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Camshaft sprocket end float

Submitted by jake_lomax on Sun, 08/09/2013
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Heavy Twins

Routinely checking the camchain tension on my 650ss, I noticed some endfloat on the camshaft sprocket. I have the revcounter style drive nut on the end of the camshaft and on closer examination I can see the internal surface of this nut is tight up against the end of the cam shaft and doesn't quite reach the cam shaft sprocket, resulting in free play of the sprocket.

I checked my owners workshop manual and there is no mention of any play when refitting the camshaft sprocket. Do I need a washer on the end of the camshaft to take up this free play?

Thanks.

Submitted by phil_hannam on Mon, 09/09/2013

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Jake

There is something not right here. The sprocket should pull up hard against a shoulder on the camshaft with no play when the end nut is tightened.. From memory, I would say that the threaded section of the camshaft then goes into the sprocket by about one thread. There is generally no need for a washer as the drive nut should have a rounded end which pulls up against the sprocket.

See attached photo for variations of Dommie camshaft and nuts. The dynamo engines used a fairly chunky washer behind the combined sprocket/fibre pinion.

Attachments photos-219-jpg

Submitted by steve_marshall on Mon, 09/09/2013

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Previously phil_hannam wrote:

Jake

There is something not right here. The sprocket should pull up hard against a shoulder on the camshaft with no play when the end nut is tightened.. From memory, I would say that the threaded section of the camshaft then goes into the sprocket by about one thread. There is generally no need for a washer as the drive nut should have a rounded end which pulls up against the sprocket.

See attached photo for variations of Dommie camshaft and nuts. The dynamo engines used a fairly chunky washer behind the combined sprocket/fibre pinion.

Submitted by steve_marshall on Mon, 09/09/2013

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Jake, if it's like the 88/99 camshaft driven breather, with the timed breather disc at the T/S end, the cam seemingly has a lot of end float.You should be able to push the cam in and out a few mm (3 or 4) against the breather spring. I can definitely feel this spring action on my own 99. Of course, if the 650SS breather is completely different (and Norton tried a few types over the years on the heavyweight twin/Conmmando) please disregard this MS.

Steve

Submitted by jake_lomax on Tue, 10/09/2013

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Excellent info Gents, thanks. Phil your comment on variations of nuts, and the helpful description and photos got me thinking maybe the tachometer drive nut is the wrong one. So I measured the internal depth of the nut, and compared that to the length of exposed thread on the end of the shaft. The difference is about 50 thou. So I think I need to source a deeper nut, or what are peoples opinions on fitting a washer to take up the clearance?

Submitted by phil_hannam on Tue, 10/09/2013

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Fit a nice chunky washer....that's what I would do. Then torque up the nut to around 70ftlbs.Do a finalcheck of thecamshaft sprocket for any play.

The spring on the end of the breather valve will allow the whole lot to move in and out about 4mm.

Worth noting here.......many owners have had a similar problem with the rotors on alternator powered dommies. ie. the mainshaft nut is tightened but the rotor is still able to move along the crankshaft. The cure is almost the same but this time with a good strong spring washer sitting on top of a chunky plain washer to help remove any play.

 


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