Some more tinkering today. My 9.8 is running the best now, since I acquired it. Yet it still wants a raw squirt of gas when stone cold, to initial start. Researching some more. I’m thinking maybe the part that my Merc manual calls it an “idle restriction tube” is suspect. I took a spare carb apart. Had a look at it. Basically it is a pilot jet with a long draw tube on it. Seen here:
The tiny fuel orifice entry is seen above. It could easily be plugged by modern ethanol fuel. This hole (jet) is the way fuel enters the crankcase when the carb throttle valve is closed. Good chance it’ll be plugged in my 9.8 carb. I’m going back into it now.
While I am here, I’ll share a few more of my learnings on this carb:
In this photo below the main fuel jet is circled in red. All fuel entering into the engine via the carb venturi (main jet) must pass through this fuel orifice. No fuel at all, can be allowed to enter through the threaded hole with the green arrow pointing at it. Seen in here is small a brown/red round gasket. This gasket must be in place when you re-mount the fuel bowl. If this internal small round gasket its missing, un-regulated fuel will enter the main venturi diffuser, in addition to the fuel through the main jet. The engine will be over fuel’d and run too rich. It will under-perform, cause carbon build up, and fowl spark plugs.
The tiny fuel orifice entry is seen above. It could easily be plugged by modern ethanol fuel. This hole (jet) is the way fuel enters the crankcase when the carb throttle valve is closed. Good chance it’ll be plugged in my 9.8 carb. I’m going back into it now.
While I am here, I’ll share a few more of my learnings on this carb:
In this photo below the main fuel jet is circled in red. All fuel entering into the engine via the carb venturi (main jet) must pass through this fuel orifice. No fuel at all, can be allowed to enter through the threaded hole with the green arrow pointing at it. Seen in here is small a brown/red round gasket. This gasket must be in place when you re-mount the fuel bowl. If this internal small round gasket its missing, un-regulated fuel will enter the main venturi diffuser, in addition to the fuel through the main jet. The engine will be over fuel’d and run too rich. It will under-perform, cause carbon build up, and fowl spark plugs.
