I put a good 150kms of wet sloppy trail on my 300 yesterday. It quite happily ran at the same pace as a 250SX when up on the pipe. What I did notice was that the 250 appeared to come onto the pipe much faster and he could keep the bike singing much more. No doubt there was alot of rider skill involved as the young bloke on it was super quick through the rutted and rocky sections. Not so surprising though was when things tightened up and the ground went slick with mud the 300 seemed to hook up and track and out turn it. I'm really looking forward to converting my 300 to a 250. I've been told they are also easier to jet than the 300 (which I've put heaps of hours into). It'll also be nice to be running a minimum squish.

Nelly, where abouts are you located? I'm sure someone can point you in the right direction to get your head sorted. If you were to put your feelers out I'm pretty sure you could even arrange someone on this site to receive it and then forward to RB for mods, and then return it. Might cost a bit more and take a bit more time, but may be easier than having to source out your own person to do the work. In saying that, almost any machining shop will be able to shave the head to whatever amount you specify. Correcting the volume might be a little bit more work.

squish
 

im in the uk wales,i can get the head turned down no problem just need to find some solder and measure the gap.i think were on the right track here i have never come across this problem before my last attempt at jetting was on a kx 250 and was a challenge but ran perfect in the end but i expect compression would be higher on a motox bike,anyone scimmed the head to correct squish and cced the head for correct volume.