looking for opinion P&P

Clean it and replace the broken kips valve. LH sub valve breakages are common on 89-94 kdx's. Keeping them clean will help. I would also replace the aluminum collar on top of the gear as they get worn and cause slop which can also contribute to premature breakages. Port and polish is not needed, although it couldn't hurt.

I used some oven cleaner to clean mine, just don't leave it on there very long!

well, you have to pull the head and jug to get everything out. It is a little time consuming, yes. You should have no problem handling it in an evening though. A proper service manual is highly recommended for getting things put back in the right order.

Oven cleaner will "eat" aluminum, yes. If left on too long it will pit the aluminum surfaces. I found that gun cleaner works pretty well on the carbon buildup and is a safer alternative to oven cleaner.

If you have a problem with the kips, it should be consitently poor performance on either the low end or top end depending on which way the valve is "stuck". A "sluggish sometimes" condition may not be kips afterall. It will not hurt to take the valves out and clean them up and check for any broken compenents though.

Always clean everything you can when you disassemble bike parts, be it engines, wheels, or linkage.
If you do not know what you are doing, do not attempt to alter the ports. Polishing is a waste of time.....
Do not use oven cleaner on aluminum parts. Emory cloth and/or small wire brushes are the best and safest for cleaning. Good luck and ride it!

Mud

I like the green scotchbrite pads you can mount on a drill..... Work like a charm on aluminum. Cleans gasket residue off great.
Also, one of gods greatest gifts to mechanics is brake parts cleaner! Cleans everything, and evaporates with no residue. Just don't spray it around open flame, or in your eyes! Oh, and don't lick anything on your bike not certified lead free. We will get the darn things taken away from us.