Small engine problems

I have a Honda GX390 on a 6kw generator. Since its a generator it has sat a year with stabilizer since last used. The engine starts and runs great for 30 seconds to a minute then shuts down. It will restart but has to wait about a minute to restart.

I have pulled the drain on the carb bowl and have good fuel flow. I pulled the bowl plug immediately after it shut down and I have fuel at the bowl after shutdown. I have also disconnected the low oil switch.

Ideas?

I have seen Honda's act like that from varnish, will it run longer with the choke on? I would imagine you have tried that, unless it has some kind of automatic choke. It could also be an ignition problem, I had an older outboard than had similar symptoms and it was a condenser, but I imagine this one is electronic, but it still had a condenser.
If it were mine I would put some Sea Foam in it and take the air filter off. Then start it and dribble enough fuel into the carb to keep it running. I have special bottle that I use to safely dribble a small amount of fuel with. If it will run continuous that way it means it's not ignition and probably varnish in the fuel system, and the Sea Foam should take care of that. The only time I ever used fuel stabilizer it seemed to cause more problems than none, so no more for me.

Yep you still have either reduced fuel flow from the tank to the carb or ya have junk in the carb from the old stale gas . I go thru this every spring with the lawn mowers for the last couple years . Friend of mine and his wife own a Sear home town store and one day he showed up at my house and dropped off five new mowers and two New or i should say lightly used mowers that people brought back because they did not run and the Sears service tech messed with each one for like five min. and said scrap them and give the customers NEW ones and to throw the old ones in the dumpster as they were junk. The following Sunday afternoon armed with a hand full of tools and a spark tester and fresh gas i went playing with them . First test do i have spark YES , i know i have gas , i have gas at the carb , so if there is gas at the carb but it still does not run then the gas is not going thru the carb . and on four of the mowers the main jets all had what looked like clear grains of sand stuck in them . A poke with a torch tip cleaner and a lawn mower inline fuel filter and four ran on first pull . The fifth mower took a bit more work and a new blade as that one the owner hit something and bent the blade and sheared the crank KEY . I had to walk across the street to the neighbor and got a Briggs crank key off of him and it ran . The two snow blowers were the same issue junk in the main jets.In the matter of two hours and two beers i had them all up and running . I kept two and last year i had to do the same thing with the carbs even with the inline filters on both of them , both started on first pull and ran for maybe ten min.'s and died and once again the main jets were plugged with the same grainny stuff.

To combat this problem, I have started buying 91 octane fuel with NO ethanol and use that in all my small engines. It's $4 a gallon, but I don't want or need problems each spring. I have found that a product called Ethanol Shield does a good job of keeping fuel from going bad, and a sister product called "Mechanic In A Bottle" is absolutely miraculous for cleaning crudded up fuel systems. I've found them at Menards and Tractor Supply. I've had good luck with Sea Foam, also...

Thanks, I will give the extra dose of gas to the carb and see what happens as choking it does not get me any extra run time. There was a small amount of granular varnish in the carb bowl when I had it off yesterday but I have seen running engines with more.

After dealing with this I have thought for the little bit I use this I should use aviation gas. I don't think there is non ethanol gas available in this area.

Once you have eliminated fuel flow as a problem, disconnect the on/off switch along with the oil sensor switch. If that still doesn't make any difference, it's time to start checking out the ignition system. The problem as you describe it could be fuel flow, but running a short time, quitting and then starting again after a bit is also an indication of a bad coil. It is not uncommon for ignition systems to fail after sitting unused for a few months. Good luck.

pull the bowl off the carb. right in the middle, where the screw for the bowl went, reach a small flat head screwdriver up there and remove the main jet. there will be 2 pieces, the jet itself and the brass screw that retains it.make sure all holes are clean. torch tip cleaner works great for that. also, make sure there aren't bits of corroded metal floating around in the bowl.

Thanks you have saved me a lot of carb disassembly time due to how its placed in the frame of the generator. I didn't realize the main jet was so easy to get to. I can get to the bowl very easily but it would be a chore to completely disassemble the carb.

I am starting to think more towards a bad ignition just need some time to work on it now.

I would suspect an oil pressure switch issue.

At work we had a mobile pressure washer, was ok when parked in the fall, wouldn't run in the spring. The carb. bowl was full of some jelly like stuff and corrosion, cleaned it the best I could and didn't have much hope but it never bothered again while I was still there. Some body must of dumped something in the tank before storing.

Two things.
1 Take the extra time to pull the carb and clean it. It's not that hard to tear down. Spray sea foam or ether in all the ports and blow them out. Got that same engine on my lawn vac. BTDT.

2 Check the short fuel line and make sure it isn't collapsed.

Good Luck.

gab, i have seen that jelly like stuff and i swear it has to be from ethonol.

I had a problem like that one time. The spark plug looked new, but it was bad.

The gum is not from the ethanol. It's from the crappy gasoline they blend the ethanol into to bring it up to 87 octane. Ethanol, as I understand is pure alcohol that has been tainted so humans can't drink it.

I have about 18 Honda engines from 5 hp to 24 hp. They are pretty solid and with basic maintanence I want them to start on the second pull after 6 months of sitting.

If you work out that it is not fuel I would start looking at electric / ignition issues.
You said the low oil is disconected, good first step although you should check the oil level anyway.

The first thing I do is put a new plug in. I use NGK BPR5ES. I have found just changing the plugs will solve the problems 80% of the time.
When you have the plug cap off, look inside. Take a broad flat screwdriver and make sure the contact inside is tight. Sometimes they wiggle loose a bit, behind it is a fuse / coil contractor.... I've only had one of these go bad, but I have had the screw connector loosen up.

You say you're taking care of the fuel so it probably isn't that.... but you never know. There is also a filter inside the tank attached to the pipe nipple on the outside. I have had very dirty stuff plug it up... but unlikely in your case.

Let us know how you make out. Good luck, Grant

Here is what I would do to determine if the spark was the culprit whether it is a coil, oil sensor etc. Now hopefully you have a spark plug with grooves in the porcelain, get about six inches of 14 gauge bare solid copper wire. Make one wrap around the plug porcelain leave about a 3/4" tail on the short tail of the twist. After the twist is tight take the short end and bend it up toward the bottom of the plug terminal to less then a 1/16" away. Now the goal with the longer end is to be able to bend a U in it to fit reasonably tight in the terminal plug on the spark plug wire. Of course trim as needed to fit and connect to the plug wire. Now again check your short end gap to to terminal to be the 1/16" or less. The purpose of this is to be able to see the spark jumping this gap to the terminal while the engine is running. If the spark stops when the engine shuts down you know the cause is the ignition or safety shut off not the fuel.

Change the spark plug. I had one that acted like that I was sure it was running out of fuel somehow. It would run until the spark plug got to a certain temperature and then quit. When the plug cooled off a little it would star.

Take the carb off and apart and clean it. It is easy to do and very few parts to disassemble. At one year without running, you will be very lucky to get it to run right otherwise. I just did this to mine (same engine on a generator), before I left for Florida and it took about 1 hr. start to finish. If you are careful, you will reuse all the gaskets. My carb had torques head studs under the nuts holding the carb on. I was able to remove them with a small 12 point deep well socket.