[MasterMech]

I’m running 20w50 oil and might try straight 30W

Straight 30W won't improve your situation. At operating temp, the 20W50 should be thicker than the 30W. Cold, the 20W will be somewhat thinner depending on if it's on the heavier or lighter side of the 20W spec.

What should I check next before tearing into the engine and trying to possibly hone the cylinders/rering it/cut the valve seats?

Cylinder leakdown test will tell you more about the condition of the engine internals. Compression tests overlook many variables! A leakdown will tell you if it's leaking, AND if it's bottom-end or top-end trouble. Note that a top-end leak exposed with a leakdown tester is not a likely cause of oil consumption.

Option B is cheap and it’s to pop the valve covers off and replace the valve steam seals

If the guides are worn, it won't be long until the new seals are too. But it does sound like crankcase vacuum at partial throttle or idle could be keeping it from burning oil until you put it under heavy load. If the problem is worn guides/seals, then vacuum testing the cylinder head intake ports will give you your answer. The procedure would be similar to vacuum testing a two-stroke crankcase with a blanking plate that has a nibble fitted for a vacuum line and using a handheld vacuum pump to check for leaks.

 

[MasterMech]

If I do a reseal/rering that should correct any issue that a leak down test would find wouldn’t it?

Not if the problem is due to cylinder/piston wear (out-of-round or out of spec) or if the oil consumption is due to something OTHER than ring wear. Were you planning to measure the cylinder bore and piston diameter? Re-ringing a cylinder that's out-of-round will actually increase oil consumption too. 2,800 hours on the clock - that's a very real possibility.

Plus, how will you quantify the cause and repair? A leakdown reading before and after will objectively tell you what has and has not been fixed. I realize this is just your personal machine and you are simply trying to stop oil consumption on a high-hour engine. Leakdown testers aren't super expensive ($50-$150) and sometimes can be rented for "free" at auto parts stores. Plus it bears the potential of saving you from repairing an engine that has other issues that should be addressed. At 2,800 hours, that list of potential issues isn't just 1 or 2 items.

I've had/seen commercial operators that insisted on trying to squeeze another season out of 3,000+ hour engines (that were not treated well) and paid for valve work, rings, carburetors - basically anything to avoid replacing the engine or short-block. It was never worth the gamble. If the machine is good enough to try for a couple more seasons, it's worth putting a good engine back on it.

If you're confident there's something worn in the bottom-end, and don't want to fool with the diagnostics, buy a complete gasket kit, a short-block assembly, and do the valve seat work yourself.

Kawasaki Engines 593410015 Short Block - Jacks Small Engines (DISCLAMIER: Look up the correct part number for your specific engine - this link is just to get an idea of what a short-block costs.)

If you'd rather measure the bores with telescoping gauges and micrometers (assuming you already have those tools as they cost more than a leakdown tester does) and if the bores are in-spec - I have no problem with you buying a set of rings and a gasket kit. Just don't go into that blind without knowing the pistons and their bores have minimal wear.

 

[MasterMech]

Leak down test completed on a cold engine, I would bet a warm engine would give me better results but I would like worst case scenario.

Cylinder #1 is showing a 35% leak down coming from all three places intake exhaust and oil dipstick. Oil dipstick is by far the loudest followed by exhaust and it sounds like a small leak from intake. Cylinder #2 is showing a 5% leak with no real discernible location for the leak. The spark plugs agree as #1 spark plug is pretty black with carbon and #2 looks pretty decent

The 5% on #2 is excellent, especially for an engine with 2,800 hours on it.

RE #1: sounds like "she tired". I'd be curious how your readings change on a warm engine, I've seen it go both ways depending on what the specific issues were. Were both of these readings at TDC? It's fairly typical for an engine to leak down a bit more as the piston travels down the bore (towards crankshaft), especially on an engine with significant wear. If that reading doesn't change much, you likely have a broken compression ring on #1 or a head gasket issue (if compression test readings do not change dramatically with a little oil in the cylinder then suspect head gasket or other top-end issues). If the leak rate does change notably (dry test), then cylinder bore dimensions would be something I measure for sure on teardown before throwing any parts at it. That little bit of oil in the cylinder should also help tell you how much of that leakage is past the rings, and how much is elsewhere. You mentioned that both cylinders make 150psi on a compression test (probably no issue with the head gasket then but the valve leakage should also affect the ultimate reading...). Pay attention to how fast each cylinder builds to that number. Repeat the test "wet" and note any changes both in compression and leak rate.

The leakage noted at the valves (in addition to the crankcase leakage) indicates that the seats and valve faces will need some work. I'd check the intake valve guides/stems for excessive wear before attempting to re-cut the seats and/or lap the valve faces. This is one area where you might be able to say "good enough" and throw valve seals on it along with a quick lapping for a couple-three hundred more hours of use. Def try to get both the intake and exhaust valves sealing well though. Even if the stem/guide wear won't allow that seal to last another 2,800 hours. Maybe even a set of valves if the stem wear is significant or one is cracked/burnt.