The 650SS

Bernhard · Jan 3, 2013

Rohan said:
A 55 Manx would be less than competitive against even a 61 Manx.
Once Doug Hele got his hands on them, they improved, a lot.

What did they get out the 500cc Triumph that did so well at Daytona - 145 mph laps ?
And became the Daytona Model road bike, although not quite as fast in that guise...

by worntorn » Mon Dec 31, 2012 9:28 am
Rohan, that is what interests me about the Domiracer, the undeveloped potential of the bike, as well as its direct connection to the 650ss. Norton had developed the Manx for about thirty years and really had nowhere left to go with it. This was just the beginning for the little twin and already it was right there, nudging up against top riders on the fully developed Manx.”

True, the production 500 twin Daytona’s were not as powerful or as fast as the racer, but for a 500 they were road tested and still did 118mph.
There seems to be some confusion here as to the 500 Daytona not being able to beat a Manx Norton on the (short circuit) race tracks.
There was one guy, Dave Degens, who campaigned his 500 Triumph Dresda successfully for many years, frequently winning the Classic Bike 500 class & championship, much to the annoyance of the other race entrants, so much so, that when he decided to enter a 350 Triumph twin version in the 350 class, and which he won, ( of which he was entitled to do) there was an unbelievable uproar And resentment from some of the riders of that class.

acotrel · Jan 3, 2013

I suggest that whe you compare a 500cc dominator with a 500cc Daytona Triumph, you are comparing two completely different things. I don't know what the stroke of the domiracer was, but a Daytona has a 65.5mm stroke, and a hot one would be a nasty piece of shit. It is really difficult to get decent torque out put from a very short stroke motor, and I doubt that the Daytona ever had a six speed gearbox. On a big circuit, it would be great but difficult to ride well on a tight one. I suspect the Percy Tait Daytona 500 had the 1973 type crankcases with the ball race on the timing side of the crank. Nobody was going to develop a successful privateer Daytona 500 in the sixties without that. They are not a proposition today because they are the C type motor, and the gears from an A or B type don't fit, so you would have an immediate $6000 expense for a decent gear set. I saw a 1973 T100 at a big swap meet at Bendigo many years ago for $3000. I decided not to buy it, but it would have been a good starting point for a very fast bike. My own short stroke (63mm) Triton was pre-unit and used all 650 parts. It gave me a really hard time as it was almost impossible to ride well. I wouldn't go shorter than a 75mm stroke in those twin cylinder motors, unless I had a six speed CR box. ( A crank out of the short stroke Thunderbird could be a good thing.)

Rohan · Jan 3, 2013

acotrel said:
It is really difficult to get decent torque out put from a very short stroke motor, )

Quite so.
Torque comes from the gas flow through the head, and how well it fills the cylinder.
Not from how long the stroke is.

And, actually, one of the torquiest motors ever made was the Suzuki GSX1100E (short stroke) four - on the dyno, it put out MORE TORQUE DOWN LOW than a HD big twin of the same year - and that is really saying something. One of the flattest torque 'curves' you will ever see. AND revved to twice the HD revs, so made some serious power. It had Suzooks 4 valve 'twin swirl combustion chambers'. Sidecar and drag race guys love these motors - one piece cranks with plain bearings, so they don't twist, are cheap to rebearing, rev like the powers, and can take a huge bore oversize.

Boring, and rather ordinary bikes though, however good the motor is on its own...

Matt Spencer · Jan 3, 2013

Bernard " This bike was brought by Dunstall, prior to Norton’s moving down south from Bracebridge street. It was raced by Ray Prickell and became worn out. I am informed that Dunstall tried to sell it without success, and as the whole engine was virtually a one –off, it ended up in a skip, but I have been unable to confirm that last story.

Story in Mag re Dustall said he got seven van loads , anything he didnt get from race shop ' went in the tip ' . :shock:

Rohan · Jan 3, 2013

It also said a lot that came from the race shop was unknown stuff - no way of knowing if it was a tried, and failed, experiment.
Or if it was successful, and therefore a good idea or improvement...

acotrel · Jan 4, 2013

Rohan, The ratio of rod length to stroke has a big effect, as does inlet port diameter compared with capacity. If gas speeds drop too low, the motor becomes a 'top end motor'. It develops it's horsepower higher up the rev range. The exhaust system also affects this - two into one exhaust with the right exhaust cam timings is very important to get power lower down the rev range. If you build yourself a top end motor you have to always be 110% in your riding - most unforgiving and difficult to outride others unless the circuit is very big. A daytona with separate pipes, megaphones and a 6 speed CR box would be great fun, but you wouldn't get sound sleep the night before a race meeting. I raced my short stroke Triumph 500 for 12 years , and I sold it in about 1983. I don't want to see it again. Compared with that nasty bastard,my Commando based bike is a gorgeous lovely piece of versatile engfineering.

