I cheated this time... instead of buying the kit, I sourced an already built MS381 from a FarmerTec distributor. Didn't build it myself, but wanted to give it a shot. And hey, if it blows up, I'll be back on here with a teardown and failure analysis. For now, I've got 4 tanks of fuel through it, without too many complaints.
HOWEVER, there are some complaints. Right out of the box the carb was not adjusted well at all. Took care of that and put her in a log. Seems like the clutch slips, anything more than the weight of the saw stops the chain. I am chalking this up to the rings not being seated yet, as it must not be producing full power. Others have said this is an 038 Mag basically, which would keep right up with an 044. Mine does not. The 044 I used to use would cut circles around this thing. I am again assuming it's just not broken in yet and I'm trying to be patient with it.
No matter what I do, the air filter will not seal. Every time I refuel, I remove the air filter and clean the saw dust out of the carb throat. I don't like that, but have read on here that the OEM filter does not fit with the AM air cleaner housing. I sent a message to the seller about this, and they sent me a new air filter and a piston and cylinder kit, since I told them this would murder the engine.
They also fitted the saw with a 24" bar and chain when it was sent to me. Right away it was an issue. Sinks into a cut then stops biting, chain spins but doesn't cut. I have to rock the saw to get a bite again. I told them about it and they sent me a Stihl 20" bar and chain instead of their no name 24". So far so good with the Stihl setup. I guess they made it right, can't complain too much.
Otherwise, this is an easy starting saw, runs well now, and pulls the 20" chain as long as I don't get too aggressive. I installed oversized felling dogs but I can't really use them without stopping the chain. If it doesn't get better in a few more tanks of fuel, I may throw a clutch and drum replacement on it.