Clutch basket play and ? gearbox problems on MK3.

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Reggie

Reggie

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Yesterday I fitted a new clutch centre and bearing to my clutch on my Commando MK3, as the gearbox was difficult to select gears and it was not possible to select neutral whilst the engine was running. I also have a cross shaft and cross shaft bush on order to be fitted next week.

I fitted the bearing by heating the "sproket with backplate." The new bearing which I cooled dropped straight into its housing. After a few minutes, when the bearing had warmed, I gently eased the clutch centre in by hand, with nearly no pressure at all, I assume due to the bearing having expanded. Therefore I don't believe that I have damaged the bearing.

When I mounted the clutch, I was suprised that I could rock the basket with probably 1 to 1.5mm play (my best guess) at the outer circumference. It doesn't sound a lot of play, but I would have thought that there should be zero play.


The other unusual occurance was that as I tightened the clutch centre nut to 40ft/lbs (with the box in second gear and the rear brake on) the kickstart moved backwards at the kick-end about half an inch.

I didn't rebuild the box during the rebuild of the bike, as the box had been re-built at by a well known Norton spares outlet last year for the previous owner, for which I have the reciepts. His problem had been that he had had to select second rear before being able to select first. The major items replaced were the mainshaft bearing and camplate.

Due to needing an outrigger stud which I will not receive until Monday, I have not been able to test my work to see if there is any improvement yet, but am concerned about the clutch basket play, and the kickstart moving backwards when tightening the clutch securing nut.

Does anybody have any thoughts or insight into this?
 
There's usually a little play on the clutch basket, its only supported by one ball race and that bit of compliance helps the clutch work.
The problems you describe could easily be gearbox oil contam on the plates, or one or more of the plates are warped.
The kick start moving is a sign of lay shaft bearing problems but normally experienced when riding. I have tightened my 850's clutch centre as you described a few times and never seen the kick start move. I probably wasn't looking either.
Have you any lateral movement on the gearbox shafts, was the clutch slipping above 4000?
 
I have only just finished re-building this bike and have only covered about 5 miles on it, and it is because of the above problems that I decided to fit a new clutch centre and next week I will be fitting a new cross-shaft and bush.

The clutch basket was empty when I got this movement as I was re-assembling it at the time with the new clutch centre, and as I am running a belt drive, the clutch was completely dry when the problems were apparent on its maiden run when gearbox wasn't at all easy to use. The old clutch centre was notched, but not what I would describe as badly, so I took a chance and fitted it on the re-build, although I am not sure that the new clutch centre will solve the problems. Out of interest I am also running surflex plates.

I cannot feel any lateral play on the mainshaft.

I suppose that I can't be sure of the benefits of the new clutch centre until I have run it next week.
 
Reggie said:
When I mounted the clutch, I was suprised that I could rock the basket with probably 1 to 1.5mm play (my best guess) at the outer circumference. It doesn't sound a lot of play, but I would have thought that there should be zero play.
Click to expand...


The factory manual specifies the use of a 1 dot clutch centre bearing with a 1.5mm corner radius (for the original clutch at least), is that what you have actually fitted?
 
L.A.B. said The factory manual specifies the use of a 1 dot clutch centre bearing (for the original clutch at least), is that what you have actually fitted?

Yes, now I look at the bearing dimensions in the manual, (which I looked at prior to purchase) I notice it says "Deep grove ball bearing-one dot."

I purchased an NSK standard bearing from a local bearing supplier. Oh dear, it looks as though I've just wasted 12.00 pounds! What does the "one dot" mean? I did notice that the old bearing had slightly deeper shoulders than my new bearing but thought that it would be within tolerances for the purpose.

Thank you for that L.A.B. I'd compared the rocking motion on my original clutch wheel...fitted on the mainshaft, with original bearing and it was definately less than this new bearing gave. Looks like I'll be changing the bearing.....again.
 
1 dot means a tight clearance in the bearing, 2 dot is what you get as std without specifying a clearance. 3 dot is extra clearance and is used for bearings in alloy housing with an interference fit and so in the normal temp state are gripped by the housing, if you fit a 2 dot in this situation the bearing binds.

As 1 and 3 dot bearings are made in smaller batches expect to pay more.

Note that the dot system is not used in the US so this does not apply, but the principle of clearances does.
 
