Crankshaft

[RodneyK]

This post is a follow up to my Main Bearings post.

I have the cases put back together and the crankshaft turns smoothly but stiffly. How freely does it have to turn in order for me to proceed? How do I determine that? How do I achieve that?

[clive]

Hard to say i have just put a bottom end together. Its smooth but difficult to turn. I am putting the difficulty to turn down to grapholine installed in all the bearing surfaces (it been reground with new bearings ). How about one of the twin afficinados answering this?

[dodger]

You should be able to grip the small ends in your hands and with a push pull motion the crank should revolve smoothly and easily. If it won't it's too tight. It won't wear in it will wear out.

[RodneyK]

Thanks Dodger and Clive. It was too tight so I dismantled it again. Welding on the drive side case seems to have shrunk the required clearances. Now I must decide whether to use my spare case which is slightly different. Please see my post on the drive side case. Also, should there be any end play at all in the crankshaft?

[g80csp11]

On a twin engine , there are a few issues that can occur .
If the journal radius is not large enough it can make the BE or center web feel tight
before the crank is assembled into the crankcase, the conrod should just fall under its own weight with light oiling on assembly and torquing to specification . Worn conrods can cause the BE to be tight . usually a sign of this is that the caps are difficult to fit and feel as if they are binding on the studs
The centre web again when torqued to spec should be able to turn freely with light oiling on assembly

Only once you have achieved this , should you assemble in the crankcase