Rohan · Jan 4, 2013

acotrel said:
but you wouldn't get sound sleep the night before a race meeting.

Thats because the dudes in the truck next door brought a whole truckload of beer, and invited everyone. !!
Then someone tested their new megaphones at 2.30am, decided it wasn't right, had more beer, and tested them again at 3.30am. And again at 4.30am.

Maybe they should do night races, and keep the daytime for important stuff.... ?

Bernhard · Jan 4, 2013

acotrel said:
I don't know what the stroke of the domiracer was, but a Daytona has a 65.5mm stroke, and a hot one would be a nasty piece of shit. It is really difficult to get decent torque out put from a very short stroke motor, and I doubt that the Daytona ever had a six speed gearbox. On a big circuit, it would be great but difficult to ride well on a tight one. I suspect the Percy Tait Daytona 500 had the 1973 type crankcases with the ball race on the timing side of the crank. Nobody was going to develop a successful privateer Daytona 500 in the sixties without that. They are not a proposition today because they are the C type motor, and the gears from an A or B type don't fit, so you would have an immediate $6000 expense for a decent gear set. quote]

Re; I don't know what the stroke of the domiracer was, but a Daytona has a 65.5mm stroke, and a hot one would be a nasty piece of shit.

I get your drift, I was merely pointing out that Norton’s failure to developed their 500 Domiracer was a lost opportunity, and what the one and the same engine tuner, Doug Helne, on both engines, achieved with winning the annual Daytona road race on the Triumph 500 twin might have also achieved on the Norton twin a lot earlier if the Norton Dommiracer did not infringe the AMA rules.
The 500 Dommi has a 72.6mm stroke with a 66 mm bore, and I am a bit sceptical that was what was in the 500 Dommiracer motor, although it was claimed to have those dimensions. Why? Because it used a 650 Manxman cylinder head and I personally do not think it had a 72.6mm 500 bore, as opposed to a 600/650 82mm bore.
I have a 500 with a 650SS head and h/c domed pistons off a 600.

Re; It is really difficult to get decent torque out put from a very short stroke motor

No arguments there, but the full race 500 Daytona’s had a full race cam and would require revs (all a the top end) to keep the engine going, low power on the race track is not a primarily requirement (although it helps!)

Bernhard · Jan 4, 2013

Matt Spencer said:
Bernard " This bike was brought by Dunstall, prior to Norton’s moving down south from Bracebridge street. It was raced by Ray Prickell and became worn out. I am informed that Dunstall tried to sell it without success, and as the whole engine was virtually a one –off, it ended up in a skip, but I have been unable to confirm that last story.

Story in Mag re Dustall said he got seven van loads , anything he didnt get from race shop ' went in the tip ' . :shock:

Yes, that story was as I read it, so, does anybody actually know exactly what happened to the 500 Domiracer motor :?:
This is the one with a Specially made Alloy barrel and eccentric valve adjustment.
To quote Dunstall on the 500 Domiracer, “nothing from a standard Norton would fit as in this engine there was not a standard nut or bolt”

acotrel · Jan 4, 2013

I completely understand what you are sa ying about the Domiracer being a lost opportunity. I would have love to have seen Norton produce a cheap production racer, however a Triumph was always going to beat it. When you build an exhaust system for a racer, you usually end up adjusting the cam timimg to suit it. The Norton twins don't have separate inlet and exhaust cams, so the job of optimising is so much more difficult. With a Triumph engine there are vastly more options as to which cams and timings you can use. I spent 12 years playing w ith cam timings on my 500, and I know the effect it has when the cams are moved in various directions. The exhaust opening point is the most critical, and on a Norton motor if you change that, all the other lobes move . It is then not simply a matter of removing a cam wheel and adjusting the inlet cam, you have to split the cases and fit a whole new camshaft. The domiracer had potential because the Norton motor has good torque characteristics , but a well developed top end motor with a 6 speed box must eventually perform better e.g. the Paton, and the Daytona engine could get there too. The other thing about the domiracer was the featherbed frame. The next generation of frames turned up soon afterwards , and some guys built 'Tricatis' using the 250 Ducati frame with the 500cc unit triumph motor.

