What could this mean?
 

The problem I am having at the moment.....not very often but every now and again is sometimes the car seems to get a little boggy and just wont move unless you really nurse the throttle and bring it back very slowly. If, while the car is still running i pop the lid open on the fuel tank for a few seconds and rev the car, it clears itself through and the car runs fine again. The engine is pretty new, all fuel lines are new and the fuel tank is new if that helps at all?? I had this problem though with the old engine, tank and pipes so that does eliminate them really. Could this be a tuning issue or something else perhaps??

Adam

RE: What could this mean?
 

Yep, it's running too rich. Lean it out 1/8th of a turn at a time, until it accelerates smoothly without bogging. Then run it away from you full throttle. You MUST still be able to see a nice trail of grey smoke, or you've leaned it too much. During the leaning process, check it every few minutes for temperature too, if you run too lean you will overheat it.