KDX 220 case – cylinder matching and cylinder port clean-up

I definitely don’t have the knowledge or experience to do a proper port and polish (PP) job on this 220 cylinder. But I think I can get away with a casting clean-up (CC) job and do more good than harm. I’m also going to take care of some mismatches between the cases and cylinder.

First thing to address is this mismatch of the cases. With the two alignment dowels in place . . .

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and the cases bolted together, this is the extent of the mismatch. I checked my other engine and it is the same way.

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This is just the difference with the gasket in place, there will likely be more material that needs to be removed once the cylinder is bolted on.

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Now for matching the cylinder to the cases. The right case is easy to align with the cylinder because of the two alignment pins on the right case half (case half on left hand side of the picture). But there is nothing on the left case (case half on the right hand side of the picture) that will accurately position the left side of the case to the cylinder.

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Here is what I did to take care of the left side. I removed the alignment dowels from the cases . . .

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Then I bolted the cases back together. I just snugged down a couple of the case bolts so that I could still move the cases around. I aligned the cases so the cylinder mating surface was even and the rear of the cases that I ground down were even with each other. This mirrors how the cases were aligned with the dowels in place.

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Slide the head on and the alignment pins on the right case will align the cylinder properly. Then tighten down the cylinder nuts on the left side of the case:

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Now just remove the case bolts and slide the right case down and out of the way:

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This was the first of several areas I was going to clean-up:

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Now looking at the underside, there is also this area that is off:

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You can’t see it from this shot, but the case is narrower than the cylinder all along the transfer port:

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This is the extent of the mismatch:

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Rough grinding done:

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Final grinding:

Cleaned up the case and the cylinder . . .

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One other area to clean-up.

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The alignment pins on the right case take care of positioning the cylinder. With the right side cylinder nuts tightened down, not as much work to do on the rear of the case. The blue arrow shows what was removed to match the left side and the red arrow shows how much is off on the other side of the opening.

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I wasn’t exactly sure what to do about these areas. They were certainly mismatches between the case and cylinder. And they were 90 degree “steps” between the case and cylinder. My searches came up empty on what others may have done, so I compromised . . .

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I just took off the 90 degree edge and now when you run your finger over the area nothing protrudes out. I figured that was enough to make a difference but not enough to completely screw something up.

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Now on to the cylinder. All I’m looking to do is to remove the casting flaws. When you first look into the 220 cylinder, this is what you see:

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The side ports look smaller than what they really are, the shapes are inconsistent between the two sides and the edges have to be creating a lot of turbulence. Once you look from the other side of each port, you see that there is a continuous casting “ridge” that runs around the opening.

Everything the arrows are pointing to is a “ridge” of excess material:

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The other side of the “ridge:

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This is like having a 4′ wide hallway with a 2′ wide door in the middle of it. That “ridge” just bottle necks the port and interrupts the airflow.

Without changing the size of the port and just removing the “ridge”, these are the before and afters:

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The only other clean-up I did on the cylinder was to remove the casting flaws from this exhaust port:

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And I removed this step from inside the KIPS port:

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And that is the extent of my grinding work. I didn’t touch anything else so I’m really hoping that the famous 220 low end has remained the same or better and that the flat top end the 220 is also famous for has been improved.

HBR Harold Bawlzangya Racing