200 vs 220 head gasket

[colingrigson]

My 200 cylinder is getting pretty trashed, but I managed to find a nice 220 cc jug so I decided to fit it to my KDX200.
One question that I have is about the head gasket.
The gasket kits that I have available here in NZ don't make any distinction between the 200 & the 220. They say they work for both.
Is this how it is? I can use a 200 head gasket on a 220 jug?

[Chuck78]

The only difference is the bore size, they must only stock the 220 gaskets?

You need to run a 220 head as well unless you are going to do some extensive machining work to open up the diameter of the head by removing 1.5 mm worth of material as well as using a radius tool to increase the volume of the dome so that you don't have to run race fuel. Increasing the bore size will increase the amount of air being compressed, thus increasing the compression ratio if you don't increase the chamber size of the head.

There are also slight deck height differences between the 200H and 220 which I believe originates both from the crankcase and perhaps the cylinder, the crank cases are a different part number despite looking absolutely identical and having everything physically bolting up in the same fashion.

[Chuck78]

Also, the bushings for the power valve subport drums are different heights between the 200 and 220, if you swap them one direction, they will lock up because they are too tall, and your head gasket will not seal, if you swap them the opposite direction, they will be loose and rattle around and cause excessive wear and noise that you will not be able to diagnose easily unless you are aware of this problem or swap issue.

Honestly I much prefer the smooth roll on torque of a 220 when it is tuned with the ignition timing in the middle position, but if you ride a lot of wide open terrain you will be down a couple horsepower in the upper RPM ranges versus the 200 H.

Hopefully you are not talking about a 1989-1994 KDX200E, as there would be significantly more work involved in swapping a 220 cylinder onto one of those because everything in the right side of the engine in the clutch case housing will need changed out, perhaps not the clutch basket, but the power valve governor and linkages, water pump, housing itself, etc

[billie_morini]

Chuck either confirmed what Colin already knew or saved Colin from some hard lessons. Either way, thank you, Chuck, for sharing your encyclopedic KDX knowledge.