Gearbox Assessment - What Did I Discover?

It was a nice day to get into the garage. I was able to build a work table and then jump right into tearing the gearbox down. It should be no surprise that I found a few hidden issues that will need to be addressed.

Thanks to Swooshdave for posting the photos of his teardown...it was very helpful!

http://www.accessnorton.com/gearbox-teardown-with-plenty-pictures-t5434.html



When I purchased the bike, the outer cover was off, so I suspected some issues.



I had to improvise a hold down to get at removing the main shaft nut. It came off pretty easily.



I started to split the inner case, expecting a rush of gear oil. None to be found, probably not a good sign.



Metal chunks laying inside is probably another bad sign. No reason to turn back now.



More damage.



Backside of the inner cover. Should I replace this part?



1st Gear Lay. Looks pretty rounded off, I am going to assume that this needs replacement.



Hard to see in this photo, but the lay shaft bearing came out with the shaft. No heat required. Looks like it has been spinning in the case.



I was able to push the main shaft bearing out by hand. Slight signs of spinning in the case. Both bearings are rough and notchy.



Some corrosion on the main shaft gears. Do these need to be replaced?

I looked for cracks in the case to explain the spinning bearing, but did not see any.

So what is the verdict? What parts to I need to replace. Any other tips to look for while I have it apart?

I would probably glass bead the gears and use them. They may not last as long as new ones but you will likely get several years out of them. Look close at the case at the thin section between the bearing bores. They often crack there. If the bores are just a little loose and not hammered out till the bearing can move around I would clean it up good and slide the new bearings in with a light coating of JB weld in the bores. It does a much better job of retaining a bearing than Locktite. Jim

I'll start with the easy one - that kickstart pawl has GOT to go.

Yeah, I'd be looking to replace that first gear lay.

Can't quite tell what's corrosion and what's just...sludge on those main gears - can you post pics of them cleaned up somewhat?

Some bearing retainer on the new layshaft bearing may do the trick...?

PS edit, now having seen Jim's reply. Jim, I generally defer to your far greater wisdom in these things but the thought of JB Weld in there gives me pause...what happens if you need to replace that bearing (race)???

Yes, The kicker pawl and first gear and the kicker shaft that is cracked under the pawl will need to go. But the inner case will probably survive. Jim

PS edit, now having seen Jim's reply. Jim, I generally defer to your far greater wisdom in these things but the thought of JB Weld in there gives me pause...what happens if you need to replace that bearing (race)???

Just heat it like you would a tight case and the JB weld will soften and release.

Ha! Never knew that about JB Weld. How the heck does that stuff hold up in hot (e.g., engine, exhaust) applications?

Good eyes. I had to go back to spot that kicker shaft crack.

Thanks Jim.

BrianK said:

Ha! Never knew that about JB Weld. How the heck does that stuff hold up in hot (e.g., engine, exhaust) applications?

Good eyes. I had to go back to spot that kicker shaft crack.

Thanks Jim.

Click to expand...

Brian,
In the exhaust port, not very long. In the intake port it lasts pretty good if it has something to hang on to. I have used it on crankshaft bearings that were not tight enough in the case and found it held where bearing mount would not. It works pretty well to keep that outer cam bushing from turning in the case too. Jim

Very glad to know Jim C. uses JBW. Its a favorite tool of mine, even creating a new cylinder fin out of it. But it does soften over 400' F, way more than gear box will see, but for maybe a spinning outer race in the case. Its takes days for JBW to really set up hard, so would be pensive to hop on with just over night set up, even in thin layer. I'm thinking more to order the low melt alloys, one that melts about 350'F to pour into textured bore and outter race. I've a Quaife gear box to recover its hold on bearings. If worse came to worse, could just have a stick welder attach a stick to the inner race, then wait till stick cools and heat flows to case then just lift out like an hors d' ouerve on a tooth pick.

Who knows how tight the primary chain got before your time, only takes once to make shafts bend like a candy cane twist, check em and know.
BTW the bush kits all require a reaming to fit, ask how to do that or have it done. Sand paper is frowned on d/t imbeded grit.

Thanks for the advice and recommendations. I will take some measurements of the bearing recess dimensions in the case to see where I stand with respect to the outer bearing dimension.

