Gearbox leak from camplate spindle

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springer

springer

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My gearbox is newly fully refurbished with all new parts. I have a small leak at the kickstart shaft which i will treat either with a quad ring or i will machine the outer cover for a MK3 seal. Any ideas also welcome.
I have however a somewhat bigger leak at the camplate spindle bolt. There are two new o rings in there so i am not sure if i change them there will be any improvement. any ideas how to cure this?
 
It should have been cured by new O rings, if not then you have to look further, maybe the spindle is too long and the O ring is not having any pressure applied, the bush has moved in the case or there is a burr somewhere.
 
Does the O-ring stand proud of the counter bore it sits in? If not, then I won't compress and seal. Also look for defects in the shaft of the camplate and the surface of the counter bore.
 
Thanks, it is still on the gearbox and bike, i was thinking before removing it, to see if there are alternatives (o rings or something else) to buy before i disassemble . Also it is in a Seeley frame so not very easy to take out the gearbox. All parts are new including the shell, bushings and camplate. I assembled it myself and everything seemed good at the time. I will collect any answers and when i remove it i will inform the thread.
 
I put new o-rings in my ‘72 gear box spindle and it also still leaks. Wonder if the vendor is selling the wrong cross section rings. By the way I was able to replace them without removing the gearbox in a standard Commando frame.
 
springer said:
I have however a somewhat bigger leak at the camplate spindle bolt. There are two new o rings in there so i am not sure if i change them there will be any improvement. any ideas how to cure this?
Click to expand...

"Change them"?
There should be one O-ring on the camplate spindle and another on the quadrant spindle.
 
L.A.B. said:
"Change them"?
There should be one O-ring on the camplate spindle and another on the quadrant spindle.
Click to expand...
Yes, you are right, i was talking about both of them being new and if i take the gearbox out , or have access maybe again change them both.
I believe if i can take out the right engine plate , i ll be able to have access without removing the gearbox.
 
After I rebuilt my GB, following Mick Hemmings excellent DVD on the subject, I found leaks at those same locations. Mick did state to have the bushings pushed in just enough to permit the o-ring placement...but nothing specific on how much/or how little that spacing needs to be. What I think it happening, the washer under the spindle bolt is not being put in good contact with the o-ring sitting in the casing. It's like the bolt will not go in spindle any further to allow some ring compression to occur. My temporary solution was to fit a second o-ring under the washer to act as another layer of sealing. Managed to do this without taking anything apart, just stretching an o-ring over the wsher and to the underside. Seems to be helping alot.
Can silicone sealant be used here? I would guess the washer/bolt rotate with the spindle so sealants might only reduce leaks some and still allow rotation.
 
Tornado said:
After I rebuilt my GB, following Mick Hemmings excellent DVD on the subject, I found leaks at those same locations. Mick did state to have the bushings pushed in just enough to permit the o-ring placement...but nothing specific on how much/or how little that spacing needs to be. What I think it happening, the washer under the spindle bolt is not being put in good contact with the o-ring sitting in the casing. It's like the bolt will not go in spindle any further to allow some ring compression to occur. My temporary solution was to fit a second o-ring under the washer to act as another layer of sealing. Managed to do this without taking anything apart, just stretching an o-ring over the washer and to the underside. Seems to be helping a lot.
Can silicone sealant be used here? I would guess the washer/bolt rotate with the spindle so sealants might only reduce leaks some and still allow rotation.
Click to expand...
Sealant won't work. The first time you change gears, the sealant will break free from the shaft. To seal properly, the flat washer must compress the O-ring somewhat. I would guess .030" - .060". To avoid disassembling the gearbox, I would fabricate a thicker flat washer with a counter bore the diameter of the shaft plus .010" - .040" to the depth required to achieve the needed "crush" on the O-ring. Or, if an O-ring of the next thicker cross section will fit, that would also work. I'm not confident that a thicker O-ring will fit in the counter bore in the gearbox case.

Upon further review, I realize that a custom washer may also have to be relieved so as to not rub on the gearbox case. Another idea would be to see if a proper oil seal exists which could be installed in place of the O-ring. [not likely]
 
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chaztuna said:
Sealant won't work. The first time you change gears, the sealant will break free from the shaft. To seal properly, the flat washer must compress the O-ring somewhat. I would guess .030" - .060". To avoid disassembling the gearbox, I would fabricate a thicker flat washer with a counter bore the diamter of the shaft plus .010" - .040" to the depth required to achive the needed "crush" on the O-ring. Or, if an O-ring of the next thicker cross section will fit, that would also work. I'm not confident that a thicker O-ring will fit in the counter bore in the gearbox case.
Click to expand...
Can the bolts be removed (for fitting new o-rings/thicker washers etc.) carefully from spindles without having the cam plate/selector jumping out of place within the GB?
 
