Deck the head or not?

RB-Designs does some great work for the KDX head.

The 200H has a fairly low compression ratio. You can go up a few pounds of compression and still use pump gas. You'll gain some snap off of the bottom. If you increase compression too far you'll have to go with race gas and lose some top end run out.

I had Eric mill the base of my cylinder to gain some bottom end (slightly lowered port height) as well as increase my compression. I only gained 8 lbs of compression, but am happy with the result I got.

The bottom of my cylinder was milled before I bought it, and I have found that the teeth on the KIPS actuating lever do not quite mesh with the KIPS shaft anymore, causing premature wear. And, they are not cheap to replace! Just a little something to keep in mind before you start mucking around with it...

Cheers,
Andrew

I'm not sure how much Eric milled my cylinder base, but my KIPS gear teeth seem to still mesh pretty well and I'm not noticing any wear problems.

Its a great mod with a noticable difference down low. If you like to lug your KDX like a 4 stroke in the nasty stuff or need a bit more for hill climbs, loose soil/sand ect you'll love it. No problems running on pump gas. For $35 ya can't go wrong.

David

David. Could I ask how much you are talking adout milling and if there is anything special in mind as far as squish etc.?

alright any body that has personal experience or a good knowledge of this topic on a 95 or newer kdx200. I know somebody knows so please give it up. please!

Decking the head to adjust the squish is a great mod with a very modest associated cost. I have had it done on the three KDXs that my boys own. A 96 200 a 99 200 and just two weeks ago a 05 200. A local shop did the '96 in about 97, Eric Gorr did the 99 in '00 and RB Designs did the 05 two weeks ago.

Most of the reputable shops now use TSR software to determine the amount of material to remove and the squish angle to employ and the combustion chamber size for your alitude and fuel preferences.

We ride from 5-10K feet elevation and the head mod really helps. You should be able to tell a significant difference especially if you jet your bike correctly. The head modification will be most noticable at low to mid rpms. It lugs better and dialing the jetting is easier with the throttle response being crisper.

With the 96 we shot for .045 inch squish. i.e. measured the piston height at TDC and then measured in the area of the piston dome/squish band. Measured the head gasket thickness and added it to the measured head squish band. Subtracted the .045 from the resultant number. This number was then then machined from the head. We left the chamber and orignal squish band width untouched. Bike did run noticably better on pump fuel. (I believe we removed about .022 inch from the face of the head but I could be wrong since it was quiet a few years ago.)

After software information started to be available for 2 cycle squish calculations and especially after the TSR software was endorsed by field leaders: we now look only to shops which use the software/ OR are specialized in hopping up one particular bike. Most shops recut the squish angle and resize or even reshape the combustion bowl. The simple technique of "decking the head" IMO went out the door about 5 years ago when squish software took some of the 'black magic' off the table.

Bottom Line - If your porting is stock send your head off and have the work done on it by a reputable shop. You will be surprised at what this will do for the bike. Many shops can perform the work and all they really need to know is the type of fuel you want to run and the lowest altitude you'll run. It helps them if you let them know the pipe you run.

P.S. If your porting is anything more than mildly cleaned up then I would withdraw this recommendation since too many variables are into the playfield.

FWIW - RB Designs appears to have done an outstanding job on the 05's head. Combustion bowl is polished, the squish angle is recut and the head has been 'decked'. The turn around was extremely quick, communication was excellent as was the machine work. AND the price was right!! :laugh:

Hey thanks a ton! That is exactly the kind of info i was looking for. Well it looks like that is the next mod on my list. Bottom end and mid is exactly what i'm after. I mostly put around and i weigh 225 to 235.