hello, I'm sending my cylinder head to my machinist to be surfaced so to get about .035 squish area. Obviously it will increase compression. I know a lot have done this, would I feel in the difference of power, if any when this mod is done. Any changing in jetting?
My KDX head has about 3mm of squish now.

inquiring minds what to know.

Which bike is this for? What is the stock squish area for this bike in comparison to the .035?

If head is milled... it will for sure increase you compression psi... if it gets to high could add some stress to the engine... but can easily be adjusted by adding an extra base gasket ect.

Proper timing will be needed to find the sweet spot and keep kick back to min.

Just speaking from my experience I have had doing this... for the 360's i have found 140 to 145 is where you would like to land and anything over is pushing it and need to make sure you give it plenty of fuel so none of those dreaded pinging sounds!

The Black Widow bike sits at 140 right now with an MX High Compression head and is dialed in.

Back in "87 i got my "86 KX125 taken down pretty close by memory & certainly sharpened it up. I'm sure i went up one size in the main & one notch richer on the needle just to be safe & think i left them set at that. Thing is, at the same time i would have replaced the piston & rings & new rings always sharpens the power up on a ring dinging 125 mxer. Loved that bike & funny thing 'was' the original piston lasted well & every regular change after that had elongated the small end hole in the piston & i knew because it rattled in a certain way & could grab the pin & move it vertically. I used the original piston with new rings at times if replacements were on a 'slow boat' arrival. & original never altered. Made me think replacement [genuine box] were made of cheese. Come to think--i'm sure i started using AvGas then, so power increase with more comp was really noticeable. 34 years ago--.

If done correctly, it will make a very noticeable difference.

Water cooled is much more tolerant if compression is added... good shops that know the model will machine the combustion chamber to correct the compression if needed on that model... usually isn't needed.

My maths isn't good but you say .035 so is that 35 thou getting towards one mm. Not .035mm about 14 thou. I'm guessing the first one. Sorry if i sound thick lol but can be at times.

Mr French my KDX220r is the bike i'm speaking of.
I know RB Designs and Fredette Racing along with shaving the head they configure the combustion chamber, plus they both bore and modify the carb.
I'm going the cheap route right now.
The cylinder lining was also flaking so as we speak it's being re-plated at Millennium Technologies, so that along with new piston, surfacing the head should make a fairly substantial increase in compression.
I might be heading to some desert in April to test it out.

So this is want I'm doing to maintain social distance and staying busy, I've also mowed my lawn 23 times.

The angle of the squish area needs to be changed with the machining. More important than milling the surface. Hopefully your machinest knows 2-stroke engine technology. If not send it to these guys. www.klemmvintage.com/ Here is a GYT head machined for 180 psi and a stock one for street and 91 octane gas

thanks Pillsbury,
just curious, other then taking the engine to him with cylinder and piston installed, how would you determine the angle of the squish area, pistons dome is arced.

They (klemm) require your current piston to do the mods for best performance in terms of cooling and power. But, if you can't send them the piston the work will not be as good. They are top notch in deàling with detonation issues, whether your head is listed on there or not, you'd have to call them.

KDX is a very modern engine compared to an old DT. Kawasaki knows how to make power. Angle may or may not need to be changed.

The biggest problem with excessive squish clearance is that there is a lot of mixture trapped there that gets "quenched" and doesn't burn. It's worthwhile to reduce that clearance. Factory doesn't do it because of mass production assembly tolerances.

If on a budget, reducing the clearance will make a significant difference in power... on squish angle, three experts will often have three different ideas of what is best. And you probably couldn't tell the difference between the three by seat of pants. Keeping in mind that Kawasaki engineers are experts too...

Just my opinion and experience... and we all know what opinions are worth!