I have been checking into several different weedies and chainsaw engines lately. I find some have endplay some don't. Is endplay common for some and not others? Does it effect a conversion? How much is ok if any? I have a Poulan 46 with a good cylinder but has about .025 endplay.
Thanks!

The ones with noticable free endplay will probably be needle roller types, ball bearings will tend to hold the crank more rigidly ( when testing for free movement by hand ).
These (needle roller) types need some form of thrust bearing added to take the pull of the prop ( if it's for aircraft applications). Making ball bearing types more suitable for aircraft.
The ball bearings will also be able to move slightly, (ie. axially in their housings when the alloy crankcase warms up), to compensate for differential expansion between crank and crankcase.

There was a discussion about this on a Poulan 46 about a month ago. The problem was not the bearings themselves but was the result of the 3rd scenario mentioned above by Willdo. Keep in mind that there are a couple different kinds of bearings in the Poulans. Some have a seperate seal and some have the seal made onto the bearing.

Enjoy,

Jim