Building an Atlas Motor from parts

The rust will give a good finish for oil retention so provided the pits aren't deep a good clean with emery should make it very useable.

I remember reading that new cylinder barrels (possibly not Norton) were kept outside for months to relieve stresses and ended up quite rusty.

Previously ian_soady wrote:

The rust will give a good finish for oil retention so provided the pits aren't deep a good clean with emery should make it very useable.

I remember reading that new cylinder barrels (possibly not Norton) were kept outside for months to relieve stresses and ended up quite rusty.

I would say finding Std pistons more of a dilemma if you don't have any? Quite right about the castings kept outside for years in some cases , but they were in an unfinished state; machined up on requirement. Honing should do the trick to remove surface rust and if with pre existing wear, it takes you out of tolerance go up a step. It depends on intended use and budget....

Cheers

Jon

Previously robert_tuck wrote:

I decided I wanted to build a 750 motor for my 99 which is getting old in the tooth. Looking at my spare rusty barrel two things strike me, Its still on std bore and measures unworn but with light rust ,any point in fitting std pistons?. The outer head bolt threads appear to be 5/16" at most , so needing a head to match? or re drilling and tapping to suit a later head? . Any other things to catch the unwary in my search for parts?..

You should be aware that the 99 is small bolt pattern head AND small bolt pattern barrels(cases). If you intend to build a featherbed 750, then the whole 99 lump goes on the shelf as almost nothing is useable for a 750.

You will need a complete atlas core i.e. larger bolt pattern barrels/cases. medium bolt pattern head, which for a featherbed atlas is 5/16 head bolts.

Phil Hannam and I have conversed that some late atlas came with 3/8 head bolts, but to date, I have never come across an example of that. Only in late 750 hybrids so far...

Heads are all here:

http://atlanticgreen.com/nhth.htm

Unsure if there is a go too for all 'Heavy' cylinder configurations?

Good luck!

Rgds,

Steve

Previously robert_tuck wrote:

After a clean of the rust and dried grease from the spare 750 barrels I have found a couple of divots and tram lines in the drive side bore so it will have to be bored. I was hoping to build a lazy easy to start low comp motor but I dont think that is possible with the current piston supply unless I can find some SH dished + 20 pistons and bore to suit.I am a bit surprised at the small 5/16 bolt sizes by the plugs, Don't recollect that our 67 Atlas was that small.I should be able to use the ignition,timing gear,cam,followers, pump and carb from the 99 but will have to get a set of siamese pipes made up as the head has a wider splay.I would have used the 99 head too but don't want to alter a good std component that I might want to use in the future when those new barrels and rods appear!!!!.I have a new unused Hemmings double S Dommy cam in the junk pile but don't think it would be of benefit so that will be for sale or swop.There is an article on the range of heads,barrels around but can't find it.

Hello Now what wrong with minus ten BHB the original sizes only go to 30 thou for obviousreasons and you can get differentsizes of honing stone that make a better job but you neededto bolt down the barrel of a good solid bench to do this job and take your time with it and lubricantas you go, and push in and out slowly, yours anna j

My 99 had flat followers, the same as the Atlas. The Altas lump has a high pressure lubrication system - 6 start pump and high pressure feed to the rockers which have plain rather than scrolled shafts. The breather and oil tank are different too. I couldn't get dished pistons for my Atlas engine at rebore time so had to go for the lowest comp Commando ones instead. It's a heavy beast to start if it has wet sumped (as they all do, given time) but it only ever needs one or two kicks so no big deal. I'm very pleased with the Atlas engine in my 99. It has a single carb and goes well.

Presumably curved cam followers will make the valves open and close more quickly?

Previously robert_tuck wrote:

I think the curved followers were designed to work with the early dommy cam (before the Daytona profile and ramps was introduced) ,I would think they may provide more lift but mess up the intended timing if used instead of the flat base ones.Not relevant to my project as I'm not in the slightest interested in any performance increase, I want this bike to be a complete contrast to my other bikes,which are all a bit mad .

Hello Well let me now tell you all this, the Flat cam follower were first fitted To the Norton Manxman 650 export only has was the high lift sports camshaft, the parts made from new on these motors whereas listed Barrels set, Crankcases, Downdraft cylinder head new type push rods the fat type which are longer for the new Flat type Cam followers and New type crankshaft with the 1:75 large end journals So the Norton Manxman motor was an all-new redesign Motor for the export market from November 7th, 1960 First machnie now unearthed frame and engine numbers 93601-18 shop number 7, second machine 93602-18 shop number - 1, Now as for Atlas Fist machine Built on April 20th 1962 with its motor has new Crankcases and New Barrel sets and New Cylinder head, Built for Export market Numbers start at 101xxx, Shop number -1 if any one needs to know more then write it on this thread Yours Anna J

Hello As for Altas pistons the originals were made by BHB Compression ratio 7:5:1 these where concaved piston tops I have a Set Still in their box with ring sets, I am rebuilding an early Atlas Motor for a Freind this motor will go into an export only Scrambler has built from 1963, Yes a Scrambler Not a Desert sled, IE N15 or P11, So low compression pistons well do well for low down torque, for the atlas scrambler , yours Anna J

Previously robert_tuck wrote:

Hi Anna,My 1959 built 99 came with flat followers as did many other 88 and 99 bikes so I don't think the later 650 had them first. Not that it its really that important .

