XL top end / K bottom end ?

[hennesse]

Can you put an XL top end on a K bottom end?

I received an email from a guy with questions about the authenticity of his VIN and belly numbers. He's got Sportster cylinders and heads on an unknown (all I've seen is photos of the numbers) bottom end. I answered his questions, but this brought up a question of my own:

Is it even possible to put an XL top end on a K bottom end? And what modifications would be required? I have no idea why anyone would want to do this, and I doubt that this is his situation, but enquiring minds want to know...

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Way back in the 1970's, I had a policeman stop me for speeding, and he got down on his knees to look at the serial number of my bike (a 1960 Panhead), so he could compare it with the serial number on the registration (it matched). Did this ever happen to anyone else?

[Model H]

Happened to me.

[EKHKHK56]

Well with enough money....you can do anything. To put an XL top end on would take some mods. First the cylinder skirt holes in cases are much smaller. The tappet block holes are cast and bored at an angle to the bore to match the tipped K valves. XLs are not. This would create misalignment of the pushrods. Cylinder base stud pattern is different. Probably more problems but these come to mind first. Now in the pre S&S days Sporty racers would use the KH 4.56" flywheels to expand their horsepower. This required machining a small step off the flywheel by pinion bearing to install. Followed with stroker pistons these would make some good power for the racers. Anyone building a basket KH or KHK should check for that lip being present. If missing a simple sleeve spacer will fix. Erik