Rohan · Jan 4, 2013

acotrel said:
The exhaust opening point is the most critical,

On Manxes and Inters, its the inlet cam you mostly alter the timing of, to suit the exhaust in use....

acotrel said:
The Norton twins don't have separate inlet and exhaust cams, so the job of optimising is so much more difficult. It is then not simply a matter of removing a cam wheel and adjusting the inlet cam, you have to split the cases and fit a whole new camshaft. .

Some domi engines had the whole cam system as a complete bolt-in system.
Quite how the cam followers handled this though ??

Rohan · Jan 4, 2013

Bernhard said:
Yes, that story was as I read it, so, does anybody actually know exactly what happened to the 500 Domiracer motor :?:
This is the one with an Allot barrel and eccentric valve adjustment.
To quote Dunstall “nothing from a standard Norton would fit the engine there was not a standard nut or bolt”

Ben covered all this in a previous post on exactly the same subject. ?
Be in the archives....

acotrel · Jan 5, 2013

Rohan, Even if the camshaft was replaceable without splitting the cases, you end up with the same problem you have with a piston ported two stroke. The best port timings are asymetric, and you need to be able to adjust inlet and exhaust independently. It is one of the reasons that I didn't race my Seeley Commando until recent times. You are always tied to someone elses work in developing decent cams, unless you are prepared to endure the pain of grinding your own every time you want to adjust the relationship between exhaust and inlet. With a Triumph engine, these days you have huge choice of cams, and easy adjustment to suit your engine's needs. If you want to develop a really fast big twin motor, you should start with a Nourish Weslake, not a Commando type engine. It will work out cheaper.

Rohan · Jan 5, 2013

There are plenty of good cam 'race grinds' for Commandos out there - pick one and go racing ?

This thread is supposed to be about the 650SS.....

worntorn · Jan 5, 2013

Acotrel recently wrote:
"That leaves the Norton Commando in the same market niche, a reasonably priced, functional bike that is totally rebuildable and responds extremely well to tuning. ."

But more recently wrote:
" If you want to develop a really fast big twin motor, you should start with a Nourish Weslake, not a Commando type engine. It will work out cheaper."

Acotrel, I thoroughly enjoy you posts, but you are giving me whiplash man!,,

Glen

Rohan · Jan 5, 2013

You mean there are not 3 folks who (randomly) post here all using the same handle ??

Triton Thrasher · Jan 5, 2013

Rohan said:
acotrel said:

The exhaust opening point is the most critical,

Click to expand...

On Manxes and Inters, its the inlet cam you mostly alter the timing of, to suit the exhaust in use.. ??

Hmm. Depends what you mean by "most critical." If you want to lose tractability and gain something at the top end, the way to do it is to retard the inlet closing.

Matt Spencer · Jan 5, 2013

" " If you want to develop a really fast big twin motor, you should start with a Nourish Weslake, " "

This Fugly lump looks close enough , apart from being wider in the bilges than the Queen Mary .

IF someone whis up a decent set of Pre Unit crankcases for one , we should be able to pass it off as a Weslake ,
admirably .

as long as they leave all the drivle of the ends , down there . & close in whats necesary .

looks wider than a whizz bang . Thought the advantage of a TWIN was its NARROWNESS . 8) :mrgreen:

Matt Spencer · Jan 5, 2013

Now , meanwhile . Back at the Ranch .' Raceing all my life ' Derek Minter . 1965 .

" for machines up to 1000cc - for this I was entered on the works; 650 Norton Twin .

was able to overtake Mike Hailwood. I was able to hold the lead , to some extent by vitue of
my powerfull machine , throughout the remaining eleven laps "

" while another ( motorcycle weekly ) one reported that my appearance on the 650 Norton was most impressive ,
for the roadste-engined machine had blown Mike Hailwood's super fast 500 right off the road . "

Brands . Good Friday . 1962 .

worntorn · Jan 6, 2013

Good stuff, Matt!
That would be Hailwood on the MV Augusta 4, the one that slaughtered Manxes and ate G 50s for breakfast?
Glen

The 650SS

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