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850 crank end float

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I have been searching for details of the 850 mk3 crankshaft end float tolerance.

The Haynes manual and the clubs engine rebuild video do not give any mention of 

the process of checking this or the values (that I could find).

any ideas?

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Thanks Ian

there seems to be a lot of different views on the amount of end float.

some like a small amount while others are not bothered about it.

I started off with 20 thou so put 3 thou shims in each end to get 14 thou but then

somehow ended up with 8 thou float.(how does that work).

So I think i will remove the shims and go for the 20 thou that I started with. Thats presuming the 

wellseal does not add too much.

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If the end float is not kept within the specifications then the oil pump worm will push the 850 crankshaft sideways.......and any other Norton crankshafts converted to double roller mains. At best this gives a clicking sound like a loose pushrod end.

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Well if I go for the 20 thou that will be within the 10 - 24 thou tolerance but I would have preferred it at about 16. Is it good practice to shim just one side and what about shims in the case rather than the crank?

 

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Ideally  shims need to be between items that are fixed (to avoid wear and disintegration!) . Con rods need to be as central in the bore as possible. Given a choice I think I would put the shim on the timing side between mainbearing inner race and crank cheek. Being carefull to ensure that the shim is not in contact with any radius on shaft or cheek as that will upset your calculations. I expect the Commando boys will have all the answers .

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I found a witness mark from the crank on the driveside case, so shimmed on that side using a 10 thou shim to take 30 thou down to 20 thou endfloat.

 



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