1966 Atlas gearbox removal?

I am helping a friend rebuild the AMC g/b on his Atlas. We have been able to, almost, strip the entire box with the exception of the layshaft, drive side, ball bearing. I also want to be able to give the shell a good cleaning and examine it for cracks.

The primary is off, the chain and g/b sprocket are off the last hurtle is being able to remove the lower g/b mounting stud, which, of course, is blocked be the frame rails. At first look it would seem that removing the 4 rear cradle fasteners, supporting the engine and raising the rear of the motorcycle via the swingarm tube would permit the lower mounting stud to be easily removed. On a second look I see the center stand and the side stand may prevent this.

Searching this forum and the internet has not shed any illumination on the quest. I would greatly appreciate advice and a procedure from any of you that have done this level of service, or a pointer to what I have missed in my searching.

Best.

According to my Norton Maintenance Manual:

"With this frame,it is not possible to remove the gearbox as a separate unit and if, therefore, it becomes necessary to remove the gearbox shell, then it is essential to lift the engine/gearbox assembly from the frame as described in para. 31."

Para. 31 describes the typical procedure to get the engine/GB assembly clear of the frame.

Slick

Thanks Slick.

The quote from the "Norton Maintenance Manual" is a bit confusing to me. I have stripped the g/b to it's shell, it is completely empty except for the drive side layshaft bearing, the primary and the final drive have been removed, does the quote mean that at this stage I need to remove the cradle with the engine and g/b shell still attached just to be able to remove the g/b bottom stud?

There appears to be plenty of room to remove the g/b shell through the cradle if I could get the bottom stud out. The center stand and the side stand look like they might be issues, but having never worked on an '66 Atlas I don't know.

Best.

RoadScholar said:

Thanks Slick.

The quote from the "Norton Maintenance Manual" is a bit confusing to me. I have stripped the g/b to it's shell, it is completely empty except for the drive side layshaft bearing, the primary and the final drive have been removed, does the quote mean that at this stage I need to remove the cradle with the engine and g/b shell still attached just to be able to remove the g/b bottom stud?

There appears to be plenty of room to remove the g/b shell through the cradle if I could get the bottom stud out. The center stand and the side stand look like they might be issues, but having never worked on an '66 Atlas I don't know.

Best.

Click to expand...

The last part of Para. 31 says:

"Remove the remaining bolts holding the engine/gearbox assembly to the frame and lift the assembly clear of the frame."

I interpret both quotes from the manual to mean it is flat out not possible to remove the GB without lifting the engine out of the frame.

Looking over my Atlas, it appears that if the engine/GB were jacked up a bit (requiring head steady removal and removal of all side plate to frame fasteners except the frontmost), the lower stud could be removed, and then the GB passed out on the left side.

Let me know if this works for you as a GB rebuild is in my future.

Slick

texasSlick said:

Let me know if this works for you as a GB rebuild is in my future.

Click to expand...

I spent a fair amount of time looking at the shell/cradle/centerstand and 'am going to try supporting the engine/frame and seeing if I can hinge the cradle enough to remove the shell. I should know sometime tomorrow and I'll post my experience.

Best.

I think but not sure that if you just leave the top two bolts in the back of the cradle you can pivot it upwards enough. But I can't remember if that is with the head off, and of course this is without any of the other parts mounted to the cradle. So it may only be good for reassembly. All that said it may just be easier to remove the whole thing. lol. I'm going to be putting mine back together soon also.

I didn't have the time yesterday to work on the Atlas, but with the bike on a lift and the front strapped securely I'm pretty sure that supporting the engine, removing the centerstand, removing the 4 rear most cradle fasteners and 2 of the 3 cradle to engine, possibly all 3 fasteners will allow the cradle to hinge up or down enough to withdraw the g/b shell or the cradle w/g/b.

I will follow up as soon as get this done.

With the full primary drive off the magneto looks a lot easier to service/time. Do either of you know if the '66 Atlas's mag has a mechanical advance?

Best.

As far as I know, they all had an AAU until they did away with magnetos.

Slick

Sorry for the delay in following up, but we did get the g/b case out without removing the engine, and all that that process entails. Prior to the procedure below we started with removal of the complete primary drive and left side header/silencer, as pictured above.

This what we did:

1) remove side stand and center stand
2) remove trans adjuster bolt
3) removed the 4, 1/4" fasteners that support the bottom of the oil tank and tool box
4) supported the engine
5) loosened the lower cradle to engine bolt
6) removed the 2 upper engine to cradle studs and the 4 rear cradle to frame fasteners.

The cradle plates pivot down nicely allowing the removal of the lower g/b through stud. The g/b then comes right out. The right side header/silencer will be removed prior to reinstalling the fully assembled g/b.

We will also have at the magneto as it won't be any easier to get at. We will remove the timing cover to replace the crankshaft oil seal, the pump to cover seal and to re tension the cam and mag chains, being prepared to replace both if needs be. This Atlas will getting a belt drive primary along with a new engine seal.

Best.

texasSlick said:

According to my Norton Maintenance Manual:

"With this frame,it is not possible to remove the gearbox as a separate unit and if, therefore, it becomes necessary to remove the gearbox shell, then it is essential to lift the engine/gearbox assembly from the frame as described in para. 31."

Para. 31 describes the typical procedure to get the engine/GB assembly clear of the frame.

Slick

Click to expand...

I have found it on YT Might be it can help to know about the removal of the gearbox.

I was waiting to see the side-stand lug. I see that, like mine, it has been broken and welded. When I had the engine out of mine I corrected this "fault" and put the proper lug on. Should have left well enough alone. The lug I so carefully prepped the frame tube for is now broken again. But the original tin primary does not leak (this week anyway) so I'm loathe to take it apart to fix the stand lug.