I am considering a gas flowed head, and would like to hear of any success/failures done in the UK.

Any recommended machine shops? (Flow bench set up).

Thank you...Richard

Off The Road is the only one I know off in that neck of the woods.

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My 04 XTX
Stage 1 & 2 DNA filters / Kev fuel mod / snorkel mod / Drilled air box mod / Engine breather mod / Fork Spacer mod / 15w fork oil /
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My 07 XTX
Raptor 700 cylinder 102mm / Modified Crank Case to take a 105mm Raptor Cylinder / 11:1 102mm JE Raptor piston / Stage 1 Raptor Hot Cam / Ported head / Colder Spark Plug / +2mm Throttle body / DNA stage 1 & 2 filters / Modified Air Box / Snorkel removed / Worry Brothers stage 2 filter cover / 6mm & 8mm Bolts Replaced with Titanium Bolts / Recovered seat in Black / O2 Eliminator /

My 09 XTX
59HP at the rear wheel / Stage 2 Raptor Hot Cam / DNA stage 3 Air Box / Carbon Can Exhausts / Modified Exhaust Link Pipes / PCIII With Custom Fuel Map / Wideband Commander O2 Data logger / LCD100 Dyno Jet display & fuel adjuster / 2500 OHM HT lead instead of a 10K OHM XT lead / Extra Coolant Cooler / Protaper Fat Bars / Tail Tidy With LED Tail Light / OKE Protection Knobs / LED indicators / AIS blocked / Modified rear sprocket rubbers / Rear Foot Pegs removed / 09 ECU With 02 Sensor Changed To A 06 ECU / Complete wiring harnes Changed from 09 to 04 / Home made LED resistor flasher / Hole drilled in the fuel tank filler neck to allow quicker filling / Modified Bar End Weights / Progressive front fork springs, 15W fork oil, forks lowered 25mm, used XTR rear links lowering the rear 20mm, rear spring one click stiffer / Changed front & rear guards from blue to black / 47T rear sprocket / Speedo Healer V4.0 / Kev throttle cam mod / Throttle grip mod / The new 2010 O2 sensor mod is out, works a treat, The new 2012 O2 Controller is out, PM me for details

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Kev, there are a few engineering co.'s in the UK with flow benches...I will try and avoid OTR, but thank you for your input mate.

Kev, why did you sell your head and big bore kit? You didn't like it??? I know you are probably more of the sort that likes projects, but surely that was a "keeper"?

I believe Kev had his big bore on his old XTX and sold the big bore seperately when he sold his bike.

Not to mention it also pathes the way for a 2009 XTX big bore.

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09 XT660X:

CCC Stainless Rounds, Stage 1 DNA, Stage 2 DNA, PCV With Custom Autotune Map, PCV AutoTune, Home made O2 eliminator, Self machined Fork Spacers, DIY Autotune Switch.

So, its a possibility for Daz's bike too?

I think if you're doing a big bore, you might as well flow the Head....

I would like 12:1 or under compression, not a mega bore, just 700-ish, flat top type piston if that is possible,, and keep standard valves.

I'm a long way off before I start engine mods im afraid.

Quite simply don't have the funds. I do know of a company locally to me though that can machine out the cylinder and possibly plate it so its all possible.
I have other projects I need to attend to first.

I believe a 700 system on these is a 102mm piston? So that would require a 102mm head gasket and if possible, blending of the head to the cylinder.
Thats if you stick to the standard cylinder and bore it out.

If you do like kev and fit a cylinder of a raptor 700, there are a few extra mods you need to do, including fitting a different base gasket.

I'm not sure if its possible to bore the standard 100mm to 102mm without removing to much material, remember, if you start removing material reliability would be degraded but it would make for an easier job unless you swap the liner for a 2mm larger one.

Flat top piston with this style of engine is hard to come by.
The reason a piston would have groves in it is to make room the for the valves. Some cylinder heads are designed so that the valves sit proud of the machined base of the head. Because they sit proud, they enter the top of the cylinder, only by a few MM mind when closed. As the piston rises during its Cycle, it'll come very very close to the top of the cylinder, if it was a flat top, it'd likely collide with the valves, even when closed!
With the grooves it allows for the piston to come ever closer to the valves during the compression cycle, the deeper the grooves the closer it can get increasing the compression ratio.

There are of course other factors to take into account of compression ratio such as the height of the pistion, centre of the gudgeon pin, crank height, con rod length, even the thickness of the valves.

There is a resonable amount of power that can be had from decent head work. I used to have a VW Polo, little 1.3 where the head gasket had gone and struggled to start because of water getting into the cylinder.
I removed the head, took it to work and skimmed off an unknown amount (cowboy, yeehaw!) to remove some pitting, new stem seals and relapped the valves into the seats.
No gas flow, or port and polish. Just a small skim and lapped valve seats!
After refitting the head I took the car for a drive and there was so much more go in it. It picked up speed quicker and red lined in every gear whereas before, it struggled, was like a little go-kart!

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09 XT660X:

CCC Stainless Rounds, Stage 1 DNA, Stage 2 DNA, PCV With Custom Autotune Map, PCV AutoTune, Home made O2 eliminator, Self machined Fork Spacers, DIY Autotune Switch.