Messed up new honda engine? Why?

[Shadow_storm56]

So we put a brand new honda engine on our strawberry weeder and for some reason it's all outta wack. Blows black smoke, no power, back fires... the only thing I did was loosen the fuel bowl enough to drain the fuel and tighten it back. The gas went rotten in the time it was sitting in our shop. Acts like it has diesel in it but I put gas in it myself, I think it's gx390. Help plz

 

[MOOTS]

Is the choke on?

 

[Shadow_storm56]

Is the choke on?

Haha I wish it was that simple but no. It acts like it is

 

[MOOTS]

Air filter good? No plastic around it? You said engine was new.

 

[Shadow_storm56]

Air filter good? No plastic around it? You said engine was new.

They got it all ready when It arrived in the shop.... started it and such. I'll check that but I assume honda powerhouse would know enough to remove the plastic.

 

[MOOTS]

How long has it set before this problem started? You said the gas was rotten in it. Did you pull carb and clean? Could have a tiny speck of something in the jets. But maybe not, as black smoke is unburnt fuel.

 

[Shadow_storm56]

How long has it set before this problem started? You said the gas was rotten in it. Did you pull carb and clean? Could have a tiny speck of something in the jets. But maybe not, as black smoke is unburnt fuel.

Maybe 2 months, I didn't clean the carb though... very strange

 

[xrocketengineer]

Could the fuel float needle have gotten stuck when you loosened the fuel bowl?

 

[NCL4701]

For a little gas engine such as a Honda GX390 or anything similar, it needs 4 things to run: spark, fuel, air, compression.

It is sort of running so compression is all but eliminated.

Spark: if it’s running fine cold and messing up when it’s hot I’d revisit the electronic ignition module but that’s not what you describe.

Air: I’d take the air cleaner off while the engine is somewhere where the air isn’t incredibly dusty. Start the engine. Watch the choke plate (not the control knob or whatever controls it, the actual plate in the carb throat). If the choke is operating normally and the problem persists it’s in the fuel side of the carb.

If the air and spark are eliminated that leaves fuel. Not much that will cause excessive fuel: choke not releasing (eliminated above); jets misadjusted (makes no sense unless someone messed with it since it last ran right); stuck float (quite possible); generally gummed up carb (not highly likely but possible).

I suggest take off the air cleaner, run it without it long enough for choke to come off to check choke operation and eliminate the air filter, air box, and anything else air related. If no change in symptoms with air cleaner assy removed and choke operating normally sounds like a carb cleaning and inspection of float is in order.

 

[Chanceywd]

So we put a brand new honda engine on our strawberry weeder and for some reason it's all outta wack. Blows black smoke, no power, back fires... the only thing I did was loosen the fuel bowl enough to drain the fuel and tighten it back. The gas went rotten in the time it was sitting in our shop. Acts like it has diesel in it but I put gas in it myself, I think it's gx390. Help plz

Is it possibly oil from the engine being tipped the wrong way during handling or installation? I did that recently changing a push mower engine and the oil from the crankcase got into the crankcase breather tube making quite a problem getting it to run until it cleaned out.

 

[re54drider]

Maybe 2 months, I didn't clean the carb though... very strange

Bad gas will clog up the fuel system and, in my experiece, will not clear with new gas. I would suggest cleaning the working parts of the carb. Completely drain all the gas and start anew.

 

[Tughill Tom]

You'll need to clean the Carb and fuel system, find non-ethanol gas and high octane and run it like you stole it.

 

[Jim L.]

X3 on ethanol gas being the problem. Carb needs taking off, apart, and good cleaning.

Non-ethanol gas if you can find it. Otherwise put fuel stabilizer in to prevent clogging.

 

[JWool]

Agree with get some non ethanal gas, around here its called REC Fuel at the stations that have it.
or some VP 4 stroke or similar from like tractor supply.

Small engines are horrible with the ethanal gas the Alcohol seperates and swells rubbers seals.
Once I started using rec gas or VP in all my small engines they start right up after sitting and run great.

 

[MOOTS]

I run all of my OPE on non ethanol. Mower, weed eater and chainsaws. They start every time. Everyone should. Price is a bit higher, but in small use stuff it’s much cheaper than rebuilds.

 

[GreensvilleJay]

You need to clean ENTIRE gas system, tank, new lines, carb,etc. Expect to waste 3-4 hours of your life getting rid of the mess ethanol has made. 'gas' with any ethanol in it has less BTU(hp) for the ounce, absorbs water out of the air and will attackthe fuel system components. 'silly' things like the water it acquires, sinks to the bottom of the tank, so it's FIRST into the carb, and if bad enough engine won't run. You call it quits for the day...next time, it won't even start.....carb gets bunged up due to corrosion.... yeah water reacts to the brass,tin, steel,aluminum in the carb,causing even more grief. Luckily the Chinese carbs are only $20.....
Cure, once totally cleaned out... use NON Ethonal HItest with fuel stabilizer AND when done, shut off tank, run carb 'dry'.