I've got an old (1988) 8HP Briggs & Stratton engine (195422-0751-01) on a leaf blower with some problems.
After ~10 minutes of running okay, (choke open, 1/3 to 1/2 throttle), it starts to die, almost always due to being angled in any direction on a hill. The only way to keep it from dying is to close the choke. After this period, I can try adjusting the carb mixture only to get it running another 3 minutes with 1/2 choke and 1/3 throttle. Letting it sit ~1 hr is the only guarantee it'll work for another 10 min.
What I've tried or replaced:
- Carb replaced with new from ebay. Adjusted mixture screws (per engine user manual's instructions -- 1.5 turns on main, 1 turn on idle) and readjusted for hours in order to get a mixture that lets it run for a few minutes.
- Removed fuel tank, outlet nozzle, and hose to clean and inspect. They're fine.
- Used new gas.
- Replaced gas cap.
- Inspected air filter and oiled pre-filter (per manual's instructions). They're fine.
- Tested compression. Results consistently ~137 psi.
- Changed oil.
- Seafoamed gas.
- When it's dying and I close the choke (to revive it), exhaust spits black smoke.
- When main jet is opened more than 2 turns (which the engine seems to need at the time to run), there's sometimes a few drops of fuel coming from the bottom of the carb.
What am I missing?