750 Atlas Drag Test

I've been cleaning out some of my old magazine accumulations, and ran across this "Drag Test" (really just a road test) from the September 1965 issue of Custom Rodder magazine. Kind of interesting to see how the hot rod car guys wrote it up back then.













Ken

If you watch Duke Video's 'The Right Line' I believe you will see Don Rickman on a Triumph engined Metisse going very well. However I always had the impression that single cylinder scramblers such as Geoff Clew's 'Clewstroker' were a better option before the two strokes took over. I've always liked those Matchless framed Norton Twins, I think we could d o ourselves a great big mischief with those.

60 HP???

I want one!

Norton claimed 60 hp from most of their 750cc engines ?
The 650 had been called 52 hp, so 750cc must give more, right ?
Brochure hp, remember.

Note also that that is not an Atlas, but an Atlas Scrambler.
Altas type engine, but in the Matchless frame. But Norton forks and wheels.
Later it would be called the N15CS, and then the P11 and P11A, with various changes.
Same beast, different clothes....

Anyone seen any footage of the Paris-Dakar races of more recent years ?
These desert racers are the ancestors of some of those things - the KTM 990cc v-twin thingies that would do 200 km/hr (125 mph) though the desert, before they limited the capacity the last few years to 450cc.

Thanks Ken, interesting stuff !

Re comment “I was really disappointed-it was too smooth” unquote;

A ridgedly mounted Atlas engine “smooth” :?:
What planet was this guy from :?:

Planet 1965 , yeah baby 8)

Bernhard said:

Re comment “I was really disappointed-it was too smooth” unquote;

A ridgedly mounted Atlas engine “smooth” :?:
What planet was this guy from :?:

Click to expand...

Other tests of N15CS and P11 have mentioned the less vibes than in an Atlas ?
Different frames, different vibration characteristics ??
Could be as simple as how different mudguards/fenders are mounted, etc.
And high v's low handlebars, etc.

Or, different Balance Factors ??

I had a 62 Atlas which was advertised at 52 HP. It had a single carb. My 63 Atlas came with dual carbs and was advertised 60 HP. It very definitely had more push than the 62! My brother had a 65, also advertised at 60 HP, but my 63 would walk away from him at any speed and gear selection. His 65 was definitely more tractable than my 63. He could ride 4 th gear down to 25 mph, but I had to shift to third below 35 mph. It always made me wonder if my 63 had a hotter cam and was a beta model that the Berliners were market testing. The 63 was purchased from a dealer located near the Berliner importer.

I still have the 63!

Interesting.
"Hey Joe, anyone seen that Atlas with the special setup I had here."
"We sold it".

Atlas's and 750's had several different Amal carb setups listed in several years, maybe some were better than others ?

Some of the 650cc models had those little inserts in the inlet ports (to boost tractability ?), did any of the Atlas models get them too ?
When did Atlas's stop using the dished crown pistons ?

Cycle World tested a featherbed Atlas with twin carbs in 1963 and it did an 89mph quarter in the mid-14 second range. The previous year they tested a 650 Manxman and it did about the same.

In 1967 Cycle World tested a Norton P11 Scrambler that had the 30mm Amals and 7.6:1 compression, and predictably it did the same in the quarter, 89mph at 14.6 seconds.

But when they tested their first Commando, with it's 8.9:1 compression, it went 13.46 at 96 mph even though it was geared higher and had a tested weight with rider and fuel of over 150 pounds more than the P11 scrambler in the 1967 test.

I have run both a Commando and Dominator in factory standard trim down a quarter mile dragstrip and got almost identical speeds to published road tests.

Norton 750s never had the inlet tubes, that was a 650-only part. Norton 750s did not have "several" carb setups, they either had one or two 1 1/8" monoblocs or two 30mm concentrics.

The Atlas did have bigger inlet valves than the 650. The Atlas always showed low compression in factory literature, and in the parts books the only time I saw a change in it's piston part number was when all Norton piston parts numbers changed, when the cylinder spigot was eliminated along with it's matching recess in the head, this showed a published compression change of 1/10 of one point.

