It wont move once you tighten the clutch nut

I did tighten the nut, should I crank on it harder?

I did notice when I was checking the inside bearing, not the front bearing, that it had a tiny bit of play. Not up and down but in and out. I'm guessing that's the issue.

The crankshaft is locked by the front bearing and should slid a tiny bit in the main bearing because expansion of the crank case. There is allway a tiny bit axial play as long it is not sideways.

Also important to pull out the crankshaft as much as you can and at the same time push the cone against the front bearing.

Thanks! thats what I did. Still a tiny bit of axial play. I've never checked that before maybe it was always like that. Just don't have another to compare it to.

You can have some tiny axial play as long as there is no radial play.

Thanks everyone, ran it and had no issues. Took it apart again and the play is because of the main bearing, seems as if there is a little (~1mm) axial movement. Seems normal.

Normally the main-bearing does not determine the axial play, the front-bearing does. Also 1mm seems like a lot to me.
What is the engine you are talking about?

Nova Rossi Flash .21 PT, 2 gallons through it.
I have no play at all in the front bearing.

Ran it a couple weeks ago (2 Qualifiers and a 20min main) no issues. Took it apart and everything looks good.

If you have no play in the front-bearing then it is impossible that you have play on the flywheel once you have mounted the flywheel and tightened the nut.
So if you have play on the main-bearing(you state ~1mm) how does the bearing feel when you rotate the inner ring?

The main bearing feels smooth when i rotate it, no grit or unusual feel. It does however have slight axial play.

I'm rebuilding it tonight again, and I'm going to make sure the flywheel is up against the cone. Also have to make sure the cone is all the way up against the front bearing.
I know what you mean, doesn't quite make sense. Maybe I need to crank down on the flywheel some more.

So the main-bearing seems good to me.

When you mount the cone, make sure you pull the crankshaft when you mount the cone(open the cone with a small screwdriver if needed), push the cone firmly to the ball-bearing. then mount the flywheel and tighten the nut.
When this is done you should have almost no play.

Anyway, if you engine is working without any problems, then I should not worry too much.

As mentioned, the crankshaft must slide through the main bearing and must have some axial play/space so it can deal with the expansion of the crank case. If the crankshaft has a tight fit betwean the bearings then the crankshaft will be locked when the crank case is heating up.

Just wanted to follow up on this thread. Engine ran fine, took it apart again after the race and no damage or signs of wear on the pin or connecting rod. Thanks for the help fellas.