650 SS Head

On the off chance that ML knew something I didn't, I checked some 'facts'.
Bert's book "Whatever happened to the british mc industry" gives a good rundown of his whereabouts.

Maybe the said problems happened to BSA, while Bert was at BSA ??

Or, we have seen some odd rockers for early Nortons twins, maybe Nortons had problems without Bert ?
Bert had enough troubles with the design of the dommie inlet tract, and oil leaks from not enough screws in the timing cover....

But we digress from 650SS heads, although they are made of alloy, and these are their ancestors.

Rohan said:

Bernhard said:

you may be right on the holes on the Atlas head, but you are misleading everybody who may be contemplating fitting an Atlas head onto a 500 twin, for a start a 750 has a bigger bore to the 500, so that the spigot of the 500 will be way undersize to the 750.

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No I'm not. For anyone silly enough to actually contemplete doing this (why would you, 4:1 compression ??!), the later Atlas heads are spigottless - so you'd have to machine off the 500 spigots, to match. From there, its nearly a bolt up fit. Apart from the 4 bolts that don't line up, that is. This is without investigating what the valves would be doing either...
The point was that the bolt dimensions had not actually changed that much between early 500 dommie and Atlas.
Surprising little, in fact, to me anyway.

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To Rohan, I was not suggesting that you were giving the OK for anyone to fit an Atlas Head to a 500 twin, I was merely trying to prevent anyone who has not got the correct knowledge from getting the idea from this website that you could do it-misinformation is rife on the internet :!:
No sooner had my last comment been printed when someone comes up with information that someone else had fitted the Atlas head to a 500 twin.
No doubt it is possible, if you blank the holes up in the Atlas head and re-drill them to fit the 500, also alloy weld up the spigot in the head and recut to fit too. You are then left with having to recut the valve cut-outs in the pistons, for the larger valves.
After all, the last production years of the 500SS had a splayed exhaust ports and downdraught inlet ports just like the 650SS. There was probably no difference between them, except for the drilled holes and bore diameter.

I saw a beautiful 650SS for sale at Central Motorcycles, in Huntingdale (suburb of Melbourne) two days ago.

Bernhard said:

if you blank the holes up in the Atlas head and re-drill them to fit the 500, also alloy weld up the spigot in the head and recut to fit too. .

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For anyone actually thinking of doing this, the majority of Altas production (ie ALL the later ones) were spigotless, so select a later head and forget about welding anything.
Could probably just enlarge the bolt holes in the Atlas head too, they are not far out, no welding needed there either. ?

Unless they were thinking of racing it, using Atlas parts under it will give a lot more go than any 500 will offer though .. !?

Thought we'd throw in a pic of the head design earlier than a 650SS, to see where this design came from and evolved from ...

This is the pic in the Dommie 500 owners manual, issued circa 1949 with the first Model 7, 500cc - all iron head (and cylinder).
As you can see, the inlet part has a strange design, with a slightly bifurcated port design in the inlet tract. Single Amal carb, of course - as all early dommies had.
This was apparently none too successful (ie very slow ), and this was subsequently amended to a pair of inlet ports, and a little u-shaped alloy manifold strung between them.
Bert Hopwood left Nortons in a huff over this - he claimed (in his book) that Joe Craig (Nortons Racing Director) had unnecessarily interfered in HIS design.
Bert had designed an earlier BSA twin with this style of port - longstroke small bore twin thing, maybe it didn't notice it was slow...
Subsequently , late 1950s, Norton head got twin carbs, and then the downdraft ports of the SS heads in the early 1960s.

There endeth the history...

P.S. If anyone has seen a head like this, out on the road (or in a museum) we'd be interested to hear.
There is some debate about whether any were actually sold like this.

I've got questions about Bert Hopwood and Val Page. The aerial single was a great bike. The BSA A10 was horrible as was the iron top end dommi. What were those two blokes about - company men ?

I've got questions about Bert Hopwood and Val Page. The aerial single was a great bike. The BSA A10 was horrible as was the iron top end dommi. What were those two blokes about - company men ? I've still got old Motorcycle, and Motorcycling magazines from back in the fifties, and I can remember the exasperation we had at the underpowered and bad handling garbage bikes we were offered back then. Some of them resembled motor scooters, none ever resembled a Morini or Parilla road racer, - and we didn't even know about THOSE. A 350 Aermacchi Ala D' Oro was ten times the bike a 350 manx or 7R ever was. Who bought them ?

You should have said something then, 60 years ago ?!!

I had a plunger frame all iron engine dommie as my first road bike, some years after it was new.
Wasn't so bad, when it was new ? Very pleasant and relaxed ride, and sporty even for its day. Stylish even.
(although it was more a POS when I got it !) and better than a lot back then - still got it, and a few others.
As I like to quote, at 440lbs is 40 lbs more than a Commando, and half the horsepower. !
And there was that cachet about "built in the light of experience", although I could never see any connection with the manx race bikes.

You have to remember too that post-war Britain was a very tough place - debt debt debt, steel was rationed, petrol was rationed.
And British bike manufacturers tried (desperately) to lightly improve what they had, rather than do a whole new design.
For them, a dommie twin WAS a new design.
Even if they initially kept about the same chassis and wheels and brakes etc etc etc.

As for your 350 Aermacchi Ala D' Oro (Gold Wing), they weren't even faintly competitive until 1963 or later.
By which time Manxes and 7R's were going out of production.

They perhaps should be rather viewed as taking over the mantle, where the manxs and 7Rs had left off.
They had ceased to be truly competitive some years earlier, if you even glance at the results sheets...
As is often the case in racing, few remain at the top forever....

