9.9 backfiring! Reed valves?

[Rodman738]

I have a 76 johnson 9.9. It runs great at at at higher rpm. When you go slow to a idle it tends to backfire and stall sometimes.
I have tried new points ,condensers,plugs,different coils,have tried different carburetors. Tried another armature but still have same results. My compression is 115 in each cylinder. I'm wondering if reed valves could be the problem? Any advice would be appreciated!

 

[KG ON]

It will spit fuel out the front of the carb when it's running if it has a reed problem, I doubt that's your issue. Set the mixture as follows. Turn mixture screw in until it seats but dont force it further, turn out 1.5 turns, start engine and turn the mixture in until the engine coughs, back out 1/8 to a 1/4 turn lowering the idle as you can to fine adjust. Make sure the cam followed on top of the carb is engaging the line on the starter plate as the carb butterfly is starting to open.

 

[Rodman738]

Thanks KG ON definitely made a big difference! Backfire stopped for sure. Working now to keep it idling without stalling!
Do you need to remove the lead caps on these carburetors to clean for better idling? Ive noticed there are 3 areas that can be removed. Thanks for your help greatly appreciated!!

 

[oldboat1]

Do not remove the lead plugs.

Play with the idle mix a little more to get the lowest idle -- also has to go into gear without stalling. You also have a throttle idle speed adjustment on the side of the engine, as shown in your picture. Some use it to set and return to a trolling speed.

Idle mix adjustments are small (1/8 turn). You may find you need a leaner setting for lower idling (clockwise) -- may seem counterintuitive. Allow the engine to adjust between changes. If it lean sneezes as before, or stalls going into gear, it's too lean -- turn slightly counterclockwise.

 

[Rodman738]

Thanks Oldboat 1 will work on my idle mix adjustments! Thanks for advice!