The only two issues I've been able to dig up are the head gasket issue and the chain tensioner issue. I'm installing that 300 now. Both are really non issues. Some people worry that the AHL gasket covers up the holes. It does but not enough to worry about. I would not put in a 250 OEM gasket. Doing that would leave some gasket material uncompressed within the combustion chamber. Bad idea. I did order a 2000 300klx aftermarket head gasket kit off ebay. The only issue I have with the supplied AHL gasket is its bare metal painted. The 250 Kawasaki head gasket is metal but it's rubberized on its surface.

There are two tensioners the lower tensioner people are grinding off about 4 mm. Once you get it it'll be obvious. I didn't want to grind it so I took a little tiny Dremel and plowed out a bunch of aluminum in the chain cavity. Super simple stuff. Not a problem. Kit ooks nice. I am an aircraft mechanic and I can see nothing wrong with the quality of this kit from ahl.

 

I'm ready to put it together but the rear chain guide is still attached and I'm trying to see if there's a trick to removing it. I think I'm probably just going to have to install the Piston into the cylinder with the chain guide attached to the tranny. Have you got yours apart yet?

 

EDIT: Only use a 300 gasket or the gasket in the AHL kit, You do not want any overhang of gasket material in to the cylinder.

On the other hand, the gasket overhang into the water passages.. It should be no problem. Fact is there needs to be turbulence in the coolant to mix up the flow. If the flow was smooth the coolant could become somewhat laminar which would slow coolant on the surfaces while the center area would flow on past, hindering cooling. Turbulent flow will have the mix up and aid cooling on the surfaces. The flow isn't so fast that it would be very restrictive anyway. Unless it was crazy overlap I'd leave it as is and use the gaskets.

 

Thank you, @ctbale will keep that in mind when the kit arrives. Do you possibly have images / link to a post that shows how to do this?

 

I missed the part about using a 250 gasket on a 300. I edited my earlier post about the gaskets for the point that the head gasket should not extend into the cylinder.