It has been well documented that too tight of a primary chain will cause difficult shifting and poor clutch disengagement. I wouldn't think that to be a problem on a standard Mk III primary, but you state that you have fitted a belt drive. Could it be that the belt is too tight?

The kickstart movement you describe doesn't sound too good. Might want to give the layshaft bearing (s) a look-see.

Good Luck,
 
The dot system was the old UK standard used before the ISO standard (read as Euro), they are easily confused and there is the US std too.

CN Normal radial clearance; normally only used together with an additional letter that identifies a reduced or displaced clearance range

C2 Radial internal clearance smaller than Normal
C3 Radial internal clearance greater than Normal
C4 Radial internal clearance greater than C3
C5 Radial internal clearance greater than C4

1 Dot is the same as C2
2 Dot is the same as CN
3 Dot is the same as C3
 
Reggie said:
The other unusual occurance was that as I tightened the clutch centre nut to 40ft/lbs (with the box in second gear and the rear brake on) the kickstart moved backwards at the kick-end about half an inch.

The only possible cause of the kickstart moving is that the layshaft is not turning freely in the bronze bush in the kickstart shaft. The usual cause of this is imminent failure of the layshaft bearing (at the other end of the shaft) which allows the shaft to move out of line and pick up in the bush.

However, if your box is newly built, it could be that the assembler did not ream the bush sufficiently or damaged the bush slightly on assembly.

As earlier postings have suggested, it would be a good idea to open the box and have a look. If the bearing seems OK, just easing the bush a fraction should suffice.
Click to expand...
 
L.A.B. & kommando, thanks to both of you for your highly comprehensivereplies. I never knew about these important differences in bearings of the same size, and the amount of variations available.


jumpjg said.
"It has been well documented that too tight of a primary chain will cause difficult shifting and poor clutch disengagement. I wouldn't think that to be a problem on a standard Mk III primary, but you state that you have fitted a belt drive. Could it be that the belt is too tight?"
Click to expand...

No the belt isn't tight and the final drive chain isn't tight either.

79x100 said
The only possible cause of the kickstart moving is that the layshaft is not turning freely in the bronze bush in the kickstart shaft. The usual cause of this is imminent failure of the layshaft bearing (at the other end of the shaft) which allows the shaft to move out of line and pick up in the bush.

However, if your box is newly built, it could be that the assembler did not ream the bush sufficiently or damaged the bush slightly on assembly.

As earlier postings have suggested, it would be a good idea to open the box and have a look. If the bearing seems OK, just easing the bush a fraction should suffice.
Click to expand...

I am slowly and reluctantly drawing that conclusion myself, although I wish now that I had done it when it was out of the bike. I would have thought though that all this would have been looked at when the box was apart, although that doesn't stop another component failing later. Without checking, I would think that the box has run less than 1,000 miles since its re-build.

Just out of interest, is it possible to do a layshaft bearing with the box in the bike. From memory, I would assume that you cannot heat up the case sufficiently with it in situ? But could you determine if the bearing has had it, and then if necessary take the box casing out to do the job?
 
I have taken a layshaft bearing out of an installed gearbox, took the primary off and belted the gearbox with a rubber mallet to jar the bearing out after heating. Sounds to me that the problem is in the kickstart bush being a bit tight rather than a newly installed layshaft bearing is on its way out.
 
I agree with Kommando on this. One would have to do something pretty brutal during installation of the layshaft bearing to cause such early failure. It may be possible but I've never heard of it.

Were the layshaft bearing and bush replaced during the rebuild ? It would have been necessary to at least remove the bearing for examination and cleaning when the mainshaft bearing was replaced and it would then be rather poor practice not to simply renew them.

On the assumption that the layshaft bush was replaced, then there is a good chance that it is simply a bit tight or has picked up slightly. You should be able to diagnose the problem by removing the inner cover. :)
 
Reggie said:
The other unusual occurance was that as I tightened the clutch centre nut to 40ft/lbs (with the box in second gear and the rear brake on) the kickstart moved backwards at the kick-end about half an inch.
Click to expand...

Reggie,

One point I would like to raise is that you tightened the nut with the box in *second* gear, I think it is generally better to do this with the box in top gear, the Haynes Norton manual and many other Brit manuals - Triumph etc. say *top* gear although I think the Norton factory manual does not bother to mention it (maybe because it was the generally accepted practice?).
With the box set in top gear, the mainshaft is then locked directly to the sleeve gear, so there is no loading placed on the layshaft at all, which I expect there will be if second gear is used (across the second gear set and also top gear (layshaft drive to sleeve gear) set.