Good advice on the shaft straightness, I will take a look at it on a surface plate. My fingers are crossed that they are not bent.

The JB Weld is a new one for me. Is it best to apply a small skim to the bearing race and then insert to set?

So far my tally of parts includes:
Bearings
Gaskets
Bush Kit
1st Gear Lay
Kickstart Shaft
Kickstart Pawl
Inner Cover (Optional per Jim, probably will replace while I am at this)
Misc Springs
Outer Cover Fasteners (None came with the bike)

Does anybody have experience with the RGM gearbox rebuild kit? This may be where I start for completeness of parts and then add as needed to the order.

Thanks for sharing your knowledge. More to come.

comnoz said:

It does a much better job of retaining a bearing than Locktite. Jim

Click to expand...

It's good to know you have had success with JB weld. It is easy to source, readably available and affordable.

I recently needed to replace bearings in bicycle frames and the manufactures recommendation was to use Loctite 680 to secure the new bearings. Previously, I was only familiar with the standard red, blue and green formulas found in auto and hardware stores. It was an eye opener to find that Loctite and Permatex both offer a larger line of retaining options. The 680 was harder to source, and redicuslvy expensive, ( .34oz bottle was about twenty bucks) but it did the job and I have plenty to spare.

I am curious if you think the 680 would work in this or other Norton bearing retention applications.
Loctite retention: http://www.henkelna.com/industrial/prod ... Dsearch%7C

Loctite 680: http://www.kraftindustrialsupply.com/My ... 680-EN.pdf

I don't remember the part number of the locktite brand I have used. I do recall it was called stud and bearing mount and is rather expensive. It seems to work pretty well if the bearings are a very close fit however I have found it does not work very well to keep crank bearings from turning in the engine case where I have had success with JB weld. Jim

30 years ago, I ported a Yamaha SR500 head with JB Weld.

Drilled and tapped holes from the bottom side/head gasket side of the port. Screwed machine screws into the new tapped holes such that the screws stuck up into the port. Laid multiple layers of JB Weld into the port floor. Raised the port floor maybe 3/8th inch. The JB Weld gained plenty of grip and structural strength from those machine screws. Die grinder cut off the tops of the screws that were proud of the new port floor. JB Weld in the floor of the cam/valve spring box allowed the port to be lifted up into the cam/spring box. A "tent" made from a strip of aluminum sheet, embedded in the cam/valve spring box JB Weld helps ensure that the JB Weld doesn't fall into the port.

That head is still sound, no JB Weld has lifted, cracked, or separated.

I ported a Norton head several years back and had a single # 10 screw through the intake port floor with jb weld about 3/8s deep around it.
During practice a few months later I got a bad engine noise. When I pulled it apart I found the JB weld had split at the screw and a large chunk had gone through the motor. I have ported several motors since with JB weld with multiple screws and had no problems except for slight lifting at the edges.
But no lasting results on the exhaust side. Jim

Dear sirs, a couple decades of attempts with the best Locktite offers by the best machinists builders there is has failed 100 percent of the time to hold ANY engine or gear box bearing race stable at ALL> Period - End of story- Throw in the ole towel on Locktite - except for way cooler and lesser vibration loaded applications, such as bicycles or about anything but where its most often mentioned and fails in Brit Iron engines and gear boxes. Epoxy or solder, or weld or peg or stake or build up plate and remachine, but foregetaboutit here with Locktite bearing goop.

You have been warned and my only alert - so go ahead and try to prove it wrong, again and again and again and again and again and again and again ditto ditto.
I want to hear real solutions for my own needs, not waste time on proven failure.

JBW is not very good at chemical bonding type adhesion, its only good for pure mechanical fill in and connecting, it must have something to physically grip and prevent it bending or it cracks and lets go, plus gets soft near its heat threshold.
Fine if just soft but sitll held intact in place by studs, dimples or wire- compostite fibers. Its black part is steel dust filled and magnetic attracted to help retain it in pores and gaps and against gravity till set up.

