthusiasm for half worn out motorcycles covered in oil...
They weren't like that originally you know...They got like that through neglect and/or hard use..and what's the point of preserving neglect and voluntarily putting up with the detrimental effects of hard use?...
If anyone wants to build a bike like that I have a pile of worn out bits they can have...Ian
email (option): ian@wright52.plus.com
Have to agree I dont like the fake patina trend I misread Jeff s post, If you have a bike with patina though it doesnt have to be half worn out or even a little worn out I have proved that with the B33 I had it was just as good as any restored bike and in a lot of cases better just didnt look like it.Most old bikes get their patina from being used which proves they actually are a working machine unlike some restored bikes which maybe look the dogs nads but are worn out wrecks that have been made to look the part some people are good at making there bikes look right but dont have a clue as to there mechanics and have no mechanical ability but can send parts off to a powder coaters and buy shiny repro crap which is then bolted on said restored machine ,usually these bikes are so called finished then sold off on sites like Ebay stating totally restored just need tuning/carb/timing setting up or the thing doesnt actually charge and I dont have the time to finish..NO you dont have the ability!! I give my own bikes a hard time and use them all year round and my own WM20 is now getting a nice patina after 7 years use but is also getting to point where it will need work on it soon.. As for your pile of worn out bits Ian put them on Ebay maybe help someone with there restoration Dave
The bike I mentioned that I have owned for 34 years is a 1951 rigid B33...a brilliant bike that has taken me to work, all over the country on holiday, club runs etc.....
I bought it originally for £60 from behind a blokes garage where it had sat under a tarpaulin for 9 years...
It was suffering from 'extreme patina' so had to be rebuilt...
Over the years it has been immaculate, not quite so immaculate, dog rough, immaculate again and at the moment not quite so immaculate...Ian
email (option): ian@wright52.plus.com