Layshaft: Balls or rollers

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powerdoc

powerdoc

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In the recent post about layshaft re-bearing, the question of using the roller bearing or a ball bearing replacement came up. Apparently the Commando guru says balls, others say rollers. What is the pro/con for a street bike rebuild or is it just a "fielders choice" ?
 
Well...one way to look at is that the original bearings that everyone is so worried about are the ball type...seems to me that the roller type is the upgrade...my two cents

GB
 
There were a run of bad bearing from portugal. You can get a good quality ball bearing to replace the old. This is an easy plug and run option and will work just fine.

Roller bearings are excellent and robust for the application. The issue is shimming the end play.
I do not like the traditional method of putting rear iso shim on the kickstart shaft to accomplish this task.

I believe the proper way would be to place shims behind the outer race against the casing inside like superblend shimming in the crank case versus the shim behind the inner race against the crank cheek.

This would require some assembly to measure and possibly disassembly to adjust, but once set, you are more than likely set for life.
 
pvisseriii said:
There were a run of bad bearing from portugal. You can get a good quality ball bearing to replace the old. This is an easy plug and run option and will work just fine.

Roller bearings are excellent and robust for the application. The issue is shimming the end play.
I do not like the traditional method of putting rear iso shim on the kickstart shaft to accomplish this task.

I believe the proper way would be to place shims behind the outer race against the casing inside like superblend shimming in the crank case versus the shim behind the inner race against the crank cheek.

This would require some assembly to measure and possibly disassembly to adjust, but once set, you are more than likely set for life.
Click to expand...

Please explain WHY you don't like the shimming behind the kicker shaft.
 
Please explain WHY you don't like the shimming behind the kicker shaft.
Click to expand...

Yes correct my logic that it'd be better to have the bearing outer race set deep as can be in the weakly surrounding bore by opposite side shims? Or if no shims handy just remove a gasket or two.
 
Whatever you do , dont buy the cheapest .

The Swedish had the best balls at the time .

Swiss , German or even American would be better than recycled asian ( oops :oops: :p ) scrap metal . Evewn though theyve refind techniques . :lol: :shock:
 
concours said:
Please explain WHY you don't like the shimming behind the kicker shaft.
Click to expand...

The rear iso shims do not fit right over the shaft and requires grinding and trimming to fit. Then there is the radius at the base where the shims would rest so the first shim or two or three would have to be trimmed a bit more than the rest. Then you have the outside dia.of the shim which has to slip in behind in the pawl stop. This ends up being cumbersome, inaccurate and fussy to get just right compared to a ridged stationary setup behind the outer race of the roller layshaft bearing. IMHO

For what ever reason I go into the gearbox, I am going to have to mess with them goddamn shims. If installed proper in the first place, I shouldn't have do deal with them again, theoretically. Again, IMHO.

This may or may not explain, but you asked why "I" don't like to shim the kicker shaft. Well. that's why.

Hobot, Do you really think .020 or .040 worth of shim is going to create undue stresses? The inner is slipping in and out of there all the time anyways. And doesn't shimming as I suggest bring the layshaft in proper orientation (not that .020 to .050 would effect the layshaft orientation) else why the need to shim the kickshaft? Steve, I can't help thinking that you have been really reaching lately.

Beside, I am totally comfortable with the quality ball bearing I have in place. No worries mate!
 
I've got a question for you guys:
There is a lot of mention about axial forces stressing the bearings, and the bearing cage fails due to axial forces, etc. Since all the gears appear to be straight cut
spur gears, where does the axial force come from?
Thanks,
JD
 
jaydee75 said:
I've got a question for you guys:
There is a lot of mention about axial forces stressing the bearings, and the bearing cage fails due to axial forces, etc. Since all the gears appear to be straight cut
spur gears, where does the axial force come from?
Thanks,
JD
Click to expand...
I would say shifting under load, worn bushes, worn dogs forcing gears to slip out and any other issue other than normal curcumstances including poor clutch setups.

