thankyou for taking the time to respond.im almost 100% sure its the fuel tank foaming.the only problem i have ever had with a jett engine.is always tank related.so i pulled the tank last night and made the bubbless fit.as long as i have a good solid stream of fuel.that will make setting the needle easy.also if im seeing 18,300 with a 8.5x7.5 do you think ill see better speed with a 8.5x7.0?thanks for the help.