Can't get Generator to run right!

Joined
Nov 27, 2017
Messages
27
Location
Massachusetts
Well, it's wintertime again here in New England and I'm just waiting for a storm to knock off my power for a week or two without a generator. I have a generator that will only run with the choke on and even with the choke on, it sometimes stalls after a few minutes. My brain automatically goes to it running lean. Here are the symptoms and things I've checked on. Any advice would be greatly appreciated since I'm absolutely baffled. I tried battling this thing a year ago with no luck. I'm giving it another shot. There must be some stupid thing I'm forgetting or missing.

Gentron 10020 Generator 420cc 15hp.

- Air filter is clean
- Runs the same way without air filter on
- It stalls when choke is off.
- Runs kind of right when choke is on, but not quite. Also, may stall after a few minutes.
- Spark plug is new and correctly gapped
- Was running fine last time I had to power the house. Then after a year (or maybe two) in storage, it was doing this odd behavior.
- I put it in storage with fuel stabilizer and I fogged the engine
- All old fuel has been drained and fresh fuel has been put in. I can 99.99% guarantee it is not fuel quality related.
- Adjusting the carb didn't remedy it.
- Bought a replacement carb, runs the same.
- I adjusted the valve lash to factory recommended. Even so, the valves were barely out of adjustment prior to doing so.

After starting it today, it smoked like crazy. Then slowly cleared up. I don't remember fogging up the cylinder wall this last time, but I must have.

What is the compression test supposed to come in roughly on an engine like this? I did a compression test last year, but I can't remember what it was. I think it was 80 psi cold, but I can't remember. I just remember thinking it was low, but still should be able to work. I also can do a leak down test.

Any ideas on what to look for? My brain keeps telling me it MUST be carburetor related, but I've done everything I can think of. Could compression loss create this issue?
 
Go thru the basics first. Do you get adequate fuel flow to the carb, is the fuel trash and debris free at the carb, when you open the drain on the carb bowl does the fuel flow freely. New parts are supposed to work perfectly but...... Is the tank adequately vented. Then look for air leaks. If the carb has a spacer is it still free of cracks or pinholes, are the gaskets on both sides sealing tight. Any place else extra air can get in etc.
 
Compression around 60-80 is fine. The engine has a compression release valve.

I just watched this video today. This guy has a channel fixing up old broken generators. This might be the same generator as yours?

In this case the generator would stall shortly after starting. He found the spark arrestor clogged with carbon and broken. Once he removed it off the muffler it ran fine.

If you checked everything else, this might be worth a look.

 
Does it have a vacuum leak of some kind? If it runs with the choke on, it has to be getting air from somewhere else. Here is a link to a thread in a power equipment forum, with a similar problem with a Honda generator. Perhaps some parallel lines can be drawn as to a solution.

Thank you so much! I'm going to be checking that guy's thread. It is the EXACT same thing I'm going through. I'm hoping he figures it out. I might just register and subscribe to let him know I'm dealing with an identical issue.
 
Compression around 60-80 is fine. The engine has a compression release valve.

I just watched this video today. This guy has a channel fixing up old broken generators. This might be the same generator as yours?

In this case the generator would stall shortly after starting. He found the spark arrestor clogged with carbon and broken. Once he removed it off the muffler it ran fine.

If you checked everything else, this might be worth a look.


yup. Same exact one! I can't wait to see the video.
 
OP says it runs the same with a new carb?

Im voting exhaust or gas or air intake restriction. Maybe run without gas cap to rule that out, but I suspect its the spark arrestor, as already suggested.
I had a Honda 125 that ran like this and after everything else was checked it turned out to be the gas cap wouldnt vent. A 1/16 dia hole drilled in the cap and it ran like a champ.
 
No guarantee of getting a Chinese knockoff carb good out of the box.
Yes I had one where the bottom bolt was too long and it blocked flow through the jet, starving the engine similar to what the OP is experiencing. I would try cleaning and reusing the original one. Also with the fuel line disconnected from the carb, open the petcock and make sure there is good flow from the tank and that the gas is clean and not too stale.
 
OP says it runs the same with a new carb?

Im voting exhaust or gas or air intake restriction. Maybe run without gas cap to rule that out, but I suspect its the spark arrestor, as already suggested.
i'm really leaning towards clogged spark arrestor. Only thing that kind of confuses me is wouldn't the carb run richer with a poorly flowing exhaust? As opposed to my situation where I have to choke the carb to get it to run.
 
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i'm really leaning towards clogged spark arrestor. Only thing that kind of confuses me is wouldn't the carb run richer with a poorly flowing exhaust? As opposed to my situation where I have to choke the carb to get it to run.
I’m thinking the vacuum signal could drop, and then not pull gas properly. Choking either increases that vacuum signal, or pulls in another circuit.
 
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