Originating from proponants of the roller type bearing, hard shifter and abusers of the AMC gearbox.
 
jaydee75 said:
I've got a question for you guys:
There is a lot of mention about axial forces stressing the bearings, and the bearing cage fails due to axial forces, etc. Since all the gears appear to be straight cut
spur gears, where does the axial force come from?
Thanks,
JD
Click to expand...


There is no axial load on the bearings. The roller replacement positions the left end of the layshaft in the same position as a ball bearing because they have the same dimensions. The correct way to shim the layshaft is between the kickstart gear and the inner cover. This should be checked and shimmed whether you are using a ball bearing or a roller. It sets the depth of engagement for first gear. Jim
 
pvisseriii said:
concours said:
Please explain WHY you don't like the shimming behind the kicker shaft.
Click to expand...

The rear iso shims do not fit right over the shaft and requires grinding and trimming to fit. Then there is the radius at the base where the shims would rest so the first shim or two or three would have to be trimmed a bit more than the rest. Then you have the outside dia.of the shim which has to slip in behind in the pawl stop. This ends up being cumbersome, inaccurate and fussy to get just right compared to a ridged stationary setup behind the outer race of the roller layshaft bearing. IMHO

For what ever reason I go into the gearbox, I am going to have to mess with them goddamn shims. If installed proper in the first place, I shouldn't have do deal with them again, theoretically. Again, IMHO.

This may or may not explain, but you asked why "I" don't like to shim the kicker shaft. Well. that's why.

Hobot, Do you really think .020 or .040 worth of shim is going to create undue stresses? The inner is slipping in and out of there all the time anyways. And doesn't shimming as I suggest bring the layshaft in proper orientation (not that .020 to .050 would effect the layshaft orientation) else why the need to shim the kickshaft? Steve, I can't help thinking that you have been really reaching lately.

Beside, I am totally comfortable with the quality ball bearing I have in place. No worries mate!
Click to expand...


I understand cumbersome and fussy, please help me understand inaccurate :idea:
 
The shimming process is simple even if it does take a few tries to get it just the way you want it. So simple that I did mine without a dial guage. I added shims until I felt friction, then took out 5-thousandths. I then had a perceptable amount of end play. It has been trouble free. If I had done that behind the bearing I would have gone nuts.

Russ
 
rvich said:
The shimming process is simple even if it does take a few tries to get it just the way you want it. So simple that I did mine without a dial guage. I added shims until I felt friction, then took out 5-thousandths. I then had a perceptable amount of end play. It has been trouble free. If I had done that behind the bearing I would have gone nuts.

Russ
Click to expand...

And doing it behind the bearing does no good as far as setting the engagement depth of first gear. The sliding gear is located on the layshaft by the shift fork. The dogs on the sliding gear are moved into first speed countershaft gear to engage first. First speed countershaft gear is located by the kickstart gear which needs to be moved away from the inner cover push first speed gear over and increase the depth of engagement to keep first gear from popping out under hard acceleration. Jim
 
concours said:
I understand cumbersome and fussy, please help me understand inaccurate :idea:
Click to expand...

Anything cumbersome and fussy in tight tolerance situation has an opportunity to be inaccurate.
For instance, if you don't use the same gasket every time and if you don't get the shims situated just so, the measurements can change. If they are not set all flat and tuck nice around the radius, you'll get a bad reading. Drive around the block and recheck and it's too loose. Add a shim drive around the block, getting it all good and warmed up, and it becomes too tight. I don't mind a little loose but when a little tight the kicker will bind and transfer issues all the way down the line, so to speak.


These are not assumption of mine but simply my experiences.
Please keep in mind that this is just my take on it and is absolute only to me and to others along my wave link.

Anything can become a liability if you either under or over think it.
 
comnoz said:
rvich said:
The shimming process is simple even if it does take a few tries to get it just the way you want it. So simple that I did mine without a dial guage. I added shims until I felt friction, then took out 5-thousandths. I then had a perceptable amount of end play. It has been trouble free. If I had done that behind the bearing I would have gone nuts.

Russ
Click to expand...

And doing it behind the bearing does no good as far as setting the engagement depth of first gear. The sliding gear is located on the layshaft by the shift fork. The dogs on the sliding gear are moved into first speed countershaft gear to engage first. First speed countershaft gear is located by the kickstart gear which needs to be moved away from the inner cover push first speed gear over and increase the depth of engagement to keep first gear from popping out under hard acceleration. Jim
Click to expand...

