Sudden change in fuel burn

[glickle]

OK guys here is one for your great minds:
My engine has been nothing short of perfect with 500 hrs now. I installed the carb plate and noticed a minor drop in fuel burn on my EI fuel flow at 2300 rpm to 6.7 or 6.8 gph a .1 reduction ( and rock solid at these numbers for 500 hrs) and ran smoothly for a few months. Due to a battery beginning to lose its top mo jo had a hard start resulting in a compression bump/kickback, was not as bad as a a backfire and no big deal it went on to start fine. After that start however, I noticed I am burning 7.2/7.3 gph at same 2300 rpm and the engine leans a bit sooner and more dramatically based on the length of the mixture control. Led me to think an intake leak and engine runs great and very smooth. Definately a change but cannot locate source.

Have checked the following:
all intakes and all have been redone just to be sure no intake leaks
primer
Cylinder leak down perfect
K factor for the EI and double checked actual fuel burns all AOK
Carb insert solid

Next on my list making sure the RPM gauge is accurate.

ANY Ideas? Best Gary

[Clay Hammond]

Running 100LL all the time?

[glickle]

Running 100LL all the time?

Yes sure have

[carlconti]

Given all that you have done to eliminate air leaks, it seems possible that there may be a carburetor problem. The carb is basically an old fashioned automotive type float based design. Next step could be to check all external carb settings, followed by removing and checking the carb internally-float level, float valve, jets, gasket, etc.

good luck, Carl