camshaft end float

madass140

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I know this subject has been discussed before.
preparing 72 cases for assembly, I have done the oil pick up /breather conversion as per 'Oldbritts"
now the camshaft, I machined a new timing side bush with the flange thickness so it gave the sprockets perfect alignment when the cam is thrusting to the right, the cam then can still move to the left 2mm, so it has 2mm end float, my only concern with this is if this much end float can have any bearing on the ignition.
any idea what thickness the flange is on the bush from later models and is the flange thickness the same as the thrust washer with tab?
 

comnoz

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It certainly could be a concern with some ignitions. I would machine a washer to cut the end float down to .15 to .25 mm. Jim
 

madass140

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when the sprockets are aligned then you would think that there qould be only a few thou clearance (endfloat) between the back of the cam sprocket and case, not 2mm., I think I'll have to fit the outer cover and Ignition to check that there is no problems when the cam is in or out, Has anyone ever checked to see the position of the camshaft when the motor is running, ie: like pushing on the center ignition bolt to see if the cam moves in?
 
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As the factory doesn't/didn't list different size thrust washers I wonder if they worried about it,which way does the tach drive push the cam?
sorry misunderstood were the clearance is, pinion holes not damaged causing misalingment ?
 

madass140

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the tach drive would push the cam to the right side of the bike, whether it actually does no one knows.
when i assemble this engine and have it running I'll determine which way the cam wants to go if any.
 

madass140

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maybe a setup like the earlier models which had the spring loaded rotating breather would be the go. this would ensure the cam is always thrusting to the right ???
 

madass140

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Or, maybe instead of having one flanged timing side bush, 2 flanged bushes on the timing side (inner and outer)would be better, then correct positioning of the camshaft ( sprocket alignment) and end float could be achieved at the same time, This looks like the best option.
 
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What
madass140 said:
Or, maybe instead of having one flanged timing side bush, 2 flanged bushes on the timing side (inner and outer)would be better, then correct positioning of the camshaft ( sprocket alignment) and end float could be achieved at the same time, This looks like the best option.
If my memory serves me well, what you are suggesting with the 2 flanged bushes is what the factory used in the 850 MK3's

After rebuilding my 850 MK2 & fitting new cam bushes there was enough of the new bush (Flange to the inside) poking through on the timing side that there was negative end float.
An old tool maker friend of mine milled the protruding bush down to provide endfloat of about 0.006 thou.

In retrospect, if I were to do it again. I had already decided I would use the method you are suggesting above..

Sweenz
 

madass140

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I ended up machining a new full width flanged bush with the correct flange thickness when the sprockets were aligned.
when the cam is full thrusted against the flange (correct sprocket alignment) the cam had 2mm endfloat , there was 2mm of camshaft journal protruding so I machined a 2mm steel spacer which I later casehardened and fitted that, it had about .002" clearance on the shaft and gave the cam about .004" endfloat, probably not as ideal as the 2 flanged bush setup, but I think it should be ok. I dont forsee any problems occuring , remembering that the cam is thrusting to the right , so my spacer theoretically will never have any load.
 
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Hey Madass,
Sounds good.

I like your logic as it backs up where we went with my setup.
The case hardened steel spacer would also be the ticket to protect the protruding part of my cam bush from wear if there is any cam thrust to the left at anytime.
I will check mine for wear on the end of the prutruding bush when I have the need to check/adjust the camchain.

Can't see you having an issue with the setup you have employed.

Sweenz
 

madass140

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fitting 2 identical bushes back to back is good in theory but there is the chance of slight misalignment of the two bushes, my next thought was to make the second flanged outer bush only 1/4" long at the most eliminating any misalignment problems. I'm sure there will be some negative comments to my fix.
 

