Camshaft Endplay

Putting together a '73 850 and just nipped up the cam shaft nut. I see I'm getting around 0.03" endplay, which seems excessive. Yes the thrust washer is in place. What is the consensus here? What should the end float be? Thanks! David

Around 0.011 / 0.012" is normal for new parts on an 850.

Edit.
0.03" / 0.762 mm
0.012" / 0.305 mm

It might depend on the condition of the outer end of the camshaft bush if an original part.
That is a new AN bush.



With the sprocket up against a hard shoulder and inner beveled washer against the tachometer scroll, under normal circumstances the bush width would control end float.

Thanks for the input. It's all used parts, so I guess the bush is worn. Replacing would require a line bore I think. Any other solutions?
-- David

I edited that post maybe as you were posting.

I think if the bush was worn it would normally be on the bore (that was my experience, bore and cam journal corrugation so I replaced both bushes and line reamed them)




Does the outer end of the T/S bush protrude from the engine case and drive sprocket definitely seat on the camshaft shoulder.

napanorton said:

Thanks for the input. It's all used parts, so I guess the bush is worn. Replacing would require a line bore I think. Any other solutions?
-- David

Click to expand...

If there's no detectable up and down movement of the camshaft and it runs smoothly, see the picture in post #2 of this thread: Is the beveled thrust washer pointing towards the tach drive threads? Is there noticeable wear on the drive side of the timing side camshaft bushing? Has the camshaft sprocket been contacting the crankcase? Is the camshaft sprocket fully seated? Do oyu have the crankcases fully tightened? If all that is OK, I would ignore the end float. In operation it's not going to be moving side to side much, if at all. You can verify that everything clears by turning the cam while pushing in on the sprocket and then while pulling out on it.

Changing the timing side bushing is easy - getting the cam to go back in and turn - not so easy! It will start an argument if I tell you how I do it, so PM me if you really think you need to. Changing the drive side is a nightmare to be avoided unless absolutely required.

Thanks to all. To honest, since I was just "putting it back together"- hadn't changed any parts, I really didn't inspect. My bad. So I guess for my haste, I now get to tear it back down and check the thrust washer, timing side bush, etc.

I guess it's just as well the pistons aren't on yet.

Hmmm. Thinking, so that'll be #2. I hear 3rd times a charm...

Hoping for a prompt decisive conclusion.
Expecting a Norton adventure

-- D

The drive side bush is easy to machine out and to line ream after installation along with the timing side bush.
The beveled washer would make little difference to the end float either way, all that would happen if reversed is the tachometer drive gear would clash. (most likely)
The cam shaft end float could be checked with the single right hand case only (There is a large gap from the camshaft end to the D/S bush which does nothing as far as end float in operation being all done at the T/S.

If you have over double the normal end float (from a new bush) something is worn most likely.
The bushes are easy enough to remove, install (with the oil feed holes lightly chamfered at the OD to avoid more gouging as from the factory and to avoid pick up and reduction of the ID ) and line ream but the tools to that would be rare unless you make them yourself.
Unless something is very wrong or not seated, wear to the bush end as per post #2 would be a likely easy cause.

I would not change a bush unless you were experienced in scraping to size on non porous (when unable to line ream) over some form of abrasive material removal.
The set up is a little odd (850) in having no real thrust face at the outer and only the end wall thickness of the bush, unless the lobes could cause a problem with 0.03" it is probably not worth worrying about (unless you have the tooling to make things as new again and either way they would still go round and round.

(The picture in Post #4 has the camshaft hard to the drive side having no sprocket at the timing side, there would be a large axial clearance to the bush fully assembled)

Time Warp said:

The drive side bush is easy to machine out and to line ream after installation along with the timing side bush.
The beveled washer would make little difference to the end float either way, all that would happen if reversed is the tachometer drive gear would clash. (most likely)

Click to expand...

Not all have the machine tools and equipment to machine out the drive side bushing and/or line ream the timing side bushing.

When installed backwards the beveled washer can enter the chamfer that exists in some timing side bushings and increase the end float. Even if the chamfer isn't there, over time it can wear into the bushing, again increasing end float.

Just to be clear - the beveled washer is installed correctly - I can see it. So I'm going with either a) Gear not seated correctly or some other assembly issue or b) bush worn. If it's a worn bush, I'll probably leave it alone as I don't want to line ream. This will be a normal old street bike. I was concerned the excessive end float affecting the Trispark in a less than optimal way...

Knock the bush out, put a shim behind the flange and knock the bush back in trapping the shim between flange and crankcase. No need for line reaming.

Shimming the bush will simply decrease protrusion at the sprocket side, it will have no effect on end play.

Edit.
Just to make that clear, shimming the bush between the inner flange and engine case will simply move the camshaft to the drive side the amount of shimming, the end float would remain the same.
The exception would be if the shim was enough to move the outer side of the bush into the bush tunnel in the engine case which would mean the inner side of the sprocket would be able to rub on the engine case itself and not on the protruding body of the bush as per standard.

It comes back to the condition of the outer end of the bush and seating of the sprocket on the hard shoulder of the camshaft, 0.762 mm end float seems a little excessive and will have a root cause.

