1967 Atlas Gearbox Mainshaft Circlip and Gear Bushes

[jms]

Hi Folks.
Had a horrible sound coming from the gearbox when kick starting. Tore it all down to find the problem and actually found that the problem was I didn't realize that a circlip attaches to the mainshaft just behind the clutch basket. I did find that some of the gear bushes needed attention so probably was good thing that I pulled the gearbox apart. Oddly I don't see the circlip listed on any parts (Andover Norton) gearbox breakdown. I have read that there was part # 06-8052 which has been superseded by #06-8072. Does anybody know if #06-8072 works on an Atlas mainshaft or what the difference is between the two parts? I am going to take the opportunity to re-bush the gears and recognize that layshaft 2nd gear and mainshaft 3rd gear are a slide fit in the gears. My mainshaft 3rd gear bush doesn't slide so at some point something went wrong. For all of the bushes what is the shaft to bush clearance that I should be looking for? Most of them measure .003 -.004 clearance. Thanks

 

[Schwany]

Commando mainshaft has the circlip for certain. I am not 100% sure, but I don't think pre-Commando AMC mainshafts for 3 spring clutches had the circlip. My '67 P11 AMC gearbox mainshaft does not use a circlip. The clutch basket or hub butts up against a shoulder on the mainshaft. Somebody may have put a Commando mainshaft your gearbox, because they do fit, but are shorter or longer on the drive side. I can't remember which off the top of my head.

And most importantly I could be wrong and need a respectable fact checker to straighten it all out.

 

[jms]

Commando mainshaft has the circlip for certain. I am not 100% sure, but I don't think pre-Commando AMC mainshafts had the circlip. My '67 P11 AMC gearbox mainshaft does not use a circlip. The clutch hub butts up against a shoulder on the mainshaft. Somebody may have put a Commando mainshaft your gearbox, because they do fit, but are shorter or longer on the drive side. I can't remember which off the top of my head.

And most importantly I could be wrong and need a respectable fact checker to straighten it all out.

Thanks Schwany
Just heard from Andover. My mainshaft is NOS for Atlas and does NOT use a circlip. I’m using the RGM belt drive and will simply drop a shim in before tightening up the clutch. Roger at RGM probably addressed this in his belt drive install narative but I appatently missed it. Duhh. I’m slowly, very slowly becoming an expert

 

[Schwany]

Thanks Schwany
Just heard from Andover. My mainshaft is NOS for Atlas and does NOT use a circlip. I’m using the RGM belt drive and will simply drop a shim in before tightening up the clutch. Roger at RGM probably addressed this in his belt drive install narative but I appatently missed it. Duhh. I’m slowly, very slowly becoming an expert

Do not listen to me if being an expert is important. Getting things done is more important to me. Shade tree engineering BS follows:

Hmmm, making a shim that will work where you are thinking about dropping it in is easier said than done. You'll see when you get to it. I've got a RGM clutch for a pre-Commando mainshaft that just happens to be in a TTi gearbox. No bueno on the shim idea for me. I felt like I was losing too many threads on the end of the mainshaft trying to come up with a shim. I had the same problems with an AMC gearbox with the pre-Commando mainshaft.

You might be better off making up a long 3/8-20 stud from threaded rod you can slide a spacer onto between the frame and back of the inner primary that takes the place of the stock center mount for the primary and force the inner primary cover toward the gearbox 3/32" or whatever minimum spacing will provide clearance. Yeah I know that's barn yard engineering, but it can work. Just don't tell anybody that is confident they know everything about Norton motorcycles that is what you did.

Somebody must have gotten an RGM clutch in a 650SS and know of a better way to get it done.

What I did with the stock P11 primary to get a RGM clutch in it was sacrilegious.

 

[jms]

Do not listen to me if being an expert is important. Getting things done is more important to me. Shade tree engineering BS follows:

Hmmm, making a shim that will work where you are thinking about dropping it in is easier said than done. You'll see when you get to it. I've got a RGM clutch for a pre-Commando mainshaft that just happens to be in a TTi gearbox. No bueno on the shim idea for me. I felt like I was losing too many threads on the end of the mainshaft trying to come up with a shim. I had the same problems with an AMC gearbox with the pre-Commando mainshaft.

You might be better off making up a long 3/8-20 stud from threaded rod you can slide a spacer onto between the frame and back of the inner primary that takes the place of the stock center mount for the primary and force the inner primary cover toward the gearbox 3/32" or whatever minimum spacing will provide clearance. Yeah I know that's barn yard engineering, but it can work. Just don't tell anybody that is confident they know everything about Norton motorcycles that is what you did.

Somebody must have gotten an RGM clutch in a 650SS and know of a better way to get it done.

What I did with the stock P11 primary to get a RGM clutch in it was sacrilegious.

Hmmm. I assume you’re referring to the fact that the mainshaft threads diameter is greater than where the shim would sit behind the threads on the shaft?

 

[Schwany]

Hmmm. I assume you’re referring to the fact that the mainshaft threads diameter is greater than where the shim would sit behind the threads on the shaft?

Maybe. I'd have to look at the hub and mainshaft again. A drawing would be worth more than 1000 words of my babble.

 

[norton bob]

have to be carefull to avoid having the clutch/spider load up the sleeve gear once the clutch is fully home ,any shim needs axial clearance there otherwise you will mess up gear changing /neutral selection ,

 

[jms]

Maybe. I'd have to look at the hub and mainshaft again. A drawing would be worth more than 1000 words of my babble.

