I don’t know how best to organize this info, but want to capture some recent troubleshooting suggestions under other topics. Please feel free to add to or correct this list or start a new and better organized troubleshooting topic. My apologies to all for not giving you credit or for poorly representing your suggestions.
An ounce of prevention is worth a pound of cure. Don’t jump to conclusions or assume the worst. Keep an open mind. Make lists and diagrams. Ask for help.
Perform a baseline test regime: Run and record performance under specific, repeatable load and conditions (Wayne video records a 0-60 mph test on a specific stretch of road).
Test engine on gasoline to see if problem persists before blaming gasifier.
Change, alter or fix only one thing at a time* so you will know which action fixed the problem. Make a list and start with the easy stuff.
Air leaks–pressure test with soapy water, smoke test, create suction and watch a vacuum gauge or manometer while using liquid on suspected joints and fittings. Don’t assume stock parts (air cleaners, hoses, fans, blowers, valves, etc.) are air tight. When running on gasoline, closing air mix valve and gas pipe will stall engine immediately. If engine runs at all you have an air leak near engine.
Engine compression– stuck valve or particle holding valve open.
Gasifier Restrictions–water, tar, rodents, wasps, bends, kinks, collapsed hoses, flame arrestors or nozzle too small or glazed over with clinkers.
Engine Restrictions–Use compressed air at spark plug hole to check for restriction between cylinders and throttle. Burn out carbon in intake manifold. Use additives to remove carbon build up in cylinder and around valves Marvel mystery oil, BG’s EPR (Engine Performance Restorer) etc.
Spark plugs–keep clean and reduce gap by 20% except on new feedback ignition systems.
Timing–sheared flywheel key or cracked flywheel can cause starting and running problems.
Mixture*–If running petrol and too rich there will be smoke out the exhaust. When running on woodgas you can richen the mix enough to kill the motor and there will be no smoke.
Flare-Does your gas burn on its own? For good engine gas, it has to ignite with a spark and burn with a roar. (Some fan/blowers may push too much gas through the flare pipe or the flare burners don’t introduce enough air to sustain a good flare.)
Consult old gasifier manuals for trouble shooting tips–Pederick, etc.