Hello well your model 99 is a 59-year-old motorcycle and how many times has it been to strip down before you got this machine and parts changed, all my parts manuals from Bracebridge street witch give all part numbers for said years and I can tell you the Norton 650 Manxman was the first to have flat type cam followers along with improvedand updated valve train as part of the new design back then in November 7th, 1960 on even the models 88ss and model 99ss had parts taken from the Norton Manxman models to improve the valve train and Model 99ss were waring the Manxman crankcases I do have all the parts manuels including the one for the Norton Manxman in A4 36 pages, for this machnie only, with all export parts listed it was sent to me by a friend in the USA, some time ago, and I have all the Norton Twins parts manuels from 1953 on to 1962, untill bracebridge street closed in october 1962 the last manuel I got was for 1962 and with parts for Atlas export machnies very rare manuel and I have Norton brochures from 1953 to 1962 and export ones too and all the Norton manxman addvertising flyersyour and 1962/3 norton atlas ones too and a collection of Amal Catalogues and Lucas And Hepolite and B-H-B pistons catalogues I have all the Norton Books and some you cannot get anymore along with some 4,000 magazines all classic motorcycle and CBG yours Anna J Dixon

Attachment doesn't seem to want to open!

It opened right up for me.

Mike

Robert.. back on Feb 19 you mentioned you'd need to have siamezed pipes made up. My 88SS head has the same wide angle as the Atlas and Armours sold me mine some 10 years ago. So they shoukd be listed. Hopefully.

Regards David

Previously robert_tuck wrote:

Anna you are spouting rubbish again. Just as you know stuff about the Manxman ,I know stuff about my bikes. Have some respect.

Hello Now to add to your comments can you tell me how I am spouting rubbish when all this information has come from the Bracebridge street manuals and I just happen to have everything On Every TWIN made by Norton and even the Experimental twins and Single and inline four, Drawings and dimension and just happen to own Norton twins and a single or two for well over 47 years since I was 17years old, this a case of pan calling kettlegrimyarse! as we say in Yorkshire, you have to earn respect it's not given. So do not try to shoot the messenger The Facts are the facts I cannot change them just because of your motorcycle happens to be fitted with the 650 camshafts and followers from some earlier time in its lifespan, yours Anna J

To no-one in particular. For information only. (Been there, done that)â?

The standard atlas crankcases won't work with a scrambler!

The primary side is machined the same as commando and takes the matchless type primary cases. Tin cases will not fit.

The early cases only had small oil passages too that are OK for 3 start pump gears but will need to be opened up for 6 start gears. The 3 start was used with the early rods with no bleed hole and changed to the bleed hole (stronger) rods with the introduction of the 6 start gears.

Hope this helps

Paul

Previously paul_nicholls wrote:

To no-one in particular. For information only. (Been there, done that)â?

The standard atlas crankcases won't work with a scrambler!

The primary side is machined the same as commando and takes the matchless type primary cases. Tin cases will not fit.

The early cases only had small oil passages too that are OK for 3 start pump gears but will need to be opened up for 6 start gears. The 3 start was used with the early rods with no bleed hole and changed to the bleed hole (stronger) rods with the introduction of the 6 start gears.

Hope this helps

Paul

Hiyah Paul and no-one in particular - The stronger rods, with a blunt 'V' at the big-end eye, were introduced initially at engine number 111920 without the bleed hole. However, yes you are correct that the stronger rod with the bleed hole was accompanied by the six-start oil pump gearing. In fact this mod with the larger oil-ways and pressurised rocker feed and all that went with it was only introduced at engine number 116372. Many Atlas's did not get the double speed pump nor the larger oil-ways so are they really necessary on a torquey plodder ? Probably not.....Oh hum ! Cheers, Howard

Previously robert_tuck wrote:

I too have parts books from that time and they show the 88/99 models made in late 59 having the same part number for the followers as the later 650. I also have a 59 made 99 which is fitted with these parts as was my 60 built 88 . Read the books.

hello yes part number 21225 QR camshaft for models 88/99 from September 1958 to late1961,

now for the 650 Manxmanhigh lift camshaft, part number 22729 also fitted to the 650 de-lux and 650 standards, and after April1961 the model 88ss and model 99ss so try reading your parts manualright, and I can give you everypart number there is for Nortontwins and some you never see, has there in the Manxman parts catalogue only for export, and only fitted these machines, not even the 650ss or the atlas received some of these specialparts, and not made now, yours anna j