Nothing to do with 650SS heads though....

acotrel said:

ML, Unusual for Rohan to get something so important, so wrong . Perhaps you should check your facts ?

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1950 ISDT experimental twins, 4 bikes prepared with alloy heads. The event was in September, design and production committed to in late '49.

Bert started with BSA in May 1949. (After taking a "long holiday in Devonshire").
Thats a long way away from the 1950 ISDT.

The Model 7 was barely in production by then.
Be interesting to know how many they had produced by then, in fact... ?

Rohan, a 1963 Aermacchi was only one year later than a 40M - makes it look stupid. I know the British had a hard time post WW2, so did the Italians. Yet have a look at the design differences . What brought the Italians undone was their metallurgy and electrics . Have you seen the video of Guy Webster's museum in America on vimeo ? It was British managers who were populist, trying t o catch up with the trend's and satisfy the duffle coat and desert boots brigade, instead of doing what they did best.

Rohan, a 1963 Aermacchi was only one year later than a 40M - makes it look stupid. I know the British had a hard time post WW2, so did the Italians. Yet have a look at the design differences . What brought the Italians undone was their metallurgy and electrics . Have you seen the video of Guy Webster's museum in America on vimeo ? It was British managers who were populist, trying t o catch up with the trend's and satisfy the duffle coat and desert boots brigade, instead of doing what they did best.

http://www.youtube.com/watch?v=mADiAdBdC24

http://vimeo.com/3895328

http://guywebster.com/photos/show/553

acotrel said:

What brought the Italians undone was their metallurgy and electrics .

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Italian casting was at some stage renowned as among the best in the world - Campagnolo and Ferrari etc in particular doing some amazing stuff.
I have wondered where Nortons got some of their alloy cast - the Z plates in Commandos in particular, they are beautiful.
An Italian bike I had had mostly bosch electrics, and that was a while ago, so maybe they learned something somewhere back then. ?
Never heard of an Aermacchi doing well (winning !) in the IoM TT - but maybe thats a subject for another thread another time.

Back to 650SS heads...

Aermacchi 350s have won a lot of classic TTs. They arrived in about 1963 just as the two strokes took over. Notably, a while ago our Bill Horsman won the IOM Classic TT on one. He was told that he should have been there years ago. He was one of those guys that if you saw him on the grid beside you, you knew it was probably time to go home.

As for Italian casting, their pattern making has always superb, their metallurgy often let them down. A simple example is the chrome plated tips on the rocker arms of the 250 Ducatis, - only idiots would do that. We had one break off during a race and crash the bike. It cost us a bomb in 1963. Most unrestored Italian bikes are a pile of rust, where they used to be plated. Obviously Ferrari use a bit of nous. You would expect that considering the price, and they'd have soon be finished if they had worked to the standards used on their 60s bikes. When I visited the Ducati factory, I noticed that Magnet Marelli was close by. ARRGHH ! ! Compared to them Joseph Lucas was Rolls Royce.

More (uninformed) rubbish ?
Chrome has nothing to do with casting quality - more to do with how much nickel they put under the chrome.
Having owned Italian bikes, I rather suspect they didn't use any nickel ?!
But then how many Italian makers made a profit in the decades around the 1970s.

The fuel cap on my guzzi rusted the first time it saw rain.
Kept it well oiled after that...

Were the rocker tips plated, or welded with stellite ?
Plating things is an effective way to prevent various heat treatments affecting the metal underneath, of course...

When the Aermacchis arrived in about 1963 they made Manxes look silly because Nortons had sat on their corporate backside, persuaded too possibly, by Joe Craig. Joe Craig may have been (almost certainly was) a brilliant development engineer, but he was no Design Engineer. Doug Hele demonstrated what could be done with his Domiracer, which may have had some impact on the 650SS head, and subsequent Nortons.
cheers
wakeup

Joe Craig had left in 1954, so not everything can be sheeted home to him !?
Doug Hele had done improvements to the Manx, splined bevel shaft and coarse pitch bevels amongst them,
so was not unaware of the problems.

But Nortons had no money, and several designs of inline 4's hadn't made it even to the prototype stage.
Joe Craig also supervised a laydown engine design of Manx, ala the successful guzzi singles, but it didn't get far off the drawing board either.
It was reportedly quite an improvement, but was never tested in action.
10 years later, Aermacchi came along with a similar machine, and took up where manxes had left off... ?

Nortons was simply a very small company, with a VERY small race budget by modern standards, so competing with some of the big factories of the time was an amazing achievement, but was never going to last. AMC's takeover and subsequently curtailing their racing activities didn't boost their wins either - (Joe Craig left at this point). And motorcycle sales slumped in the 1950s, so falling revenue didn't assist matters either.

Dunno what this has to do with 650SS heads, other than that was one development project that paid dividends, in terms of road performance anyway...

'But Nortons had no money, and several designs of inline 4's hadn't made it even to the prototype stage.'

A while ago I mentioned the lack of a Marshall Plan for post war Britain, and this was denied. Yesterday I watched a documentary on the Morris minor and the Mini, and the lack of funds for rebuilding their industry was mentioned again. That wartime and post-war relationship between Britain and the US was very strange and I've read a bit questioning Roosevelt's motives and attitudes towards the British Empire. The assertion was made that there was intention for the US to capture the trade areas in which the British had previously dominated. What is really strange, is that in spite of everything some parts of British industry really excelled, and today the F1 teams, the kit car industry are great. Also some of their defence equipment is excellent.