Help building a bitsa

Jon, your frame is a wideline and the Atlas is a slimline.and you can see that from the side anyway. But only someone looking at the frame and engine numbers would know that it wasn't a 58/59 Dommie 99 at first glance, If that's the style you are after.

The single front mounting point of the wideline isn't an issue. The second front mounting point was standard on all slimlinetwins from 1960. But, I do believe that the frame was strengthened around the headstocka little after the 650 was introduced. Anyone care to comment on that.

There is another thread where someone was concerned about the single engine mounting point of the wideline frame.

Jon, there is but take my advice and take the motor down and examine all parts and take photos. You could also consider a bigger engine sprocket, say 23 or 24 teeth to keep the revs down and maybe reduce vibration.

I bought my 650 motor as rebuilt, I didn't check the bottom end, it turned over well and there was not even a ridge at the top of the stroke. But it looks like the big end is suspect and will have to come apart. Bugger after all other issues are sorted.

Still waiting to hear from anyone advising on frame strengthening or perhaps it was a weak spotfound only on slimlines?

I have a 1956 99 rolling chassis, almost complete. The engine I have found is out of an Atlas. My question is, should I modify the front engine mounts on the frame to look more like the Atlas frame? It would be a shame to keep the 99 original only to find out there was a good reason why they changed the frame for the Atlas.

jon soons

Well If your thinking of fitting a Atlas Engine In a wideline Frame You Need to have four mounting lugs at the front as the Atlas had a nice time of ripping some of it mounting lugs of or Cracking the weld and I would make thicker engine plates for the left hand side as this is where all the power comes from and I found that the Atlas motor can bend the rear Engine plate and it also likes to try pull the clutch off too , as for engine sprockets you can only get a 22 tooth engine sprocket on as any bigger than that, your chain is then craving up your alternator mounting, and I would also put a double top engine mounts on the cylinder head one for the front end and one for the back end you have to make the back one up but its help to keep and powerful engine in its place , and owns have found that the Atlas Motor can vibrate your Nuts and Bolts lose over time these atlas motors are power beasts and much like the 650 motor but with more bottom end torque than the 650 has but the overhaul out put BHP there about the same at 49/50 Bhp @6250 anyway all the best with it your anna j

3/8 holes mean a later Atlas barrel, a Comando barrel or an early pre 1966 Atlas barrel that has been re-threaded.

If the head has 5/16 bolt holes then it must be a pre 1966 item for a spigotted barrel. However, you can fit this head on the later barrels by firstly getting the bolt holes enlarged. Only the 4 by the spark plugs need to be done. Then get hold of a pair ofsteel ring inserts (part number 25494) to fit inside the spigot recesses, allowing it to be used on unspigotted, flat topped barrels.Aluminium versions of this ring were also available at one time.

I fitted an Atlas engine to my early slimline frame (1959) about 15 years ago. None ofAnna's horror stories have happened to me - and bear in mind I don't tootle about at 50mph. I don't know how much personal experience she has of Atlas engines over the long term to justify her comments. The engine is smooth and torquey and quick. The vibration is perfectly acceptable - no worse than many a 99 and funnily enough a Commando owner who took it for a ride recently said it vibrated rather less than his bike.Your fingers still work after a600 mile day. I run the standard 21 tooth engine sprocket. The only change compared with the 99 was to add an extra clutch plate and associated longer clutch pushrod to stop a tendency to slip. Fitting the Atlas engine was the best thing I ever did to my bike.

I have a friend that has an Atlas engine in a wideline 99 frame, it's been there since the eighties, it's nicely tuned, he rides the nuts off it & puts in some high mileage. He too had a bit of trouble stopping clutch slip so has converted to Commando clutch but I've never heard him have any of the problems that Anna has mentioned, it does vibrate a little, but things don't come undone & fall off. I would say it's only marginally worse than my own standard 99.

Regards, Tim

Previously tim_gostling wrote:

I have a friend that has an Atlas engine in a wideline 99 frame, it's been there since the eighties, it's nicely tuned, he rides the nuts off it & puts in some high mileage. He too had a bit of trouble stopping clutch slip so has converted to Commando clutch but I've never heard him have any of the problems that Anna has mentioned, it does vibrate a little, but things don't come undone & fall off. I would say it's only marginally worse than my own standard 99.

Regards, Tim

My bog-standard dynamo 99 vibrates like hell and always has. Any suggestions to reduce that would be welcome! Tom McEwen

Thanks Anna j. You realise this means welding. I was doing some trial fitting on the bench and realised not only my pistons are Commando but so are my barrels. The head has 5/16 bolt holes and the barrel has 3/8. This puts a serious crimp in the plan. I read in the technical articles that the boltholes cannot be enlarged on the spigot heads but what about the non-spigot like mine?

Hello Well I am a real good welder that can weld holes up even fresh air can be welded , but rust I not perfected welding this yet and Making thicker engine plates is not a bad idea as these Atlas Motors are real Beasts when there running now as for Nuts and Bolts and stud bar You cannot beat Nookys Nuts on ebay .co.uk he supply's Nuts and bolts and threaded stud-bar and domed nuts for BSA Triumph and Nortons or any other British made motorcycle and his producs are the nicest finish I have ever seen on the humble nut and bolts you should give him a try out , and a double head steady is a other not so bad a idea until you need you cylinder head off , but the best way to do this is to take the hole engine out is a lot easier to fit a cylinder head as then you have the engine on a engine stand so you can then work on it with ease happy spannering Yours Anna J

I fitted an Atlas engine to my early slimline frame (1959) about 15 years ago. None ofAnna's horror stories have happened to me - and bear in mind I don't tootle about at 50mph. I don't know how much personal experience she has of Atlas engines over the long term to justify her comments. The engine is smooth and torquey and quick. The vibration is perfectly acceptable - no worse than many a 99 and funnily enough a Commando owner who took it for a ride recently said it vibrated rather less than his bike.Your fingers still work after a600 mile day. I run the standard 21 tooth engine sprocket. The only change compared with the 99 was to add an extra clutch plate and associated longer clutch pushrod to stop a tendency to slip. Fitting the Atlas engine was the best thing I ever did to my bike.

John, these are US owners Horror story's On Norton Access.com chat site you should go and read them some are even really funny so have fun yours Anna J

John? Who he? At least my Atlas experiences are first hand.It's a pity the engine is so maligned. If it wereso bad, it would never have been continued as the basis for theCommandos. Most people agree that the 650 engine is the one to have - but the Atlas engine isessentially a big bore 650. How anextra 5 millimetres on the bore can turn an excellent engine into a frame-breaking beast puzzles me.

Well, not exactly, Gordon, in that the factory felt the only way they could carry on with the 750 was to rubber mount it, and that was cheaper than designing a new engine, with balancer shafts, or whatever else would have been required.

Us riders of parallel twins tend to accept a certain level of vibration as normal, so a bit more isn't too bad; really; is it....? History tells us that the Atlas tipped the scales beyond acceptability, given what was starting to come in from the Orient.

I have owned my 650SS-engined Wideline for 7 years now, am riding it from Cornwall to the Isle of Man and back in a month's time, but I do wish it vibrated less!

Cheers. Ian