Kawi 25hp V-twin running rough

[WinterDeere]

Welp... ran leak tests on both cylinders, hoping this was "just" a blown head gasket, since that would be a lot easier than dealing with the damn breather. Unfortunately, both cylinders look reasonably good:

left: 17%
right: 23%

This tester shows up to 40% is "good". Not sure why right is higher than left, and Deere/Kawi don't publish a spec on this, but both are well within the green range on my gauge.

I tried testing the breather with the blow/suck test on the dipstick tube, and was able to move air thru the crankcase in both directions, which would register as a "stuck open" reed.

Despite all this, I'm still wondering if I should pull the heads before tearing the whole motor down to get to the breather reed, mostly because I'm not sure why a bad breather would cause the engine to pop and run rough, and partly because the reed replacement is such a nightmare I want to make sure I checked every other possible box first.

Procedure to remove that breather reed valve is horrible:

1. Remove engine from mower
2. Remove front engine shroud and cooling fan
3. Remove flywheel (I've already done thru here)
4. Remove intake manifold
5. Remove valve covers
6. Remove rockers
7. Remove push rods
8. Remove rear crank case cover
9. Flip engine
10. Remove cam shaft & thrust washer
11. Remove tappets (lifters)
12. Remove breather cover
13. Remove breather pipe
14. Remove reed valve body
15. Inspect/replace reed valve
16. Reverse assembly, replacing all gaskets