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Camshaft Endfloat

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I am close to assembling the crankcase on my 72 Commando. I have just done a dry assembly with a new standard camshaft with new thrust washer and I have a lot of endfloat- around 70 thou.

I can’t find any info about cam end float in any of the manuals, but thought it would probably be nearer to 10 thou. Nobody as far as I can see sells different thickness thrust washers or shims for this, so perhaps cam end float isn’t critical.

As an extra check, I fitted the cam sprocket and intermediate gear, and the two sprockets are in the same plane when the camshaft is pulled to the right, to be tight on the thrust washer. Also with the cam in this position the lobes are sitting nicely on the cylinder rocker lifters.

Is this big end float normal?

Do I need another thrust washer on the camshaft inside the timing case?

Or does the pressure of the camshaft pushing against the Tacho drive push the camshaft to the right?

I would appreciate other Members advice and experience on this.

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Seem to remember the last time I answered this question on here it was 10 thou but worth waiting for someone to confirm or searching for the thread.

As it's a 72 you need to get rid of the 2 stupid thrust washers that had detachable location tabs that were sized perfectly to jam the oil pump and us the standard thrush washer with the heavy chamfer on the inside next to the timing side. As there should be two 72 type washers, if you are only using 1 that explains the excessive end float. The standard one is double the thickness of a single 72 washer.

Also if you are using a new cam the camshaft bushes or the cam journals must be scrolled, both can be scrolled but never use plain bushes with plain journals. 

With 10 thou endfloat the direction of the camshaft's travel is not an issue, it will change from one side to the other from acceleration to deacceleration anyway.

Found it

https://www.nortonownersclub.org/node/12507

6 to 10 thou

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The lack of any published evolution about the NHT leaves many questions asked and often unanswered.

The evolution from 20M3 (twin chain timing chest) to 20M3S (single timing chain  timing chest) makes a change that I accept but seems to be in generally ignored .

The inboard tach drive that came with the 20M3S changed the cam to have a spiral drive gear ON the cam with It's more complex manufacture. That part of the process is hopefully understood.

The part I want to bring up is that the 06-1086, called thrust washer, it's  function is identical to the prior cams fixed thrust surface. How ever it had to be manufactured separately.  from 71-on EVERY cam needs the 06-1086 spacer and it's dimension should be not altered or even  considered for modification.

20M3S-200000-300000-325000, each series had it's own style of thrust and position orientation. within it's own cam bearing function.. Each of those 4 families were different with the 200000 series being the worst of them all.

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Quite a variation although I,ve no idea of what all those strange numbers mean!  The 06-1086 thrust washer is current for my Mk3 850 but gave the wrong endplay for my setup.

Easily sorted however. I just checked the cam lobes were central to the followers and hand lapped the thrust washer to give 0.006" clearance with the sprockets lined up on the same plane. Eleven years later and on the second cam (the excellent standard type Web #312) it,s still there with the same camchain and rubber faced adjuster. This gives a quiet and efficient operation with cam chain play set around 4mm max.

Steve,  0.070" is way too high and needs looking at but check you have the correct cam bushings for your engine and go from there. May need a bit of mix and match to get the 0.006"-0.010" 

 

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Knowing something about the progression of the NHT evolution would help improve the results of "would be mechanics".  This is what I strove for.

As shown below the current sample of my research subjects. It is every major version of norton engine except hybrids and an alternator 14 (99). The 25 engines currently sit on several display tables behind me in my office. In addition I own 14 various commando, 4 slimline and 2 gardengate/model 7 (1 Dunstall atlas +1 71 Dunstall commando)

The advice givers will sometime show their complete lack of knowledge. It some time frustrates contributors who will then be  denigrated and finally be driven away. I have departed a number of internet norton forums and will now be on one less.

12D 122D 122A 14D (no14A) 650 all domi in front line

20M1 20M2 20M3 20M3S 200000 300000 325000 in rear

NHT family

 

 

 

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Sorted out my problem. Needed 061086 and 062601 washers inside the crankcase and a 061601 washer on the end of the camshaft inside the timing case. This gives me 9 thou endfloat so all good.

Cam lobes lined up nicely with my resurfaced cam followers. Attached a pic to show this.

Thanks to John, David and Neil for the advice and information.

David, blown away by your Heavy Twin collection. The knowledge you must have! You should write a book!

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The very early Commando had a camshaft similar to that of the Atlas. So one end had a round shoulder which was pulled up against the inner timing case, while the other end sported a breathing disc set-up with an internal spring that helped to keep the camshaft from floating around too much. If this latter item is still part of the later Commando engine set-up perhaps it needs a mention. 

Moving on to the later 750 Commando, with reduced cog timing gear, and we have a scroll-driven rev counter, plus camshaft minus a shoulder but instead a hefty washer to do some spacing.

Further on past engine 200,000 and the Commando Notes say that 2 spacer washers are needed providing the correct chunks are fitted.

In those days Norton Villiers were very proud to tell the world about how accurate their machining was and thus tolerance differences were very low. Which is how it should have been but when I spoke with John Hudson about crankshaft clearances / sideplay he had found these to be anywhere between 12 and 40 thou. Now if the crankshaft was wandering around that much what was the camshaft doing?

In reply to by steve_constable

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Steve, glad you found a solution and got a good result. Is that a Combat cam?

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Hi Neill

No just a standard cam.

David, Hopefully you are still here?  My question is not about end play but rather about camshaft dimensions. I have 3 used cams marked with a T. I'm pretty sure one came from my 850 because i cannot find one in the 850 parts boxes. its easy to measure journals and bushes and how they feel in the case but how do we know if the lobes are worn too much? is there a number one can use to measure top to bottom at the highest point?  One of those cams has rounded shoulders on the lobes, perhaps from some of what Phil called "wandering"? Some of the older cams were of better quality than the current ones available? If i decide i must toss them all whats the best source for a new one? Andover or custom grind? its just an easy ridden road bike not looking to build a hot rod. Ive had all the machine work done but my machinist has passed on.  I seem to recall he thought the cam was ok but now ive mixed them up with  a couple jumble part cams.. 

If David is gone someone else please?

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The lift plus the base circle makes the total measurement. All 1S  cams were the same .889/890".

Only the 2S had a slightly smaller base circle .867/.870 but of course a higher lift being different for int and exh,

You can only approximate the lift by measuring 90 degrees from the lift lobe as every cam except one, you will be measuring a little lift across both ends of the ramps. 

Only the early model 7 cam is SO mild you will not yet be on the ramps.

Reground cams will be much more work to determine what the # are.

 


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