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Jetting for lightly modified CRF150

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This may be an oddball combination, but I thought I'd throw it out here and see if anyone has any recommendations...

Here's what I've got:

'03 CRF150: internally stock, CHM pipe, 26mm carb from an XR200 with the choke removed, CRF230 snorkel on an "opened" airbox (vented side panel.) My riding is typically done between 1000 and about 2500 ft.

My current jetting: 110 main, 40 or 42 slow, stock XR200 needle currently clipped all the way up.

Here's the problem: I've got a hesitation as the throttle is opened more quickly. Not whacked open (because I know without a pumper carb that's always going to be a problem) but rolling on there's a big flat spot early in the slide's travel... I'd estimate it happens about 25 to 35% throttle. I've tried a 45 slow jet and the engine bogs (but the flat spot remains) so I'm back to the 42 or the 40: both seem to work equally well depending on the weather. The main jet seems to be spot-on because this thing rips at full throttle. Moving the needle up has helped, but not solved the problem.

So far, my feeling is I need a new needle... now the question is, which one?

If anyone has any other ideas, I'm open to suggestions.


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