Now that I look at it, my new Wossner piston was slightly dished whereas my stock piston was mostly flat. I would guess that it was done to slightly lower the CR, I bet it is close to stock or slightly higher, havnt done the math.

I am still curious why you got a JE piston instead of a Wossner.... Was your piston dished slightly? I also only had 2 valve reliefs for the exhaust only.

 

I am not sure why a JE also ,but I am very familiar with them so i was cool with it.

I believe if I remember correctly the JE is dished 1.88mm with 4 valve reliefs.
I was doing some guesstimate math and figured the 11mm overbore increases the compression almost two points. 1.88 of piston dish dropped it to around mid 12's. Now I didn't factor in the reliefs as none of this is exactly accurate but it was looking like 12:1.

 

Can you look at this pic and tell me if the dish looks similar to yours? Wish I had measured it but too late now, I would guess it is around 1-2mm but let me know what you think

 

Yes. Looks very similar. Did you get a spec sheet with the piston?

 

I'll check again but I dont think so, just the box that said Wossner / USA KLX300R, Rings 830XDS-3, Diameter 82.94mm, Pin: WP090, Clip: CW17, Clearance: .06mm

 

You may not have. I don't think I got one when I did the top end on my YZ250.

 

I can add to the 330 knowledge base, my mpg using 144/1Nwas 50mpg in the first tank, increasing to 52mpg after 100 miles, and this was me doing WOT pulls and loading the rings almost 100% of the time, doing wheelies and touching the rev limiter after 100 Miles.

I have confidence it would increase greatly if not driven like a jackass, since I was getting about 60mpg with my 250 I am happy with the reduction in mpg vs performance, even if I did lose 10mpg it's worth it for this bike now....

 

I installed a KLX300R cylinder last Fall but reading this thread is making me want a KK330 kit. I'm also partial to a plated setup.

 

One thing I noticed on KK's site is the pricing bumps way up for KLX250S, but only for that model. The KLX300 kit is almost half price (I am running a KLX300 cylinder on my 250S bottom end).

KX 250F 2004 280cc $409.00
KLX 250S 2006-2015 330cc $899.00
KLX 300 1997-2004 330cc $469.00
KLX 400 2003-2004 440cc $450.00
KLX 400 2003-2004 453cc $509.00
KX 450F 2006 470cc $499.00

Why is he charging twice the price for KLX250 when the KLX300 is the same basic engine?

 

It's more $ because he starts with a brand new kaw. 300 cylinder. You can not bore a 250 to 83mm. If you have a 300 cylinder you can send it in to become a 330.

I have never been on a 300 but I can tell you the 330 is awesome! I say do it! 292cc to 330 can only be better.