I thing I have an answer. Half hour ago (in Poland is no 2:00pm
) I met one guy with motorbike and I've ask him about this problem. He told me, he had the same problem if the lever loaded valve at the gas tank is on the full-open position. I have also full open so I have to reduce gas flow I hope will be fine.
One more question. Which valve is beter to to that: at the tank or at the carb?