Tornado said:
Can the bolts be removed (for fitting new o-rings/thicker washers etc.) carefully from spindles without having the cam plate/selector jumping out of place within the GB?
Click to expand...
In the case of the cam plate, the answer is yes. The shift forks and shift fork shaft will hold the cam plate in position.
 
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Tornado said:
After I rebuilt my GB, following Mick Hemmings excellent DVD on the subject, I found leaks at those same locations. Mick did state to have the bushings pushed in just enough to permit the o-ring placement...but nothing specific on how much/or how little that spacing needs to be. What I think it happening, the washer under the spindle bolt is not being put in good contact with the o-ring sitting in the casing. It's like the bolt will not go in spindle any further to allow some ring compression to occur. My temporary solution was to fit a second o-ring under the washer to act as another layer of sealing. Managed to do this without taking anything apart, just stretching an o-ring over the wsher and to the underside. Seems to be helping alot.
Can silicone sealant be used here? I would guess the washer/bolt rotate with the spindle so sealants might only reduce leaks some and still allow rotation.
Click to expand...
This is a nice theory, probably that is what is happening, i emailed Mick Hemmings because, i got many parts including my 5 speed Quaife gear cluster form him and he recommendd also to try some silicone sealant, if the leak is small (or the gap needed to compress the o ring) it may help. that is if i don t want to take out the gearbox and maybe move the bushings. I am thinking also a slightly thicker o ring maybe that can fit? Or a second o ring as you did but after removing the washer?
 
springer said:
any ideas how to cure this?
Click to expand...
The oring is theoretically held between two components to seal "the gap".
What are the components?
1. The bottom of the counterbore of the aluminum case is one and is not changeable...it is fixed!
2. The second object is the flat washer on the end of the shaft, held by the bolt.
The washers position is fixed to the shaft, but the shafts position is moveable. So the clearance is not assured. A leak can occur if there is a gap.
2a. The brass bushing position is variable and moveable during assembly. The final position of the bushing, therefore the shaft that holds the washer is critical.
In this case it is likely the bushing was not pushed inward enough to pull the sealing washer close enough to the case and be holding the oring in compression.
It is thought these nortons are "simple" however simple does not mean the component assembly position is not critical.
Did the Mick H video tell this little bit?
 
www.accessnorton.com

Kickstart Shaft Seal Tutorial

I don't recall what seal I used when I rebuilt the gearbox on my 750. I think I just used an O-ring. https://www.accessnorton.com/NortonCommando/gearbox-teardown-with-plenty-of-pictures.5107/post-53593 The 850 is definitely leaking and it's got an O-ring. I picked up some SKF 9815 (actually not...
www.accessnorton.com www.accessnorton.com
 
So most of you were right, About an hour's worth of stripping down to get access to the bolt. It seems the bushing is too fa inside. Nw i have to decide if i ll take the box out and push the bushing out or use other means like an oversize o ring. I ll see tomorrow if i can find something that protrudes out of the hole and makes good seal. It seems that i ve overlooked that point when building the gearbox, after all it was my first time and it was a 5 speed too!
Posting the pics , maybe the thread will be of some use to somebody in the future. Thanks also to Angela and Mick Hemmings for their help and advice one more time, They are both great!



 
Hmm i was thinking of the opposite, that i had to pull out the bushing. So maybe i can push the bushing without removing the gearbox?. i also got an O ring which is fatter by 0.5 mm than the previous, i will test to see ho much it sticks out. How much should the O ring be stcking out in order to be compressed and provide a seal?
 
springer said:
How much should the O ring be stcking out in order to be compressed and provide a seal?
Click to expand...

It isn't a matter of how far the O-ring "sticks out" but how much it is compressed by the camplate spindle washer which is dependent on the position of the bush as dynodave said.

In your third photo (#53), the camplate spindle looks as if it is projecting further than the O-ring? If so, then it's unlikely the O-ring would have been compressed.

Assuming the washer isn't already touching the casting when the bolt is tightened with no apparent end float (can't tell from the photos) then the bush needs to be moved inwards which will increase the washer compression on the O-ring.
 
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The end of the shaft is definately higher than the outer edge of the o-ring
 

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