Possibly this unnatural static loading of the layshaft while the nut is tightened using second gear could (in some way) be the cause of what you have described?
 
I had the same problem with the first set of surflex plates I fitted. Three of them were warped and not by much, I reckon it was poor storage. The replacement set have been superb and would recommend them for use with any belt drive conversion.
 
79x100 said:
Were the layshaft bearing and bush replaced during the rebuild ?
Click to expand...

No, just the camplate and mainshaft bearing, plus many assorted nuts, seals, gaskets and "o" rings.

kommando said
I have taken a layshaft bearing out of an installed gearbox, took the primary off and belted the gearbox with a rubber mallet to jar the bearing out after heating.
Click to expand...

It has been over 11 years since I have done a gearbox on a Commando, so its good to know that this can be achieved with the gearbox in situ.

L.A.B. said
One point I would like to raise is that you tightened the nut with the box in *second* gear, I think it is generally better to do this with the box in top gear, the Haynes Norton manual and many other Brit manuals - Triumph etc. say *top* gear although I think the Norton factory manual does not bother to mention it (maybe because it was the generally accepted practice?).
With the box set in top gear, the mainshaft is then locked directly to the sleeve gear, so there is no loading placed on the layshaft at all, which I expect there will be if second gear is used (across the second gear set and also top gear (layshaft drive to sleeve gear) set.
Click to expand...

When I had a right hand gear change Commando, I used to always put it in fourth gear to tighten crankshaft/clutch nut etc but it seemed a lot of hassle getting it into fourth gear with the primary outer case off.....so it was poor practice on my part.

Thanks for all of the general guidance. I may well end up having a look at the layshaft bush, if not all of the box. I'll see how it feels after I have it running early next week.

The gearbox was re-built at Norvil, and I notice from the previous receipts that a cross shaft spindle and c/case bushes were purchased, and also from RGM selector forks and camplate . These parts were not fitted (as far as I know) at Norvil during the re-build, but presumably by the previous owner. So it would seem that there has been alot of recent history of trouble with the gearbox. I have only ridden the bike about 5miles when I purchased it, and then last week about 5 miles since the complete (excluding the gearbox) re-build.

I put a new cross shaft connector on the gearbox when I built the bike, but there was still about half an inch of free play in the gearshif pedal. Does this sound excessive or about right?

Cash wrote
I had the same problem with the first set of surflex plates I fitted. Three of them were warped and not by much,
Click to expand...

How did you determine that the plates were warped? Did you use a flat piece of plate glass and some feeler gauges, and can it be done this way?[/quote]
 
Reggie,
I agree with LAB recommending forth gear. In fourth the force will be mainly loaded on the layshaft bearing not the bush and give the rear brake an easier time holding. No slippage no movement. So don't start pulling the box to bits yet.

A quick method to check the plates is;
With two of the surflex plates put one on top of the other simply offer them up to the light and look for a gap. Rotate one of the plates through say 30 degrees and look again. Taking care not to distort the plates. Then turn one over and repeat. Do this with the set and try to check all the plate against each other. If you've got more than one warped plate the gap is doubled and is easily seen. Check the steel set too you never know.
I'd put my money on warped surflex plates.
 
Reggie said:
I put a new cross shaft connector on the gearbox when I built the bike, but there was still about half an inch of free play in the gearshif pedal. Does this sound excessive or about right?
Click to expand...

That sounds about right.
I'm not sure you will be able to get it much better than that. My own was certainly worse before I had a go at it, even though some kind PO had epoxy glued the connector to both shaft splines to try to remove some of the play! That initially caused me a bit of head-scratching as to why I was unable to get the cross-shaft out! In the end I realised what had been done to it, the joint not really being in the most acessible place, but there was just enough room to get a blow-torch to it to free the joint!!
 
cash said:
In fourth the force will be mainly loaded on the layshaft bearing not the bush and give the rear brake an easier time holding. No slippage no movement.
Click to expand...

I cannot see that there should be any real loading on the layshaft at all if top gear is selected? As any loading goes directly from the mainshaft to the sleeve gear (via mainshaft 3rd) the layshaft is, in effect, idling when top gear is selected, top gear being 'direct drive' (1:1) as I see it the main loading will be taken by the mainshaft output bearing.
 
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