Why did I make the tooling to ream new bushes (days to make, minutes to line ream) , there was no choice, no one could do it so had to do it myself.
That situation does not improve by the day in general.

I had a chance to take the timing sprocket off and found that basically the end play is controlled by difference between the shoulder on the cam and the bushing width. It looks like my bushing is worn and allowing a bit more play. Such is a 50 year old motor with (I assume) the original bushing...



As you can see the cam is proud of the bushing by about 0.030". Shown here the cam is pushed hard up against the bevel thrust washer. So I guess the fix for this would be to replace the timing side bush, which I probably won't do - unless the general consensus is "You have to be kidding - no one would run that!",

Hope it stays together.

-- David

napanorton said:

I had a chance to take the timing sprocket off and found that basically the end play is controlled by difference between the shoulder on the cam and the bushing width. It looks like my bushing is worn and allowing a bit more play. Such is a 50 year old motor with (I assume) the original bushing...

View attachment 84927

As you can see the cam is proud of the bushing by about 0.030". Shown here the cam is pushed hard up against the bevel thrust washer. So I guess the fix for this would be to replace the timing side bush, which I probably won't do - unless the general consensus is "You have to be kidding - no one would run that!",

Hope it stays together.

-- David

Click to expand...

*IF* I understand your picture correctly, you have two bushings - MKIII style (06-5428) and your picture is from the timing side. I just measured the flange on two new ones from AN. They are .063" thick. You can measure yours and see if they are worn.

To see if there's actually a problem, put the timing cover on with the gasket, pull the cam towards the timing side, and see if it is in tolerance for the Tri-Spark stator. Tri-Spark specifies a gap between 1.4mm and 2.6mm (.055" - .102"). IMHO, nothing else about the end float matters since there is no binding.

It’s a 73, not a MKIII, so has the 06-3020 bushing. Guess I’ll have to see how things line up for the Trispark.

napanorton said:

It’s a 73, not a MKIII, so has the 06-3020 bushing. Guess I’ll have to see how things line up for the Trispark.

Click to expand...

A 73 can have the two bushings. What angle did you take the picture from? If it's from the timing side looking towards the drive side and you have a single bushing, it's in backwards. Best to take it apart and show us the bushing from both sides.

napanorton said:

I had a chance to take the timing sprocket off and found that basically the end play is controlled by difference between the shoulder on the cam and the bushing width. It looks like my bushing is worn and allowing a bit more play. Such is a 50 year old motor with (I assume) the original bushing...

View attachment 84927

As you can see the cam is proud of the bushing by about 0.030". Shown here the cam is pushed hard up against the bevel thrust washer. So I guess the fix for this would be to replace the timing side bush, which I probably won't do - unless the general consensus is "You have to be kidding - no one would run that!",

Hope it stays together.

-- David

Click to expand...

I can't imagine how the bush protrusion would wear down like that but the camshaft journal shoulder looks like it has been damaged also so might be connected in some way (beaten on in the past)




Personally I would replace the bush. (Dyno Dave posted he has never had to ream a new bush in 80 years (iirc) so you might be lucky)

One might wonder what the rest of the engine looks like based off that picture.

napanorton said:

I had a chance to take the timing sprocket off and found that basically the end play is controlled by difference between the shoulder on the cam and the bushing width. It looks like my bushing is worn and allowing a bit more play. Such is a 50 year old motor with (I assume) the original bushing...

View attachment 84927

As you can see the cam is proud of the bushing by about 0.030". Shown here the cam is pushed hard up against the bevel thrust washer. So I guess the fix for this would be to replace the timing side bush, which I probably won't do - unless the general consensus is "You have to be kidding - no one would run that!",

Hope it stays together.

-- David

Click to expand...

I don't know if this sheds any light on your issue (which I hope you have resolved) but on the 1973 750 engine I am working on I believe I have the same timing side bushing as yours. Single bushing with no flange. The difference is, my bushing is not proud of the crankcase as yours appears to be, and I have a bronze thrust washer that goes between the cam sprocket and the crankcase. The cam journal shoulder is slightly proud of the crankcase when the cam is fully to the right. So this thrust washer (06-2601) is outside the crankcase and is identical to one that is inside the crankcase between the bushing and beveled thrust washer (06-1086).


In the MIck Hemmings DVD he says that the 2 bronze thrust washers should be used if the timing side bushing is the type that does not have the flange that @marshg246 referred to and @Time Warp showed in post #2. Mick recommends cutting off the tabs, though.

With the configuration I have, I believe end float is set by the the amount that the cam journal remains proud of the external bronze thrust washer. Measured end float is .031", about the same as you had, but it would be a lot more without the external thrust washer.

Thanks for the above topic and info. As a new member here I have been scratching my head over the same question of end float. It is now all clear! My bike should have 2 thrust washers, 1 either side of the bush-and it hasn't. This explains not only the excessive float mine had but may also give a hint as to how the previous owner wrecked the new Wassell ignition rotor he'd fitted. The tiny magnets were stuck to the pick up plate poles having been knocked off due to no clearance. Happy daze, thank you!

Norton's seem to run pretty good with a bit of end play, just my opinion, they weren't perfect from the factory.