Brooking 850

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hi madass140, any chance the you took some pics of the bits before you installed them as in an 'exploded view'?
Regards mike
 

madass140

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no I didnt sorry, the bush was virtually the same as the stock paralell one (which uses the tabeed thrust washer with it) but with a flange to replace the tabbed thrust washer, the spacer behind the sprocket was I guess similar in dimensions to the beveled spacer inboard.
 
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Building an early 750 engine Sn 20N3/128096 with the points behind the barrel and Tacho drive on the timing chest cover.

The problem is there was no cam thrust washer in the bits and pieces so I had to buy one. However when the steel thrust washer (3.4mm thick)is fitted to the cam the crankcases won't go together, cam was properly engaged on the timed breather lugs.
With the washer removed end float is 1.2mm.

The R/H crankcase has a flanged top hat bush fitted, the L/H has a plain unflanged version, crankcases have same serial numbers so are matched. I did find a shim in among the bits that fitted over the cam and between the drive sprocket and crankcase which brought the end float to 0.54mm.

Question is does the thrust washer normally need to be machined to size or is the set up I have with no thrust washer inside correct for this year of engine?

Any genuine experienced idea's would be really appreciated.

Cheers

Mac.
 

L.A.B.

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willy mac said:
Building an early 750 engine Sn 20N3/128096 with the points behind the barrel and Tacho drive on the timing chest cover.

The problem is there was no cam thrust washer in the bits and pieces..............

......is the set up I have with no thrust washer inside correct for this year of engine?
Yes, the 20M3 engine/camshaft doesn't have the thrust washer as it has a flange/shoulder on the camshaft.

https://andover-norton.co.uk/en/shop-de ... o-nm22729-


The hardened steel thrust washer is for the later camshaft as it prevents the tach drive worm gear from cutting into the bush.

https://andover-norton.co.uk/en/shop-de ... r-06-2608-
 

Ron L

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splatt said:
As the factory doesn't/didn't list different size thrust washers I wonder if they worried about it,which way does the tach drive push the cam?
sorry misunderstood were the clearance is, pinion holes not damaged causing misalingment ?
Not exactly true. For 1972 crankcases, the scrolled cams required a thick, beveled thrust washer (06-1086), while non-scrolled camshafts require two thinner thrust washers (06-2601) which have locating tabs. Most builders remove the tab to prevent it breaking and falling into the crankcase.

So the cam used as well as the bushing will affect the free play. Fred Eaton (Old Britts) has a very informative article on cam bushings and camshafts.
 
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Ron L said:
Not exactly true. For 1972 crankcases, the scrolled cams required a thick, beveled thrust washer (06-1086), while non-scrolled camshafts require two thinner thrust washers (06-2601) which have locating tabs. Most builders remove the tab to prevent it breaking and falling into the crankcase.

So the cam used as well as the bushing will affect the free play. Fred Eaton (Old Britts) has a very informative article on cam bushings and camshafts.
Ron
I wonder if people can get the wrong impression?
while non-scrolled camshafts something different to follow.....?

ALL 20M3S and after get a 06-1086 beveled steel washer.... ALL Cam style makes NO difference....ALL bushing style makes no difference

ONLY the OEM 72-73 750 (200000+) used the stupid 06-2600 / 06-2601 bushing-washer system
This system should be removed/replaced and or at a minimum modified to remove the killer break off tabs.

this following paragraph from ol brits is VERY MISLEADING because again ALL 20M3S and after get a 06-1086 beveled steel washer

06-1086 -- NORTON, Washer, Thrust, Camshaft, 1971 On ( $8.45 each). This thrust washer can be used with any scrolled cam in any crank case with the tachometer drive in the timing side crank case. If you substitute two 06-5428 bushings for the one 06-2600 bushing as described above, use this thrust washer.

again: ALL 20M3S and after get a 06-1086 beveled steel washer...ALL.....Cam style makes NO difference.... bushing style makes no difference
 
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Check cam lobe alignment with the lifters (install one case 1/2). If things are too sloppy and you shim it the wrong direction you could have interference.
 
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