Just came in from the shop. Couldn't stand the suspense. I see the concern. Once shimmed the remaining threads to grab hold of the clutch center. In my case my shaft has a total of 9/16" of thread and adding a .110 shim leaves me with 7/16" of thread. Not terrible. Now need to look at what Norton Bob is saying

 

[jms]

have to be carefull to avoid having the clutch/spider load up the sleeve gear once the clutch is fully home ,any shim needs axial clearance there otherwise you will mess up gear changing /neutral selection ,

Bob
Are you saying that with the clutch center fully fastened up to 50 PSI, that the mainshaft length affords the sleeve gear a wee bit of clearance and shimming deletes that clearance therefore the only real solution is to alter the inner chain case?

 

[Schwany]

Just came in from the shop. Couldn't stand the suspense. I see the concern. Once shimmed the remaining threads to grab hold of the clutch center. In my case my shaft has a total of 9/16" of thread and adding a .110 shim leaves me with 7/16" of thread. Not terrible. Now need to look at what Norton Bob is saying

So does the .110 shim give you full clearance with everything tightened up, outer cover on, and the clutch spinning with the engine running? Should also take it for a ride if weather permits to check what happens when the clutch fully warms up. 10 miles with some stop and go should heat it up.

I'm not sure how much the clutch basket grows from heat front to back, but heat does make the basket diameter increase resulting in a tighter belt.

 

[jms]

So does the .110 shim give you full clearance with everything tightened up, outer cover on, and the clutch spinning with the engine running? Should also take it for a ride if weather permits to check what happens when the clutch fully warms up. 10 miles with some stop and go should heat it up.

I'm not sure how much the clutch basket grows from heat front to back, but heat does make the basket diameter increase resulting in a tighter belt.

 

[jms]

lt does provide the clearances needed and it could be less than the .110 , that’s just what I had. I tried .030 but that wasn’t enough. If I understand what Norton Bob is saying any shimming that bears on the sleeve gear collar will have an ill affect on the operation of the gearbox thus making shimming a bad idea. I was unaware that the sleeve gear collar couldn’t touch the back of the clutch basket. In Rogers at RGM’s belt drive install instructions, which I revisted yesterday, he notes that its close and that alteration of the inner cover may be nessesary. shimming isn’t mentioned. Now I know why! So back to “ shade tree engineering” as you call it!

 

[jms]

excuse me. “ Barn Yard Engineering “

 

[jms]

Well I guess my only option is to alter the inner primary cover for clearance. Only looking for 1/16"- 3/32". I may be able to flatten out the raised section inside the cover or rework the support tab that ties into the lower gearbox housing bolt. The amount that I need is so minimal I don't think rear chain and sprocket interference should be an issue. I was wondering whether a Commando mainshaft with circlip would also solve my problem thus allowing me to shim off the circlip?

 

[jms]

Images of the inner primary

 

[Schwany]

The shim would have to go in front of the splines on the mainshaft, not back against the sleeve gear. It would be difficult to make a shim that fits in front of the splines with the tools I own. A hacksaw and a variety of files has it's limits. That's why I ended up with no bueno trying to get clearance with a shim. A machinist would/might be able to figure it out as long as he/she had the machinery to make the shim.

**** Unnecessary words start:
The belt drive clutch hubs are different for a pre-Commando. If you have a Commando hub you are kind of screwed without a Commando mainshaft in the gearbox.
**** Unnecessary words end.

Shorten and reweld the offset of that mounting bracket at the bottom rear of the inner primary cover to get clearance. You might have to do some small amount of shortening at the other mounting point high near the middle... maybe. Essentially you'll be pulling in and bending the inner primary a little. Not enough to kink the metal, but just enough to get some clearance.

You could cut the guts of that hump out of the inner primary too, but that's extreme.

 

[jms]

The shim would have to go in front of the splines on the mainshaft, not back against the sleeve gear. It would be difficult to make a shim that fits in front of the splines with the tools I own. A hacksaw and a variety of files has it's limits. That's why I ended up with no bueno trying to get clearance with a shim. A machinist would/might be able to figure it out as long as he/she had the machinery to make the shim.

**** Unnecessary words start:
The belt drive clutch hubs are different for a pre-Commando. If you have a Commando hub you are kind of screwed without a Commando mainshaft in the gearbox.
**** Unnecessary words end.

Shorten and reweld the offset of that mounting bracket at the bottom rear of the inner primary cover to get clearance. You might have to do some small amount of shortening at the other mounting point high near the middle... maybe. Essentially you'll be pulling in and bending the inner primary a little. Not enough to kink the metal, but just enough to get some clearance.

You could cut the guts of that hump out of the inner primary too, but that's extreme.

Yea these are my thoughts as well. cutting out the raised section solves the problem but introduces the potential for unwanted debris.

 

[norton bob]

Not having worked on a Commando much or used a belt drive at all ,I'm a bit in the dark !. But you can be sure that the clutch center must not grind against the end of the sleeve gear as they can rotate at diferent speeds . And contact does affect the slickness of gear changing ,although in theory it should not make much difference , Usually the problem manifests itself when the outboard end of the spider on Dommy clutches starts to disintigrate internally and the clutch migrates towards the box under the force of 70 ft lbs

 

[jms]

Yea these are my thoughts as well. cutting out the raised section solves the problem but introduces the potential for unwanted debris.

 

[jms]

Well success. Spent two hours or so and made a shim out of a .050 hardened washer that fits the spline of the clutch center. A lot of hand work with a Dremel and small fine file. Dropped in and now the clutch is spinning without interference. Thanks for everyones help