i had a similar thing happen 3 weeks ago 2 bent valves and a stuffed guide, was going to sell it, had a beer or two, then i looked at a bike importer breakers on ebay and got a really good complete head even the valve tops had no wear, no doubt the bike would have come to the UK from the USA, so i cleaned and stripped it, lapped in the valves new stem seals, assembled it all, gave it a cold compression test 150psi on both cylinders, back in the bike started 2nd kick, this weekend i took her out for a run and it run lovely, in fact the best it has ever run, so maybe yours is worth the work.