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Oh okay. Your post#1 indicated that you thought you had low compression on one cylinder. What made you think it had low compression and what were the actual, measured compression values?
 

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Compression testing must be done with the throttle wide open and preferable on a hot engine.

As it stands now the difference in pressure between the two cylinders is concerning. The lower compression of the front cylinder lines up with the excessive carbon found on the piston of the front cylinder. So you may need new rings or new valve guide seals, but as Kawasakian points out, you might as well do a top end job while you are in there.

You can easily check the sealing of valves by pouring some kerosene into the cylinder head ports to see if any will leak past the valves.
 

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PB is not good stuff to use for this kind of test. PB's job is to penetrate, so I am not sure this is a valid test.

The only reason I said to use Kerosene is because it is a heck of a lot safer than using gasoline, but lots of folks use gasoline. It should be done outside though. I think we used a 30 minute test. If no leaks in 30 minutes its good. You could use diesel or varsol. Both should work for you. There are lots of other ways to test as well. Google is your friend.
 

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I would take the extra half hour and do a proper liquid test first, but that's just me and my OCD nature.
I will agree that most likely the valves need work, but in my books its best to be certain.

But the next very important question is what about the rings? OP says it was burning a quart every 200 miles. If that's the case, I would think the rings and cylinder walls need a very close look. I highly doubt valve guide seals could leak so badly that the engine would consume a quart every 200 miles. Anyone have some real world data on this?
 

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Burned exhaust valves are quite typical of bikes with very low exhaust flow restriction. Kawasaki OEM exhausts are tuned for a balance between power and long engine life. Third party exhausts are more about power and sound and less about engine life.

Putting the baffles back in will help for sure.

Why not get a quote on getting the valves and rings done by your dealer and then decide if you want to tackle it yourself? This assumes the crank is good and I think there is a good chance the crank is fine, but if in doubt check it out.
 

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I like that you are tying to save this old engine but I agree with Kawasakian's concern about the piston scoring. At a minimum I would measure the piston to cylinder clearances and if out of spec I would consider going to first oversize pistons if you want a lasting repair. This assumes you have a liner that can be bored.
 

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You assume it needs crankshaft work which we don't know yet. But if it does, this engine does not use side thrust washers and the plain bearings are only $19 per set. The OP says he has lots of time on his hands. Why not let him decide? After all, he has the benefit of having the engine in front of him and all we have are photos.

If no play can be detected on a vertical pull on the conrod, I would leave the lower end alone. The other option which may be too late if oil has been discarded, is to send the oil out for analysis and if it comes back full of bearing metal, well, you have your answer and it only cost $20 to find out.
 
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