Hope you find someone to do it- shouldn't be hard to get a 400f not smoking- cast pistons (OE Honda), .001" to .0015" clearance, including professional honing by someone who knows what they are doing, check and replace valve guides as necessary, new rings and seals.
There is no oil consumption between 1500 mile changes on my commuter 400, after about 20k miles (surprises me a bit to be honest).
Now, if you were asking about stopping head gaskets weeping after they've done 15k miles, that's a different question...