Norton AMC gearbox 4th gear bushes

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My mainshaft roller bearing works quite well , was installed many years ago without any shims on the shaft. The thin sleeve for it was made from aluminum . Oil is clean , no metals steel or bronze. Have no numbers to give as it was installed before I started the Logbook. Now I log every change or maintenance work performed noting when and what. I believe the really important thing is to upgrade the layshaft bearing first and foremost. Never seen a mainshaft bearing fail. Have seen galling occur to the 4 th gear bushes though likely from lack of lubrication. I use Redline HD shockproof Red now. Coats everything including inside the outer cover where condensation/rust can occur. :)
 
Thank you to all who helped here.
I have new bushes in the main gear and now have replaced the layshaft ball with a new roller brg.
I have .070" end play at this time and I am concerned about the advised shim install, at the kick start, moving the kick start mechanism too far out of its latch.
So after looking this over I am asking if alternate shimming has been done?
I am thinking about shimming, all or partial, at the new roller inner race.
 

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.070 seems excessive. Both of my AMC gearboxes only needed .010-015 shimming after installing a roller layshaft bearing to end-up with around .010 end play. Are you sure you have the inner cover seated and tightened?
 
I don't have that much play and by not using the gasket between the inner cover an the main casing after making sure the joint faces were good the end float was ok.
 
Same tactic to skin that cat on my gearbox, No inner gasket. Good clean faces with good sealant. Merry xmas.
 
Yes , .070" end play with gasket, .055" without gasket...........yes, a lot of end play.
That is my concern. So, I am looking to place shims in other places, rather than all out of kick starter engagement.

I will be checking the end play on the main shaft. What is standard method of measuring main shaft end play?
 

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I notice that the way the way this '0.070' end play is bearing measured is poor as you are also measuring any tolerance in the kick start shaft and maybe not all the play in the layshaft. I feel this could result in disaster if the 0.070'' is shimmed out. As for the 'advised' shimming position on the schematic, again not an ideal place to shim the play as the shaft will be effectively be moved into the gearbox. I think that the best idea would be to strip back what you have done and check it - something is amiss here to get such a large figure. The kick start shaft alone underwent 7 different revisions so using a DTI on the end of it may not give a true reflection of just the layshaft end float.
 
Madnorton said:
I notice that the way the way this '0.070' end play is bearing measured is poor as you are also measuring any tolerance in the kick start shaft and maybe not all the play in the layshaft.
Click to expand...

It's the usual tried-and-tested method of checking layshaft end play.
https://www.oldbritts.com/gearbox_a.html
Norton AMC gearbox 4th gear bushes



Madnorton said:
I feel this could result in disaster if the 0.070'' is shimmed out.
Click to expand...

Why?

Madnorton said:
As for the 'advised' shimming position on the schematic, again not an ideal place to shim the play as the shaft will be effectively be moved into the gearbox.
Click to expand...

The head of the kickstart shaft and also the shims shown in the "advised position" are 'inside' the main gearbox cavity.
Norton AMC gearbox 4th gear bushes
 
Norton AMC gearbox 4th gear bushes


This is how I shimmed mine when I fitted the roller. by the time I'd reduced the free play to less than 0.015" I couldn't get my RGM kickstart to fit any more as the shaft was migrating further into the gearbox. I re-checked it after 6 months and the free play had increased, so I binned the roller in favour of a Hemmings high capacity ball-race, which restored the positive location of the layshaft and got the kickstart shaft back where it belonged. It also allows the layshaft to whip around without the bearing cage falling apart

Norton AMC gearbox 4th gear bushes
 
Already answered from experience it seems! The 'advised' position in the schematic would be the better place to shim as it sits on the correct side of the machine datum for the gearbox shell. When you measure the end float on the kick start shaft there are several tolerances that are being measured over different machine datums, ie those for the layshaft, the kick start shaft, the inner cover gasket thickness and the inner cover itself.

Effectively measuring the kick start shaft end float to the layshaft is what is being measured. When the measurement is done in the manor above you can not see in the box as to what is moving in relation to what, and thus needs to investigated further when such a large end float figure is being obtained. Shimming for shimming sakes to remove this large end float without knowing where or why it is occurring is not good practice.
 
Madnorton said:
When you measure the end float on the kick start shaft there are several tolerances that are being measured over different machine datums, ie those for the layshaft, the kick start shaft, the inner cover gasket thickness and the inner cover itself.
Click to expand...


What's being measured is the total end float of the layshaft and kickstart shaft assembly within the gearbox cavity. Gasket thickness, and inner cover thickness seems irrelevant.




Madnorton said:
Shimming for shimming sakes to remove this large end float without knowing where or why it is occurring is not good practice.
Click to expand...

I don't believe anyone suggested shimming without checking the internal components for wear etc., but we obviously know "where" the end play is, but I'm not sure that amount is excessive, however I don't know of any instance where shimming in the usual way has ever resulted in "disaster"? Fitting the drive-side roller bearing upgrade seems to result in increased end float.
 
