Originally Posted by
BAD LS1
Opposed twin... Well judging by your symptoms you listed, you guessed it, the carb needs some attention. If it all of a sudden started doing this then fuel deposits are probably at fault. Doesn't take long in this heat for fuel to go cowshit. Why premium in something with a 8.0:1 compression ratio?
Typically if it runs like shit under load, your high speed circuit is at fault... But you say it's also garbage too at idle, so sound like double whammy, reinforcing the fuel deposits theory. These engines actually spend almost all their time on the idle circuit even at full speed until sufficient load is placed on the engine allow the governor to move the throttle plate off near idle and over to fuel delivery from the main nozzle.