After 66 the Atlas got 30mm carbs just like the Commando would get, and it if had the same compression then they would test at the same performance in acceleration and top speed, I never saw this in any period magazine tests, if someone has one lets see it.

Except for the compression, primary drive, rocker oiling and intake manifolds, the Atlas and early Commando engines were the same. The only thing that made the difference in performance was the large boost in compression the Commando received.

Although the 650 had smaller carbs, valves and ports, it's 9:1 compression let it run as fast as the 7.5:1 compression Atlas. So there is a lot of published test data that shows how important that 1.5 points of compression is to the Norton twin engine......

beng said:

Norton 750s did not have "several" carb setups, they either had one or two 1 1/8" monoblocs or two 30mm concentrics.

Click to expand...

The factory lists for the Amal setups for various bikes over the years shows monoblocks with either 350, 400 or 420 mainjets, 3 or 3.5 slide cutaways, and these are listed against individual years.

So that would seem to suggest that not all amals were all the same for all years, no ??
The difference could well be aircleaners, or mufflers, or ignition system, or the phases of the moon, but that sure reads as different setups for different years....

Found another old mag with a road test in my archives, April 64' Cycle World tested a N15 scrambler and got 90mph at 14.4 seconds out of it.

Norton changed the jetting over the years, as anyone would that messed around with exhaust and air cleaner types, but the choke size of the carbs was only changed once, when they changed to concentrics.

From the road tests it can be seen that nothing changed the performance of the Atlas, featherbed or scrambler, over the years it was sold to the public. All we need now to make this thread complete is a period test of a Dunstall Atlas that shows a quarter mile effort.....

I noticed that the bike in the test Ken put up is the same type as in the April 64' Cycle World test. I doubt if there are any of these left laying around in standard trim.

This bike was from the West Coast distributor ZDS motors, and they said this is how it was supplied new, with no mufflers, a knobby rear tire and non-folding footrests. The article said that his early scrambler was also the last batch to have the narrow 7" front forks. Also on the bike are chronometric instruments. Notice the single rib on the front and rear fenders.

The frame on these bikes was really heavy, Matchless came out with it for 1960, the 59' and earlier single downtube frames had a problem where the downtube broke below the steering head when AMC started stuffing parallel twins in them for USA marketing/consumption.

They solved that problem by making what might be the heaviest British "scrambler" ever. By 1964 pros were switching to two-strokes or light custom frames like Cheney or Rickman etc.. Only in America could a poorly managed and bankrupt company find a home for 7000 of these.

Awful lot of ' experts ' here ! :x
'Unloading for a ride in the Mojave Desert - 1964'


What Jap trash was available in 64 that wouldnt fall to bits , & would do the Ton in the Desert ? ring ding or other .



Wouldntve been as well made , durable , or reliable as a good Triumph , back then . " The Worlds Best Motorcycle " . indeed .



When Men were Men , and Woman knew it . :lol:



those were the days . http://www.flickr.com/photos/bcgreeneiv ... otostream/ desrt triumph photostream .

Well, I know this is not official road test procedure, but I once timed my 63 Atlas 0 -60 as follows: my cousin placed himself 100 yards down the road with a stopwatch, and when he dropped his arm, starting the watch, I burned out of the hole. When the chronometric jumped to or past 60 I gave him a hand wave to stop the watch. We did 4 runs as I remember (it was a half century ago), but I recall an average et of 4.8 sec., a little better than claims above, but subject to much error, I'll admit.

The performance of my 62 (which by the way I bought from Sal De Feo mentioned in the road test article), was disappointing . It could take my buddy's 650 beezer, but those extra 100 cc's should have done more than edge him out. I guess that is why I quickly traded it for the 63. The performance difference between my 63 and my brother's 65 was too much to write off as minor carb or timing differences. He weighed the same as me, and his Atlas was new and little more than broke in. When I say I could "walk away" from him, the distance between the bikes would increase like one human walking away from one standing still....pick any speed & gear...same result. If I had bought the 63 used, I would have insisted the previous owner had cammed it. The tractability issue adds some credence to that.