From Lab's comments we can safely establish, we know that the with original bearings we know what end float measurement works, as proven by many of us each day. It is also known that using the roller bearing gives increased end float. We also know that this modification works.

What we don't know, but there must be many out there that have the knowledge having done this mod, what is the starting end float prior to shimming to get the desired end float measurement, and where did they shim to get the correct figure. If anyone bothered to take and record readings, I'd be surprised, anyone that has would be welcome to enlighten us.

What we also don't know if 0.070'' is actually a problem when using this roller bearing - it maybe OK, but I doubt it, shimming to remove this amount of end float may also be OK, but as one poster has found out it incurs another problem.

Testers always welcome!!!
 
Madnorton said:
What we don't know, but there must be many out there that have the knowledge having done this mod, what is the starting end float prior to shimming to get the desired end float measurement, and where did they shim to get the correct figure. If anyone bothered to take and record readings, I'd be surprised, anyone that has would be welcome to enlighten us.
Click to expand...

Old Britts recommends shimming to 0.005" - 0.010" when fitting the drive-side roller. Apart from that, there's no published optimum or maximum end-float dimension as far as I know, although there has been some controversy in past discussions about whether reducing end float to a minimum is entirely necessary or not. If I remember correctly, the main argument for reducing end float to a minimum seems to be in preventing the box jumping out of 1st gear.


Madnorton said:
What we also don't know if 0.070'' is actually a problem when using this roller bearing - it maybe OK, but I doubt it, shimming to remove this amount of end float may also be OK, but as one poster has found out it incurs another problem.
Click to expand...

The poster was referring to a non-standard kickstart and the problem wouldn't have occurred with a standard K/S lever, I don't think it would have prevented him from grinding the inside face of the non-standard component down a little if it was found to be necessary.
 
I am concerned about this discussion as I did not note any difference in width between the new roller bearing and the old ball bearing.
The roller easily floats, but the old ball system was a tight fit for the layshaft.

The main shaft gets pulled and anchored to the kick side ball bearing , leaving an end float distance between the 4th main gear and the mainshaft.
I was concerned about this main shaft distance being notable and then the pushing of the layshaft in the opposite direction with the advised shims.
So I did ask what was the usual method of measuring/considering this main shaft end float or distance, but since then I think, the gears can be stripped away using only the main shaft and housing to determine how far the main shaft will be pulled in to the ball bearing.

It is indeed great to hear all of the discussion so far, Thank you to all.

The green location noted in my drawing as a possible another location for shim is not correct as this a high rotation location.....but shimming the (pressed in and looks difficult to get out) kickstart shaft bushing would indeed be another shim location.

Norton AMC gearbox 4th gear bushes
 
So I measured the main shaft play and find .051" with no gasket, this would be with a gasket (.015") in place about .066" clearance.
checking this main shaft play was easier than I expected, could be done by hand with a new bearing on kick side.
I am not sure how the two shafts relate, given this info - layshaft with .070" end play ......main shaft with .066" clearance.
It seems to me, at this time, as ignorant as I am, that pulling the main shaft up to the kick side and pushing the lay shaft the other direction is not logical.
I do not know how the shift forks and camplate reference into all of this.
 

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p400 said:
So I measured the main shaft play and find .051" with no gasket, this would be (.015") with a gasket in place about .066" clearance.
I am not sure how the two shafts relate, given this info - layshaft with .070" end play ......main shaft with .066" clearance.
It seems to me, at this time, as ignorant as I am, that pulling the main shaft up to the kick side and pushing the lay shaft the other direction is not logical.
I do not know how the shift forks and camplate reference into all of this.
Click to expand...
Leave the gasket out shim to get around .025 that's worked for me.
 
L.A.B. said:
Madnorton said:
What we also don't know if 0.070'' is actually a problem when using this roller bearing - it maybe OK, but I doubt it, shimming to remove this amount of end float may also be OK, but as one poster has found out it incurs another problem.
Click to expand...

The poster was referring to a non-standard kickstart and the problem wouldn't have occurred with a standard K/S lever, I don't think it would have prevented him from grinding the inside face of the non-standard component down a little if it was found to be necessary.
Click to expand...

Not strictly correct - If I'd 're' re-shimmed the assembly a standard kickstart would no longer fit - it was already rubbing on the gearbox casing, hence why I re-checked and ultimately got rid of the roller bearing.
I suspect the layshaft had been butting against the bush inside the kickstart shaft which then wore and increased the clearance - based on the available evidence.

The roller bearing is clearly better than the original ball-race, but as the above posts demonstrate it brings its own issues. Having discussed this with Mick Hemmings it made my mind up fairly quickly.
 
B+Bogus said:
I suspect the layshaft had been butting against the bush inside the kickstart shaft which then wore and increased the clearance - based on the available evidence.
Click to expand...

But, the layshaft doesn't butt against the inside (did you actually mean the inner face of the bush?) as layshaft 1st. is between them so it's layshaft 1st. that runs against the end of the bush. The outer end of the bush "inside" the K/S shaft is open-ended (see drawing).

Norton AMC gearbox 4th gear bushes
 
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