Well... After browsing a bunch of 220B/220SR heads on
http://auctions.yahoo.co.jp, I used
http://buyee.jp to buy a $53.24 KDX220SR head after noticing that the squish band clearance height on the SR heads is much tighter than the US 220R (220A-4+) models, as well as of course the squish band width being wider, not to mention the dome cc volume may likely be smaller on this - yielding higher compression ratio as well as more torque and throttle response.
I almost went for a head that was externally corroded and dirty - for only $14, but after seeing in all the auctions that the squish clearance was tighter on the SR, & seeing the video from KDXdazz, I decided to go for a nice clean one for the average yahoo.co.jp auction price of low-$50 range...
Now, the suspense! They advertise "buy multiple items and save considerably on shipping!" - but how much additional is this going to run in service fees + shipping to buyee's warehouse in Japan + shipping to the USA...?
Hopefully it'll be in the $60 range for $110 total on this experiment, as that's about the cheapest 220R head in the USA on eBay at the moment.
If it's quite affordable, I'll snatch up the cosmetically corroded one as well perhaps! I think the service fees may be $80 though minimum? We'll see.
Heck, the 220SR heads look to be a better basis to machine into the RB profile than the standard 220R heads, as they don't need milled as much, nor as much taken out of the chamber - leaving a thicker casting which will promote better heat transfer....
I think that plus some porting cleanup and some very basic port alterations might work extremely well with the Pro Circuit pipe snd 90 Octane (USA ratings) non ethanol or a little toluene or VP Octane Booster added.
The 220R head is probably best for a modified 200 big bore cylinder as the best KDX configuration as far as my knowledge so far leads me to believe (from veteran pro porting gurus) is to not mill the head much at all but rather shave the base of the cylinder about the same amount (just a few hairs) to lower the transfer port height as it's a bit unconventional. This toghtens up the squish clearance so the 220R head on a 69mm overbored 200 cylinder won't need much heas work at all to perform amazingly. RB heads have only slightly different squish band width vs stock 220 heads, but a nice crisp transition to the dome which is preferred, and most importantly a tighter piston to head squish clearance.
If not turning down the cylinder base slightly, the SR head is a no brainer as it'd be a lot thicker / more metal mass left for heat transfer. The factory 220 cylinders may or may not be as good of a candidate to turn down the base, as ALL the ports are already lower, but I'll have to see what Ted Boyko says when I ship him off a 220 cylinder at some point soon. He's done some incredible work on my friend Sebastien's 200 cylinder including extensive porting & turning down the cylinder base gasket surface to lower the transfer ports as well as all the ports, and only slight head work, making more power than most 250 2-strokes now with Pro Circuit Platinum 2 pipe, Lectron Billetron Pro Series carb, & aftermarket reeds...
The 220SR head will surely be a torquey addition, but I think with the Pro Circuit Platinum 2 pipe, it will really deliver. I'll probably get 2 or even 3 if I can dig up more good deals, as they'll lend well to making something closer to an RB head but with less machining and as I said, more metal left on the head casting...or I may just find they're awesome as stock with the Pro Circuit Platinum 2 pipe and Lectron Billetron Pro Series + Boyesen RAD Valve...
After the items have arrived to their warehouse, you can apply for "package consolidation" to save on shipping by packaging as one shipment... I think a couple KDX heads could be bundled into the box with the swingarm without incurring much more package size and weight, may as well!
https://buyee.jp/help/yahoo/guide/consolidate/flow
