Originally Posted by crobox
As I posted in the main XL600 thread a while ago, I realized at some point that I had neither the old-style cylinder head with the cross-intake valve, nor did I have the new-style intake manifold with the milled passage between the ports. I mulled this over for a while and decided that instead of paying $60 or more for a new intake manifold, I would just modify mine. I did some fancy measuring to figure out what size O-ring would work. Then on my mill, I did the following.. 1) milled a radius channel at the top to join the existing O-ring grooves, 2) milled a straight channel at the bottom to connect the bottoms of the existing O-ring grooves, 3) plunge-milled four cylindrical flat-bottomed holes and filled them with pressed-in aluminum plugs in order to block off the un-used portions of the existing O-ring grooves (so that fuel-air mixture cannot get to the "inside" of the new O-ring, at least not in any high volume, and lastly 4) milled a passage between the ports.
As much as I'm dismayed by your determination to remove the greatest hue ever applied to a set of suspension components, I will still offer you a favor. If that intake doesn't work out I have a spare one I can send you.