93 KX250 Cyl/head on 91 base

[Hybrid]

Hey guys I have a 91 KX 250 and I have to do a rebuild the winter (new piston,rings, wrist pin bearing, maybe crank bearings and main bearing, oil seals and gaskets and a couple of new KIPS parts) and maybe a cylinder replate and hone depending on the condition when I disassemble it again (a few scratches ain't to bad as I ride trails mostly with some hills and various terrain).

Anyway there is a complete 93 cylinder and head with piston with the KIPS valves I can get in what appaers to be good shape. I like the 93+ kips cause it has few moving parts which equals less troubles. Will the 93 fit on my 91 bottom end? I know the obvious like cylinder height and bolt patter may not be the same, but the bolt pattern don't look any different from an observation stand point than that of my 91, even the reed port and exhaust port and coolant ports.

No sense to check the parts numbers either cause they will give me different numbers due to the years.

Can any one answer this? Crogg maybe?

Merry xmas btw guys!

[Crogg]

The 93 cylinder will bolt on the 91 but there are a few problems. First, the bore is smaller on the 93 cylinder which is meant for the longer stroke bottom end of the 93. So your 91 would be a 240cc 250 so to speak. Second you would have to shave 1mm off the top of the cylinder to be anywhere close to the stock compression. And third, the power valve actuator arm is too short on the 91 case and doesn't line up on the 93 cylinder. And forth, the 93 cylinder has the Boyesen intake port into the case and the 91 case does not, so that will have to be machined as well. It all can be done.....but it is a lot of work. The 93 powervalve actually has more moving parts. The 300 kits work really well on that 91 if you're looking for more power and are quite reliable! Hope this helps

[Hybrid]

Hey Crogg thanks for the info man its greatly appreciated....................talk about a wealth of knowledge

Yeah it sounds like alot of work for no gain.

Just as well for me to just freshen my cyl up with new KIPS, plating, and piston.

So this 300 big bore kit you speak of..................where and how much and what comes with it?