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Those are options, but I decided to go a slightly different route. I went ahead and setup an exchange on this adapter for the larger unit and I am going to bump up to the 32mm OKO. This will give me the spigot diameter to work with the Rotax carb boots I already have.
From previous experiences on other bikes with similar cylinder sizes I don't expect it to misbehave, but I do see the biggest issue being the port restriction on the stock head since it is only 30mm. I will test it out on the stock head, and see how it behaves. Obviously if I don't like it I will simply convert back to the Fakuni until I can get around to doing the ported cylinder head, which I can port match and blend the extra 4mm diameter of the flange with a taper.
I can always go back to the 30mm idea if the 32 doesn't work out, but it will take a lot more time and effort to try and sort that out. As I said, from my previous experience with similar cylinder sizes, the engine should respond rather well across the rev range, but until it can be put into practice it is all just speculation at this point.
Worst case scenario would be a small loss in the lower revs and a gain up top with a marginal effect on throttle response (being a bit more touchy). Given my riding style and use of the bike I personally wouldn't mind that trade off. Best case scenario, and something I have experienced in the past, would be a strong gain in the mid-range and top end. This has been evidenced on GL1000 enines, which run a 32mm carb with a 28mm venturi that step up to a 35mm down-drafts with a 32mm venturi, and especially on a 40mm carbs with a 35mm venturi. While obviously apples to oranges, the individual cylinders are similar in displacement, 2 valve heads, and have an identical powerband and rev range. So it makes me optimistic. If I end up with the same kind of powerband (useable from idle to 3000, good from 3000-4000 and strong from 4000-8000) then I will be plenty happy.
Guess I will find out.
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