Crank end float

[brufsup]

Hello, I seem to have quite a lot of end float on my crank. It's a two bearing case and has a Phoenix crank. I can't find anywhere how much the end float should be.

[Chris KC]

Assuming you have a standard bearing set-up, the shaft is located axially in the casing by the two front main bearings, which should be assembled with a pre-load of 0.002 - 0.008".

If there is enough end float to notice, the first thing which comes to mind is that the front bearing retaining lip in the crankcase may have failed? Stop running and investigate.

[brufsup]

The engine is stripped, just the crank and camshaft still in the case. The front bearing lip has had the normal repair plate repair and looks well done. How can you reduce the crank end float though ?

[Bob Culver]

Or the repair cover plate is machined wrong or a crankcase and bearing combo needing spacers has been adopted without the spacers. The front cover should be slightly proud. Not impossible that the cover loose, or crank dog loose! Not sure that float within the limits of a very worn race much matters in itself. vertical movement makes the rumble.

[Tony Press]

Being a Phoenix it is unlikely to have the ball and roller bearing at the front , so check the two angular contact ball bearings for correct assembly back to back or damage/wear. Also check if the angular contact bearings are the narrow outer ring type in a deep front housing.

[brufsup]

Here's a photo of the front bearing retaining plate. There's about 1mm end float on the crank.

[Chris KC]

There are I think 3 basic possibilities:
1 bearing outer races have end play in the casing joint.
2 shaft has end play in the inner races
3 the bearings themselves have internal slack allowing the shaft to move even though the outers are firmly clamped in hsg and inners are tight on the shaft. This might be because they are installed the wrong way round.

[Bob Culver]

Does the front cover plate stand slightly proud of the crankcase? Can the shaft be seen to move relative bearing inner rings, or do outer rings move in crankcase? Even if back to front cf customary, unless the stepped type, ac races should have little movement. (sorry KC. Somehow I jumped past your post immediately above!)

[Chris KC]

My money's on (1) above. The front bearings rely on a good axial clamp force to stop them rotating in their housing. Once started the front and rear plates will wear away quickly. That's assuming it was all assembled tight to start with.

[brufsup]

I can see the bearing outers moving within the case when I push & pull the crank to see the end float. I guess I'll get the crank out. Never done it before, but looks simple enough.