thanks for the advise mownie. I initially was hoping I would not have to pull the heads or tear down more than necessary, but after your response I thought about it and decided that as the 425 is such a good machine that it is worthy of the extra work to be assured that it is adequate for another long duration. I'm sure that after 1700 hrs on a gasoline engine it would probably have some wear on it. The outside of the engine looks very good, not very dirty and no oily spots. Since this is the first Kawasaki I have worked on and going by its looks I am assuming that these Kawasaki engines must be good and well designed. I hope there is some of you Deere/Kawasaki experienced mechanics that have gone through the 20hp Kawasaki engines will look at this thread and give me some more well needed advise on what is the normal wear patterns of this model engine. I will follow your advise and see what the top of the pistons and cylinder walls look like and lap the valves. With no more trouble than it would be I think it would be a good idea to go ahead and install new rings as well. Do you put a new cross-hatch on the cylinder walls when installing new rings on these small engines? Does anyone know a site where I can get the specs on the Kawasaki 20hp water cooled engine?
Again I thank for your kindness and advise
Stan

Say I just ran into the same issue broke cam gear on my 425 JD, where can I find a manual how to change it out , anyone know, got the water pump off not sure where to go from there all the case bolts are out except motor mount, do i need to replace the seal over the crank?

gimmodog/Bluehoese54,
Same problem with a JD 425 bought last weekend. Appears to have jumped time while unloading off trailer. Pulled valve covers and no movement with lifters when engine turning over. Either of you find information to your above questions? Appreciate any help.
robb1234

I'm in the process of doing the same thing - rebuilding a Kawasaki FD620. I've torn it down and replaced the pistons, rings and various other parts, but I need help in deciding to rebuild the heads. The compression was really low before the tear down (no check, just low power and a lot of smoke, blue, not white) so there was oil getting past the pistons. The tops of the pistons were burnt, as were the bottoms of the heads.

Any advice on a head rebuild?

***" I've torn it down and replaced the pistons, rings and various other parts, but I need help in deciding to rebuild the heads."***
Really? You need help deciding?
If it was me, and I already had that much invested in the outcome, of course I would be doing the heads as well.
At least I would clean them (valves out) up and check the condition of the valve seats and valve margins......and replace the valve stem seals.
That's my humble opinion.

A broken motor mount caused me bearing problems ruined fly wheel and charging coil how do I replace the new rear bering. I think it's inside the housing

. this is not for every one please be careful !!!!
At 1700 hours I would go and do everything u can to the 620 I just ripped one down at 1400 hours and my ring gap was .024 and that's way to big , should be around .012 (2.992 bore times 40)and yes put a cross hatch in the cylinders always . I went over board on my 620 I ported and polish the heads and I remove all the ruff casting inside the block and polish it i also over drilled all the oil returns to the sump I don't advise this to every one I also replaced the rods pistons and rings making sure the play in the cylinder between the pistons and cylinders was at min ,My cylinders' were dam near to specs they were 2 .993 new ring gap was .013 after cross hatch i replaced all the oil pump parts and the gov i mean why hafe a** ,might add I have also polished the out side of the engine so I got a lot of time in it but I checked everything !!! also I found the front sump was clogged from burn oil so check that area behind the rear seal . U will need a few tools if u want this right such as checking cylinder bore good bore hone and so on Kawasaki claims to replace pistons when the play is close to .030 ( which to me is to much play ) if u don't want to bore your engine but the ring gap is to big you can buy .020 rings and a ring grinder and grind the ring gaps checking the gap offten be careful and always place the ring with top up on your grinder . Good luck on start up!!! P S I notice on the heads the oil return was up high on the return so I smooth out the area around the return port and redrilled the passage you really do not need all the oil just sitting in the head !!!!!!!!!!!