There are literally piles and piles of thousands of AMC gear boxes at various vendors around the world with only thing wrong being the wallowed out bores.
I know because I called all around the world to speak at length with many an ancient vendor - cause Ms Peel got sloppy and I blew its back side out trying to get a bearing to stay in bone cold. All wanted about new prices for pieces of crap - till I found out Altas AMC gear box works even better than Commando at half the price. Only difference is lack of the notch that needs the dang ole thick washer to bash about for removal and install, a breeze with the Altas version.

Clutchout,
looks like your on your way to repairing the gear box. By the way nice photos of the traney, and please keep those photos coming! Ah, that didn't sound quite right!

Hope you found the discussion on JB Weld helpful. Sorry but that was an unintentional bit of hijacking. I love epoxies and use them to repair all sorts of projects, mostly favorable but I have had mixed results.

The JB Weld packaging is loaded with all sorts of claimed uses. I am amazed to hear of successful JB Weld motor repairs being performed by the Norton tribe. Good to know it works retaining bearings. Thanks boys for the info!

T95 said:

Hope you found the discussion on JB Weld helpful. Sorry but that was an unintentional bit of hijacking.

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No issues from me on where the discussion went. That is why we are all here; some to ask and some to answer questions. I rather enjoyed the discussion and the enthusiasm for the many uses of JB Weld. I have to admit that I have some in a drawer, but have never found the need to use it. I guess I have not opened my mind to all of the hidden potential the product has to offer.

I have been doing some online shopping of parts from the various online vendors. I want to make sure I get it right to avoid an extra shipping fee.

I have used RGM rebuild kit of bearings and bushes but forget what else it might had.
I do remember about all the bushes were a bugger to ream by hand at home w/o any reaming tools, many hours of working them onto shafts, no sanding. Next time off to machinist. Live a learn on a Commando the hard way for me.

You need to save one of the old sleeve gear worn bushes to put between the two new ones as a spacer to keep the new bushes apart and help em hold the bowing shaft more stable. This area hardly gets any lube so also good idea to spiral groove them but stop short of the outer edge of DS bush or may leak more oil into clutch.

Gear box does not need any gaskets, just a factory time saver to close up. They do
nothing by space bearings/components further apart and tend to crush down, sometimes allowing the TS main shaft nut to come off. Your call but I gave em up
a few trans rebuilds ago. I use Permatex Hi Temp Racer Blue Hylomar for Every
sealing need on Nortons - head to kick shaft sealing.

Kick shaft sealing is an issue, factory oil ring is a loose fit. A piece of foil in the case groove then packed with RTV or Hylomar, slip in light greased shaft and let
set up with oil ring, seals about as well as the machined cases for Honda type oil seal.

Kick lever holding on is an issue. Saw the slit half again wider for more splines to bite and maybe longer bolt with a nut to back it up.

Keep close observation of which way each cog faces, some have a slight lip
but can go back either way, unknown till testing assembled fails.

Also pay close observation of where to index the shift cam gears putting on outer cover, its goes on just short of preventing case to close. A study in meditative control of emotions and will power in my learning curve to get that detail down.

Other crazy maker is the shift pawl clothes pin spring, Main issue is to get both legs parallel and gaped from pawl enough to let it swing past. Its a favorite place for leprechauns to mess with after you got it right on the bench, not right by time installed.

I came up with a fix for your spun bearing. With the bearing in place, mill 4 small holes, 90 degrees apart, at the perimeter, then tap and insert 4 set screws with loctite. That will prevent the bearing from ever spinning. They do this on airplanes for different things. They also stake the bearings in, but that is not possible with those bearings. Hope this helps, Brent

Regarding the mention two posts up of widening the kicker clamping slot...
No offense to anyone but I found that opening up the clearance side of the pinch hole was more of a success that messing with the slot.
As the screw is tightened the clearance and the thread are forced from being coaxial and the screw tries to bend.
I forget what size drill I used but increase it by 1/32 sounds familiar. Maybe go 1/64 at a time and try it.
A bitch to do with a hand drill, it will want to grab and bink goes the bit. Use a DP or Vert mill.
All the best.

comnoz said:

... slide the new bearings in with a light coating of JB weld in the bores. It does a much better job of retaining a bearing than Locktite. Jim

Click to expand...

Is heat applied to remove bearings that have been fitted with JB Weld?