Look at the holes, the radius by the top. It looks like there is a difference in cam tower opening. That difference is actually measurable on the screen being a couple mm on my computer screen, which would be larger on actual cylinders. Of course if the stud holes line up, which it appears they do, the cylinder could be modified if needed, with some JB Weld or TIG work and some surface filing and stoning to make flat again.

The real stopper is the location of the slider spring setup. That would likely require TIGing up the hole and redrill/retap to get it positioned correctly. Unless the slider for the YF would fit in place of the KLX slider. Their slider might solve the worst issue if it can fit in place of the KLX slider. If one could be had, that would be a cheap way to see if the project is possible. Use their center spring loaded tension set up.

 

The seller's response to this question isn't confidence inspiring.

 

In my opinion I doubt the spring does much, but I've never seen and squeezed one. If it squeezes fairly easily by hand it has little effect.

I am not sure with that pin on the slider, that it might possibly provide a bit of side to side stability. But again I'm not looking in the engine so I cannot say.

I see the slider has some raised edges to guide the chain a bit. I'm thinking it is possible that center spring could be left out if there is something keeping the slider centered up.

I did some looking, here is the current KX250F no mid spring, with adjuster near the top, same with taller KX450F, nothing really holding to center but the bottom pin:



There is one possibility that would work.

If that cap bolt is thick enough it could be drilled and a thru bolt/lock nut could be installed and lightly adjusted just off the slider, backed out a few turns in the event it needs to limit the travel of the slider under decel. Essentially a second chain adjuster. That would actually work. That slider is working as a sort of cush drive and there would still be some flexibility remaining to cushion cam drive decel.

More I think about it, I'm not sure I actually trust the various casting/forging processes of an unknown Chinese, or wherever, manufacturer.

If a KLX300 parts bike can be had, buy it. rework the cylinder and sell off bike parts to pay for whatever it takes.

 

That same cyl is listed on ebay too.

Air Cylinder Block Piston Ring Head Gasket Kit for Kawasaki KLX300 97 08 78mm | eBay

 

In the end, the kit shown in this thread was the wrong kit. The AHL kit needed is the 299cc kit, not the 292cc kit. The 299cc kit works after about 4mm is cut off the cylinder mounted lower spring cam chain tensioner. The cylinder isn't machined to allow the full length spring holder to thread in completely. From there the AHL 299cc kit is a bolt on.