hi Eddie, warmed my t35 up today, and tried as you suggested to tickle the offending o/s carb. , yes it DID seam to stop the weak symptom of 'spit back'. but then here i'm puzzeled, WHY does it only happen to the o/s carb. also changed the float bowls over, but still occurs only on the o/s when snapping open the throttle. There is deffinately no problem with fuel supply to both carbs. your theory of unleaded to slide cutteraway ratio is logical enough, but then surely it would affect BOTH carbs, would it not? am going to try a thin fibre washer between brass float jet and bowl top, hopefully to raise the fuel level ! anyway where could i get new slides for my carbs, which i beleave are the originals ?, regards george.