Crank end float

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Dec 5, 2005
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Hello all, in the midst of a restoration of a 74 850 Mk11 I have the engine out to paint the frame etc. Now I was not going to touch the bottom end, prefering to give it a try and see how it performs, type of strategy.
The engine was fired up before stripping the bike and ran very nicely, very quiet mechanicaly no bottom end growl or knocking on blipping etc.
However I have put a dial guage on the drive side of the crank and get an endfloat reading of 20 thou. I note the manual states 5~15 thou.
What do you guys think?
1/ Is this fairly typical.
2/ Not worth worrying about
3/ Never bothered to measure this dimension

As far as I can see the only way to minimise endfloat would be to add an extra shim to the outer ring of the main bearing, as shown in the parts book. I could not see much mention in the workshop manual.
Or would the extra end float be due to excess wear in the mains themselves.
Bike has 14000 miles showing, and is on standard bores with little wear showing.

I cannot see the spocket or any external device effecting the end float, is this correct?

Cheers in advance

Richard S
 

Ron L

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Richard,
Can't say it's typical for an 850, but I have seen a few 750's with roller/ball bearing bottom ends with this much end play. I would not split the cases just to shim it. If there were other reasons to split the cases, I would do it then. Wouldn't recommend it for a race bike tho.
 
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End float, still not sure

Hi Ron, thanx for the reply.

Well I don't intend racing, unless you count dragging my mates off from the traffic lights occasionally?
The 750's with the ball races would have their endfloat controlled by the ball race, wouldn't they. I figured that was why most Triumph engines have a ball race on one side and the roller on the other?
But with the Norton, on single lip outer ring rollers, both sides, the end would be determined by the fitted clearance? Ron, this is how I interpret it, am I on the right track?
So with a bike with relatively low miles, is it feasible to assume that is how it came out of the factory, so others could be runing this type of clearance. And what is the extra clearance detrimental to?
I would suspect, from my Triumph Trident involvements, that the triplex primary chain is less than happy with excessive side missalignment?
And is the end float a potential worry for the rods?

I have the engine separated and will take the barrel off to repaint so if a strip is advisable, I guess I could replace the NJ306E's and slip in some new big end slippers and clean the sludge trap.
 

Ron L

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Richard,
Your likely to get a lot of varying opinions on this one. Excessive end float will definitely have some effect on the alignment of the rods. The question that begs answering is how much is acceptable. Norton goes on record with their 5-15 thousands, but I suspect as you mention that yours and others came from the factory a bit wide. Your dilemma is whether you want to split the cases now and rebuild it with the proper shims, or wait. It comes down to what will give you the most peace of mind. Being conservative, I usually opt to split the cases and replace what I see is needed while I have the bottom end out of the frame and the barrels off.

Since the shims only come in .003 inch, you would need two to get it back to spec. I'm curious if there are any in there now. An alternative is to find a supplier for old air-cooled VW crank shims. These are available from .0095 inch.

A racing buddy of mine is using a Steve Maney 750 crank in a set of 850 MkIII cases with sleeved down 850 cylinders. To fit this crank into the late cases with superblend bearings took something like .0125 inch to bring it in spec.

You are correct that the ball bearing race controls endfloat and this is one reason that some experts prefer the ball bearing on one side and a roller on the other.
 

L.A.B.

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For what it's worth, the crank permissible end float figures quoted in the factory manual for the 850 MkIII is: 0.010"/0.024".
 

Ron L

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Thanks L.A.B.! I never bothered to look at the MkIII specs. Probably why my buddies race bike took such a large shim.

I wonder why they opened up the specs??
 
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End float & peace of mind

Thanx to Ron, LAB and Dyno Dave.
From your collective posts I feel the end float is not an issue.
As Dave made comment the oil pump gear will pull the crank to the right anyway, and then LAB's finding the Mk111's have a more relaxed tolerance, the Mk11 & 111 share common components in this area, I assume?

I did up a square case Ducati 860, that was fun in this area, to get the end float correct, however the crank was actually suposed to operate in a slight pre-load with angular contact bearings, I suppose the old Norton arrangement is slightly less sophisticated, and tolerant of a little slop here and there.

Here's a question for the educated, what endfloat force if any should we expect the primary chain to exert on the mainshaft, will it also thrust the shaft to the right and work in unison with the oil pump. Will this force alter on acel/decel modes?

Love a good decussion, and curious as usual!

Richard
 
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Richard,
If you do opt to shim the bearing I have been led to believe from conversations with various norton gurus and from my own experience with having ordered crank shims which seem the wrong size for the bearing outer application, that the exploded diagram in the parts book is incorrect and that the shim actually goes behind the bearing inner on the crankshaft rather than behind the bearing outer on the crankcase as shown in every exploded diagram I have seen. This makes sense as to get the outer bearing-race in or out you have to heat the crankcase which can overheat the bearing which is not desirable. The problem is that the inner bearing race is rather a tight fit on the crank and awkward to get on and off and I understand that the guys who build a lot of these engines have a spare inner race that has had the inside ground to a sliding fit on the crank so that they can adjust the clearance with this 'workshop' bearing inner and then fit the new inner on the crank once they have shimmed the crank satisfactorily.

excess end-float can cause problems with primary chain alignment. This is less critical if you have a belt drive primary setup.

Good luck
 
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Dave M's right. The Norvil part goes between the drive-side of the crank and the bearing inner race.

If you're going to split your cases - and I agree others here that I wouldn't do it just to resolve out of spec end-float - I'd cut my own out of shim stock and place it between the bearing and the case.

(Actually, that's exactly how I did it. Lemme tell ya, cuttin' a doughnut outta shimstock is fun, fun, fun. Just like makin' paper snowflakes... 'cept for the bleeding, cussing, etc.)
 
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Sorry to dissapoint you, I had the same situation on mine. & was told by ex norton development man that it is vital to get end float right as the banging about will knock the end out of the crankcase. I started off with about 20 thou, but got it to about 6 thou
 
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