Hi Greg,
The 039, now the ms390, shares a chassis with the ms290 and ms310, all of which have the horizontally split crankcase where the upper half of the crankcase is integral to the cylinder unlike a saw of standard construction with a vertically split case and a seperate cylinder.
Cost of parts and the additional labor to repair this type engine versus the cost of the initial investment typically makes these saw models to be considered not rebuildable if a new cylinder is needed.
Sorry to be the bearer of bad news.
Russ
