Power valve with 1mm over bore

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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C George
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Power valve with 1mm over bore

Post by C George »

I'm sending out my 220 cylinder to Millenium Tech for a 1 mm overbore " 70mm " and a nickasil recoat.

I'm going to check when reassembling but is there usually any need to trim the power valve plate ?
05 KDX-220R / 06 KDX-225R / Maxima 927 / Millenium Tech / Ron Black / PC , FMF / Many 220 engine mods / 40 + yrs. of riding dirt bikes 🤟🤟
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C George
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Re: Power valve with 1mm over bore

Post by C George »

Yes , I've decided to punch it out to 223cc or what others call a 225 kit.

A recoat of the stock bore 216cc cylinder would have worked also but I'll probably never wear it out so what ta heck ,,, lets gain 7 cc's
05 KDX-220R / 06 KDX-225R / Maxima 927 / Millenium Tech / Ron Black / PC , FMF / Many 220 engine mods / 40 + yrs. of riding dirt bikes 🤟🤟
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Tioli
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Power valve with 1mm over bore

Post by Tioli »

Having done similar by converting a 200 to a 220 you may also need to pay attention to what you want your rear boost port to look like.
If you leave it the way it is it may reduce the effectiveness of that port which is used to get that up and over flow happening.
As a rough guide bigger and earlier is topend and smaller later is bottom end. If you leave it as it is it will be smaller.

If you wand to touch it up I would do it before you send it off
2001 KX125 with a 1997 KDX Tioli Hp motor

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C George
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Power valve with 1mm over bore

Post by C George »

Tioli wrote:Having done similar by converting a 200 to a 220 you may also need to pay attention to what you want your rear boost port to look like.
If you leave it the way it is it may reduce the effectiveness of that port which is used to get that up and over flow happening.
As a rough guide bigger and earlier is topend and smaller later is bottom end. If you leave it as it is it will be smaller.

If you wand to touch it up I would do it before you send it off
Thanks , I'll double check that as I worked the boost port area when I did the Intake.
05 KDX-220R / 06 KDX-225R / Maxima 927 / Millenium Tech / Ron Black / PC , FMF / Many 220 engine mods / 40 + yrs. of riding dirt bikes 🤟🤟
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C George
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Power valve with 1mm over bore

Post by C George »

I did notice that the 70mm piston won't fit thru the stock head gasket. :?
05 KDX-220R / 06 KDX-225R / Maxima 927 / Millenium Tech / Ron Black / PC , FMF / Many 220 engine mods / 40 + yrs. of riding dirt bikes 🤟🤟
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