Keeps fouling plugs

Engine model number?

Check the crankcase oil is not contaminated with fuel.

Inspect the sparkplug. If its oil fouled (black sticky wet deposits), do a cylinder leak down test.

If plug is oil fouled, you could replace the plug and it will run but it will likely oil foul in an hour or so or even minutes... it would confirm rings are shot and the leakdown test not necessary, but be sure fuel is not getting into crankcase.

It's also possible the decompression mechanism has failed. It will start with the extra fuel from priming then die. Could also be impulse air to fuel pump... model number?

Double check air fuel mix screw settings for new carb... again model number?

Hi Abbott:
You've gotta be close. Let's double check.
- Pull the plug(s) and make sure they're not fouled and that there is a nice hor blue spark across the electrode.
- Fresh gas in the tank
- flush the carb (drain plug)
- Fuel filter if there is one.
- Clean the air filter.
Put it back together and give it a try. If it runs, great, if not, pull a spark plug and see if it is "wet" with gas. If not, the problem will probably be with gummy bad stuff in the carb. Take it off, and an air hose to try to blow out all the little passages.
Keep smiling, you'll be killing bugs in no time!

Check for spark on a plug wire when it won't start. If no spark until it cools down, the ignition system is the problem. Could be the coil, the ignition control module (igniter), a crank sensor or pick-up coil, depending on your system, ...some of the most common things to check. If it just stalls, likely lost spark or gas to the engine cylinders. With a new pump, it probably lost spark.

Could be fuel or oil fouling. Need to determine which first off. If it is black sooty fouling it is likely too rich also it too rich may be wet.

If oil fouling it is more likely to be much more material fouling and wet sticky material.

A wet, black and shiny deposit on plug base, electrodes and ceramic insulator tip indicates an oil fouled plug. The condition may be caused by one or more of the following: worn pistons, worn piston rings, worn valves, worn valve guides, worn valve seals, a weak battery or a faulty ignition system.

A dry, fluffy or sooty black deposit indicates an air/fuel mixture that is too rich, engine idling for excessive periods of time and/or enrichener usage for excessive periods of time.

A light brown, glassy deposit indicates an overheated plug. This condition may be accompanied by cracks in the insulator or by erosion of the electrodes and is caused by an air-fuel mixture that is too lean, a hot-running engine, valves not seating or improper ignition timing. The glassy deposit on the spark plug is a conductor when hot and may cause high-speed misfiring. A plug with eroded electrodes, heavy deposits or a cracked insulator must be replaced.

A plug with a white, yellow, tan or rusty brown powdery deposit indicates balanced combustion. Clean off spark plug deposits at regular intervals.

check for oil gas mixture or its bad rings

If the black deposits on the sparkplug are dry and fluffy then your problem will more than likely be a blocked or restricted airfilter. Your airfilter should be the sponge type, wash it in a soap water solution, dry it thoroughly then apply clean engine oil to the filter, squeeze it through then squeeze out the excess in a dry clean cloth. This will leave a fine residue of oil to trap any particles of dust. A heavy residue of oil in the filter will cause the problems you arte experiencing.
If the black deposits are wet and oily then either the sump is overfilled or the piston rings and cylinder are worn.

one of two things needs new plug or coil is getting hot an breaking down.i would think coil because it restarts after cooling down

I'm not an expert.. But.. What I would try first is, remove the spark plug, drop several drops oil into the cylinder, try to get it to move around piston head. Let that sit for a hour or so. Try to crank it without the spark plug. May get some oil spray, look out.. If it cranks ok, then put the spark plug back in, and try it. It's possible it may not start still, because carb/fuel is dryed out and gummed up. But first step is to loosen the piston. Good luck.

You will need to check the fuel pressure, if it is on the minimum pressure side or lower then you will need to change the fuel pump.

What plugs are you using,did you try a NGK CR8E?.

When you remove the plug,is it wet with black oily deposits or is the plug dry with a black deposit,also check if the plug has a greyish white appearance,is there deposits between the two electrodes....?If you can give more info maybe I can assist.