Small engine Gurus- Troubleshoot question ?????

Honda GX 390 on a Miller welder.
Starts on first pull cold or hot.
Idles fine
Runs wide open fine
Have always used E free fuel
30 seconds under load it starts sputtering and dies
Starts right back up first pull. Sometimes it takes a second pull

At first I thought it was fuel
Took tank off and flushed it. A little crud in bottom but not much
Took bowl off carb and cleaned
Put half a gallon in tank with seafoam and let idle for half hour minimum
Ran it wide open 5-10 minutes (no load) ran fine
Tried welding with it today
Same symptom
Next plan of attack
Check for crack in fuel line. Im wondering if when its really pulling fuel it gets a surge of air in fuel line
That don't pan out a carb rebuild is up next
Any ideas????

 

Still a piece of dirt somewhere? My splitter with a Honda 160 does the same thing from time to time. I flushed out the tank this spring but I think there are still bits in the system. It's put to bed for the winter now but when I get it out next spring I will flush again - this time also flushing the fuel pump. I didn't touch that before. I will also find a small fuel filter to put on it. If you didn't take the carb off & apart you might still have something in a jet.

 

I'm nowhere near a small engine guru but I've worked on my own dirt bikes (2 strokes and 4's) pretty much my whole life. Through my travels I've noticed one pattern that generally works the best on problems that are not immediately obvious. Start with the cheap/easy stuff first and work your way towards the expensive/complicated stuff. Unless you have testing equipment (which most of us don't) it will always come down to a process of elimination so to me it makes the most sense to methodically eliminate the possibilities by starting with the cheap/easy stuff first. I've noticed that generally consists of:

1. Spark (doesn't sound like an issue here)
2. Fuel
3. Air Intake
4. Exhaust
5. Compression
6.Timing

From you've described you're on the right track. Check the fuel line for cracks or decay and if there's a filter swap it out. I had a blower do what your describing and the fuel line was in the process of failing so it would start but not run. For me I keep some lying around as it's such a common problem with chainsaws. If there's an intake manifold check for cracking or gaps (sorry not familiar with your rig so flying blind). If that looks ok then I'd move to a carb rebuild or cleaning and so on... Good luck!

 

Sounds like it is running out of fuel, could be a kinked fuel line restricting flow, or dirt in the float needle/seat area, hard to say for sure. I assume it is a gravity fed system? Also could be the coil heating up and conking out...but my first guess is low fuel flow...

 

I've got a half dozen of these engines, and my problems are usually at idle. A good dose of Seafoam works, but it needs to sit awhile in the carb. I've let one sit a month and it's worked fine since. Not sure if 2 or 5 days or 2 weeks would've been long enough to get it to work. If I need it in the meantime, I run it at 1/4 or 1/2 choke or whatever setting makes it run the smoothest

 

Governor spring or bracket it is attached to

 

I think your onto something.
Gonna start here

 

If you can give it a little choke when it starts to sputter, and it smooths out for a bit, then it is fuel related...doesn't sound like governor to me...that wouldn't make it sputter and die, just bog when more power is needed

 

I am leaning toward a spark or coil problem if it is under load.

Gary

 

Look and see if there is a screen or fuel filter some where. Next I would check the fuel tank vent. You can run it with the gas cap loose for checking the vent.

 

Just had a similar issue with a neighbors generator I was asked to fix - similar symptoms - fully cleaned carb, new fuel line, cleaned tank, etc. and same issue. Same problem. Turned out to be idle screw turned out too far and never thought to test this by turning it in before doing all the other work - ugh. Cheers!

 

Checked

 

One thing I forgot to mention .
When it dies out under brief load ,,,, it will kick the choke lever to full choke .
I tried zip tying it and the motor will still die .
Governor spring ?????

 

Choke or throttle lever?
Gary

 

Many Hondas have a small sediment bowl on the bottom of the fuel valve that can be unscrewed (10mm wrench) and cleaned...

 

Count the turns to seat the high and low screws then remove them. Blast carb cleaner and a gentle blast of compressed air into the holes, replace the screws to the same setting and give it a shot.

 

Checked

 

Choke

 

The ones I have use a fixed main jet. And the low only moves 1/8 turn. But if they're clean, they never need adjustment. Mine are between 15 and 25 years old run on pump gas and 1oz of Seafoam per tank. No more problems