you would probably be ok. the porting will actualkly reduce your static compression, which is of course offset by the head work. however to be sure run a compression test with a good tester and make sure your cranking PSI is under 160-165.
take the cages out of the intakes. remove the reeed petals from the cages, then flip them over and reinstall. that should help your reeds problems until you get some new ones. unless they have already been flipped before.
you may need to remove the clutch basket. should take 1.5 - 2 hours. and the parts are the one described, yamabond 4, a new clutch cover gasket, some new oil, and some new antifreeze.
im thinking primary drive is made by a big name. some one needs to find out. they sprockets are greatr for what you pay for them, and if the chains are the same, someone else is making it.
you can weld that aluminum but its hard and takes a very skilled TIG welder. the reason being, its shit. thats cast aluminum pot metal thats chock full of impuritites, hence the funky color.