KX250F cyl head '04 - '06

[basanch73]

Does anyone out there know of the difference between a '04 KX250F cyl and the '06 KX250F cyl. The part numbers for it and the piston are different on the online schematic, but I can't see any visual differences with them in my hand. The '06 piston fits in just the same and the deck height and everything else looks identical, but just don't want to put the '04 cyl on and end up screwing things up!

Thanks for any help in advance!

Brian

[basanch73]

Well, I printed off the spec sheets for both and the Bore and stroke is exactly the same for both the 04 & 06. The difference seems to be in the pistons. The 04 is flat on top with a 12.6 compression ratio and the 06 has a crown with 13.5 compression ratio. Again they look identical aside from the old 06 cyl being cracked. They even show the same piston skirt wear (fore and aft on the cyl wall). Since the bore is exactly the same, the only thing I can see to be a problem would be a different inside cyl wall coating.

I'm considering buying this '06 tonight, so any insite will be welcomed.

Thanks.

[basanch73]

Well, I answered my own question after just going for it and putting the motor together with the new crank, piston, valves, etc.

The difference between the two was nothing more than the cylinder's two holes , on the cam chain side facing you that attaches to the cyl head, have threads in them on the '06. This allows the screws to go thru the cyl head holes and then tighten into the matching holes into the cylinder. The '04 does not, but instead have the threads on the matching holes within the cyl head.

I'll post some pics in a day or two with the completed project and after a test run. If everything comes out OK, I'll have a '06 KX250F with a completely new motor from top to bottom for $2800. The best thing is that it already came with all the goodies, such as the ProCircuit TI4 complete exhaust, Eng Plugs, Suspension & clutch springs, to include ASV's, New Bridgestones, "Anodized Shark something" shifters & case saver and Renthal chain & sprocket kit.

'Til Then,

[basanch73]

Well here's the pics I promised of the carnage , as result of the original owner not installing the $2 circlip properly. Perfectly good Athena piston destroyed ! Worked out for me in getting the bike with all the new parts cheap though.



Now the finished project ,





Kicked over on the second kick and sounds just like RV's bike with the PC exhaust.

*Well the pics came out small, so you have to click on them to see the better view. My BAD!

[the_privateer]

Nice, can't beat that deal with a stick. I'm keeping an eye out for a toasted 250f I can rebuild myself.

[basanch73]

Thanks and good luck with finding a 250F to rebuild. I'd look for the '06 or newer KX with their aluminum frame and 13.5 compression piston.

Originally Posted by the_privateer

Nice, can't beat that deal with a stick. I'm keeping an eye out for a toasted 250f I can rebuild myself.