My goodness, you' re treating this AMC gearbox like it was a Swiss watch, which it surely ain't.
How many thousandths does it take to keep first gear in place under load. 5, 10, 15? If the dogs are good and the detent spring is in spec, the gear will climb home and stay there. .010" in either direction isn't going to change that. Neither will a few thou keep a warn dog in place.
I do not believe for one minute that the layshaft was meant to be tuned in any manner in which we speak. Only with the advent of the layshaft superblend did this come about, unless I missed something in the workshop manual (section D9 - D12). The layshaft "should" be stationary, but abuse, poor maintanence and just warn out bushing tend to blow cages apart. Bad design? I don't think so. It is what it is.
If you are going racing....well....thats another topic......and another gearbox.
 
This is decades old quandary. Old school racers liked to use balls on lay shaft and TS crankshaft, shafts that tend to deflect off straight when under hi load, as supposed to take up the end deflection more than a roller before transmitting bind through race into case bore. Replacing a Defective product is the only issue to solve, by ball or roller.
 
pvisseriii said:
comnoz said:
rvich said:
The shimming process is simple even if it does take a few tries to get it just the way you want it. So simple that I did mine without a dial guage. I added shims until I felt friction, then took out 5-thousandths. I then had a perceptable amount of end play. It has been trouble free. If I had done that behind the bearing I would have gone nuts.

Russ
Click to expand...

And doing it behind the bearing does no good as far as setting the engagement depth of first gear. The sliding gear is located on the layshaft by the shift fork. The dogs on the sliding gear are moved into first speed countershaft gear to engage first. First speed countershaft gear is located by the kickstart gear which needs to be moved away from the inner cover push first speed gear over and increase the depth of engagement to keep first gear from popping out under hard acceleration. Jim
Click to expand...

My goodness, you' re treating this AMC gearbox like it was a Swiss watch, which it surely ain't.
How many thousandths does it take to keep first gear in place under load. 5, 10, 15? If the dogs are good and the detent spring is in spec, the gear will climb home and stay there. .010" in either direction isn't going to change that. Neither will a few thou keep a warn dog in place.
I do not believe for one minute that the layshaft was meant to be tuned in any manner in which we speak. Only with the advent of the layshaft superblend did this come about, unless I missed something in the workshop manual (section D9 - D12). The layshaft "should" be stationary, but abuse, poor maintanence and just warn out bushing tend to blow cages apart. Bad design? I don't think so. It is what it is.
If you are going racing....well....thats another topic......and another gearbox.
Click to expand...


Shimming the gearbox to prevent first gear problems has been a normal shop practice since the AMC box came to be used on large motors. Long before anyone ever thought of installing a roller bearing on the layshaft. This information was courtesy of Brian Slark many years ago. And yes .010 or .020 means a lot. I have certainly cured many gearboxes that popped out of first with nothing but a few shims. Jim
 
comnoz said:
[Shimming the gearbox to prevent first gear problems has been a normal shop practice since the AMC box came to be used on large motors. Long before anyone ever thought of installing a roller bearing on the layshaft. This information was courtesy of Brian Slark many years ago. And yes .010 or .020 means a lot. I have certainly cured many gearboxes that popped out of first with nothing but a few shims. Jim
Click to expand...

Thank you Jim for the in site. I do value and respect your knowledge and opinions.
 
I have heard lots of different opinions on this and granted there is more than one way to skin a cat.

I was always puzzled when I read an old and well known gearbox instruction that stated that he liked to use a ball bearing because it positively located the layshaft, and then later he said that the shaft was too tight in the bearing so it was good to sand the shaft down until it was a finger push fit into the bearing. I guess the positive locating of the shaft wasn't so important after all???

Oh well- either way will get you there. And then if it pops out of first when you rev it up- stick a shim in there and cure it. I have done it that way too. Jim

PS, There isn't any hard feelings here. But if you know me you know I'm always up for a good argument between friends. Right or wrong.
 
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