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A few questions I should have searched for!

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Actually, I did do a search on the head but got tired of reading and figured I would chance getting crucified.

What differences if any are there in the 99 thru 12 cylinder head, I'm looking to have a spare and have RB design work it over. Second I know a few of you have had the 265 kit and I'm thinking this maybe just the ticket for me in the tight woods with the wide ratio tranny. I know the 295 is all the rage right now but in my advanced age I think just a little more than stock would work better. For those that did go this route what are your overall opinions, I realize it has to do with requested porting and my druthers would probably be the mo betta massage.

Fire away!!! TIA

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Don't be afraid to be crucified here. There are only a select few here who look to belittle a question be it dumb or not. Look past those guys. They think they know it all and LOVE to make us, who simply look for answers, look like idiots. I will not mention any names but I too have been a target of those same idiots who you are likely referring to. As far as your question goes, I do not know the answer as far as the years interchangeability goes, but, I would not worry about looking for a spare for the RB designs head. I would just get it done and not look back. I was in the same boat as you at one point. RCannon, our good friend here and a 2006 yz250 owner, did get a spare head and basically later said that it was not necessary to get a spare. I can't remember if his comment was a PM or on open forum but that's what I got out of it. I trusted him and was good advice. He upgraded to a big bore and never looked back.

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All the heads will work, but there seem to be two versions (low compression vs high compression).

High compression heads (like the 2006 USA model) are more sensitive to low quality fuel in stock form.

1999-2002 Low compression head

2003-2010 High compression head (USA models)

2011-2012 Low compression head

Any head from 1999-2012 should work as a donor for the head mods. They re-cut the entire chamber to their specs.

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No big changes, they are all bored 66.4 mm and stroked 72.0 mm, except that the 2003 and up YZ250's, specifically the US variant, have a slightly lesser head volume difference of 0.5 cc, the reason why the higher compression ratio than the Euro-, Aussie-, and Japan-model YZ250's.

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There is not a lot of difference between the two. As I recall it was 1/2 cc volume difference. Meaningless when sending into RB since he'll use his specs anyway.

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Thanks gentlemen, I'm also hoping some of the 265 guys will chime in on the second question. If I were to go with the 265, will the power valve have to be massaged? I have a couple of spare cylinders without the PV in them that I picked up a couple of years ago. If the PV does not need to be touched then I can just send in the cylinder, if it does need modifiying - then I guess I wll have to keep an eye out for that.

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Hey dirtbag, I too am gonna send a head out to RB for squish mods, soon as I take time to get a spare and do the measurements.

I ordered a #8 slide on here as many have done and found that I just couldn't get the jetting right. Glad I ordered it new and didn't just get my #7 cut and still had it to put back in. Who knows, maybe when I get the squish correct the #8 will work for me. I'd say get a spare head, just in case so you always have your stock one to put back in should you need to. I like having that safety net.

If these guys knew your extensive time and experience on the YZ250 platform they'd all be asking you a lot of questions :smirk:

...

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#9; thanks for the kind words, although there are plenty on here with much more knowledge regarding what works with what piece and I'm happy to glean from that knowledge base. About the only thing that is a perk at my age is the young fellows now help me out on the trail, plus they relieve me of the chainsaw carrying burden. One thing about celebrating the 10th anniversary of my 7th birthday this year is a free skiing pass and the fact that I can use it during the week and not have to put up with the lines!!!!!!!!

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