Given that the Berliners knew Americans wanted power, and that 62 & 63 Atlas's were all exported to the US, could it be that Norton delivered 63's in a higher stage of tune, then dialed it back to improve tractabilty in 64 and later years as they began to fill the European market? Any gurus out there who might know?

I am planning to replace the 10.5:1 compression pistons I installed in the late 60's (all facts stated above were with stock 7.5:1 pistons). That would be a good opportunity to time my camshaft. Anyone have a link where I can get timing and valve lift data?

By the way, those high comp pistons increased the vibes as well as the push....with the Atlas idling on the center stand, it would "walk" itself along...but backwards!

About the bike being 'too smooth'. I've always had the impression that single cylinder four strokes give more drive on dirt than either four stroke or two stroke twins . And Vincent engines are better in speedway sidecars than four cylinder Japanese engines. On dirt it is always a balance between slide and drive ?
You guys should try this:


http://www.youtube.com/watch?v=wGbYoU1i8wg

texasSlick said:

Given that the Berliners knew Americans wanted power, and that 62 & 63 Atlas's were all exported to the US, could it be that Norton delivered 63's in a higher stage of tune, then dialed it back to improve tractabilty in 64 and later years as they began to fill the European market? Any gurus out there who might know?

Click to expand...

Cycle World's 63' Atlas with twin carbs ran exactly the same as all other Atlas bikes ever tested in the 60s, did you read that above?

A bigger cam in a 7.5:1 750 Norton would not make it run faster at every speed in every gear, it would more than likely run slower! Anyone that knows anything about engine tuning will back me up on that. The only thing that improves power at all rpms like that is a smart application of higher compression or some really intelligent head porting, which did not exist in the USA in 1963!

texasSlick said:

I am planning to replace the 10.5:1 compression pistons I installed in the late 60's (all facts stated above were with stock 7.5:1 pistons). That would be a good opportunity to time my camshaft. Anyone have a link where I can get timing and valve lift data?

Click to expand...

The camshaft timing of all Norton 650-850 twins from 61-onwards was the same, they all had the same grind camshaft. It started out being the 650 cam, then was called the SS cam when it was stuck in the SportSpecial 88,99 and 650ss bikes. In 63' on nothing was made anymore but SS or Atlas Heavy twins and the Commando. Except for the Commando production racer and Combat, Norton was done fooling with new cam grinds.

Most of what AMC did to the Norton line after 1962 was to cut costs and maximize corporate profits, which did not work they went bankrupt in a few years anyway.

Sal DeFeo's Ghost Motorcycle did not have the brains to make a stock looking Norton run faster. I used to own a hot-rodded 650ss that was built by them back in the day which had the worst head porting job anyone could think of done to it, and this is what it's original owner had to say about it: "It liked racing megs best and I never did find a �quiet� system that worked anywhere near as well. The down side was that while I was used to it, few others could ride it in traffic without either stalling or overheating the clutch." A grade-A POS.

texasSlick said:

By the way, those high comp pistons increased the vibes as well as the push....with the Atlas idling on the center stand, it would "walk" itself along...but backwards!

Click to expand...

too true, too true :!:
It saved Norton fitting into the gearbox a reverse gear :!: :shock:

My old Enfield will walk itself backward on its stand.
And it has neither twin cylinders nor high compression. !
Nor twin carbs to synch...

More-so if its warming up on a fast idle though.

acotrel said:

About the bike being 'too smooth'. I've always had the impression that single cylinder four strokes give more drive on dirt than either four stroke or two stroke twins . And Vincent engines are better in speedway sidecars than four cylinder Japanese engines. On dirt it is always a balance between slide and drive ?

Click to expand...

Kenny Roberts, on a 4 cylinder 2 stroke TZ700 (or was it a TZ750 ?) proved that this wasn't necessarily so - by winning one of the AMA half mile dirt races, was it ?
He just cruised along with the pack, and on the final lap, opened the taps and blitzed the whole field.

Afterwards, 4 cylinders were banned, as they wanted that myth of traction preserved.
And Kenny was also quoted as quipping "they don't pay me enough to ride that thing".

So maybe a more suitable word is they (single cyl 4 strokes) are 'easier' to ride on dirt ?

Although we digress, as usual...