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Rotax jetting

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I have a modified 505 Rotax installed in an ATK frame, used for both street and dirt riding. The engine is a race unit from dirttrack, with a fully ported head (45 mm), big valves, a 675 cam and an 11:1 piston. The exhaust is free flowing to an FMF Q4 muffler.

The 44 mm Mikuni round-slide jets ok from idle to half-throttle, then bogs (too rich) badly until three-quarter throttle, then pulls hard on the main. It will run on top with a larger main, but it makes it too rich for mid-range running.

Current jetting:

220 main

40 pilot

XO needle jet

7DH5 needle (top clip)

I`ve tried leaner and richer mains, and leaner and richer needle jets and jets, although I only have a few needles and needle jets to play with.

What needle would work better at half-throttle in the XO jet....,

Thanks for any help on this.

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