I think that the quality control on the OKO carbs isn't as good as it should be. If you want to make sure it's not a manufacturing defect, you could try ordering a keihin needle jet and see if the tolerance on yours is too loose to cause a rich condition under sudden acceleration. I chased a rich condition on my oko 30 by ordering replacement keihin jet needles until I settled on a leaner needle than the factory one. Maybe the problem wasn't the needle but the jet itself.