I would guess that you're used to working on older pattern saws, right? Lots of classic designs had engines that were more or less separate. Most made since the '60s put everything in one casting. In Jonsereds' case, the crankcase and AV mounts are one assy, the oil and gas tanks are another. It's a royal pain just to get the two apart, let alone tear into the case. However, it can be done if all else fails. Try the inserts first. Do the cracks get to the oil passages?
"Bar cover" and "clutch cover" are interchangable words for the thing that goes over the bar and clutch. By "part under the sprocket" I would assume you mean the clutch drum.
In a side note, why does everyone use threaded studs these day? Homelite had it all figured out years ago. T-nuts going into the gas tank. You'd have to tear the saw in two before they would come out.
