Running Virago One Thousand Cylinders On The 920

First, the right way: tear the engine all the way down. Gut the cases; pull the studs. Carefully mount up the empty, bolted-together cases in a mill. Come in with a cutting head and increase the spigot hole diameter from 99mm to 102mm to a depth of twenty millimeters -- not very deep. Rotate the cases longitudinally seventy five degrees and repeat. Now clean out all the debris put it all back together.

Now the wrong way: pull the top end. Carefully seal the lower end against "fallout" from the cutting of aluminum. Center the rods in the spigots, and fill the area around them with aerosol expanding foam. I'm told that rags coated in heavy grease will also work. Remove aluminum by whatever approach you deem advisable. It is possible to weld a plate to the top of an old 1000/1100 sleeve; put a square broach in the plate; knurl the lower edge; and turn the whole assembly with a ratchet and extension with the cylinder studs still in place. Carefully increase the spigots from 99mm to 102mm keeping the cuts concentric. You don't have to go very deep. Have a thousand or eleven hundred cylinder handy. Slip it in and make sure that it seats. Very little material must come out. Vacuum out any aluminum shavings. Peel out the foam and other sealers. Assemble in reverse order.

If you simply want the flat deck and a maximum bore of 96mm is okay, you can mount up the cylinders in a lathe and remove material from the lower part of the sleeve down to 99mm OD. I have had this done for a number of 920 enthusiasts. The flat deck is far less leak-prone than the stock recessed gaskets.

More to come . . .

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