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Crankshaft fitting, the easy way.

I'm sure you all do it this way, but for those that don't here is a simple guide.
Using this method saves dummy builds and hours of frustration.
I won't go over what is already in the "technical section" about where the bearings go, only to mention that if you omit the oil flinger you will have to add a spacer that thick.

First measure the width of your assembled crank using the bearing faces.
I added the oil flinger and bearing inner race to this as I think it's easier.

Install the bearings into each crankcase half.
Measure the depth from the jointing face to the bearing inner ring face.
Note these measurements and add them together.
This is the space in your assembled crankcases to fit the crank.
If the crank is wider, it won't fit without doing damage.

Below is an example I did this morning.

M20 Crank width. 67.45mm 03-08-23 With NF305 fitted 85.7mm Outer race clears big end nut.
Righthand crankcase to bearing depth. 34.52mm
Lefthand crankcase to outer bearing and spacer depth. 51.9mm
Clearance/interference. 34,52 + 51.9 = 86.42mm

As you can deduce I'm left with 0.72mm clearance.
This is not "end float" as the crank is clamped into the outer left hand main bearing.


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Re: Crankshaft fitting, the easy way.

An additional tip is to bend the 'corners' of the oil flinger plate towards the flywheel face, sufficiently so that the oil flinger plate will be stopped by the big end nut if it tries to rotate (they do sometimes)....Ian

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