Originally Posted by
dameetz
I m having trouble tuning my Plus 21-3 7 ports on road engine. This is a fairly new engine with less than 1 gallon on it and only seen one 45 mins race.The compression is still good. Initially the tune was good max temp was around 110C, right now i notice the performance of the engine is getting poorer in all areas, low and top end. Whenever i punch the throttle the engine would bog and later found out the reason behind it was the fuel was spiting out from the carb instead of sucking it. Then the engine would not scream as before on the straight and the temp was higher, around 130C. If i richen it up it would not engage 2nd gear and the speed is even slower than my 10th scale touring. One more thing I notice is my carb become very hot just after a few minute starting it.I m using stock head shims, 25% tornado fuel and Nova C6TGF plug. What is wrong with this engine?
Try another pipe. Fuel spitting out of the carb is a pretty sure sign that there is something in your pipe, blocking off holes and increasing back pressure (hence the fuel is blown back out of the carb.)
Had the exact same problem once and it was a piece of an silicone header gasket which did this.