If the bike is worth saving, I would take it to a welding shop that does aluminum to get the hole filled and retapped. A decent shop won't charge very much for that little bit of work.
However, "very much" is a relative term and depends on whether or not the bike is worth it. It will be at least a couple of hundred dollars to repair right.
Parted out minus the munched head mine only brought $450 on eBay including a Clarke tank, Supertrapp exhaust, rejetted carb and clean title for the frame. So there isn't much to be made parting them out and it is a headache with all the losers on eBay.
But check around and find out which welding shops work with aluminum motors before getting it done. I have had both outboards and motorcycles repaired with similar problems.
And I have had both good and bad work returned. But all were useable. One of the advantages of aluminum is that it is relatively easy to repair. But you want a shop that will grind it back like it was and tap the hole in the right place.
525EXC, 640 Enduro, XT200
Grreatdog screwed with this post 09-01-2008 at 05:49 PM