Engine needs some choke all the time?

[KingCake]

I have a 7Kw briggs generator with a 420cc B&S single piston engine.

Once the engine is warmed and I turn off the choke it starts surging up and down in RPM very rapidly. If I give it about 1/4 choke it purrs like a kitten even at full load.

It only has about 60 hours on it. Air filter is clean. I never let the gas get too old and I always put in stabil with ethanol treatment (marine stabil). I pulled the plug it looked brand new and the gap was correct.

Is this normal? I'm not familiar with these bigger air cooled engines.

 

[ted s]

its running lean from a carb problem

 

[KingCake]

I wish it had an obd2 port for me to pull some fuel trim readings lol.

So what should I try first misting some carb cleaner through the intake while it's running?

 

[Pop_Rivit]

Pull the carb, clean it, and put it back. Those little carbs are extremely simple to work on with just a few basic tools.

 

[Colt45ws]

Agree with pops. Remove and clean is the way to go here.

 

[demarpaint]

On occasion my snow blower carb will go out of adjustment from vibration, causing the problem you described. I just adjust the air fuel mix once the engine is warmed up and under load. Problem solved. If an adjustment doesn't work for you, as others mentioned pull the carb, and clean it.

 

[Merkava_4]

Typical typical typical. If the engine needs choke, that means it's getting too much air for the amount of fuel it's getting. Increase the fuel supply and the engine won't need the choke. Your carburetor needs cleaning.

 

[MDettling]

Originally Posted By: KingCake
I wish it had an obd2 port for me to pull some fuel trim readings lol.

So what should I try first misting some carb cleaner through the intake while it's running?


I work in the small engine field, and agree that its running lean. Gunked up carb jets maybe.

Seafoam the gas tank.

In fact, theres new OPE already out with OBD, think it was Kohler.

 

[Donald]

Buy a rebuild kit and then clean and rebuild the carb. You probably do not need the rebuild kit, but handy to have if a gasket gets torn or looks dried out.

How do you shut it down? I would run the carb out of gas regardless of using Stabil.

 

[The_Jeff]

There's no great way to store OPE; I've tried all the classics except a pint of AVGas.

You might be able to pull the carb bowl with the carb still connected and shoot some carb cleaner (can with red straw) up the main jet without removing said jet.

Generator carbs are pretty simple stupid because they don't have to idle or run any speed other than 3600 RPM.

 

[HerrStig]

Pull the float bowl. There's a little hole in the bottom which allows fuel to flow from the bowl into the tube which supplies the jet. That tiny hole often clogs with gum, at least on the Walbro carbs. A good dose of Berrymans might clean it without removing the bowl. If that hole is clear then the main jet should be checked for a clog, which will require carb removal. On most older B&S engines it's easy. If the idle jet is clogged the engine won't idle well, but non-inverter gensets don't run at idle rpm, they must maintain 3600 plus or minus to keeep the ac frequency at 60 Hz.

 

[HerrStig]

I have to ask, what are we coming to when people can't troubleshoot a one lung air cooled generator engine without an OBDII?

 

[Brybo86]

The carbs pilot/idle circuit is clogged.

Clean the carb.

 

[krismoriah72]

I like to do the simple stuff first. Pull the old gas and install fresh 91 or higher octane gas. I have 'fixed' many family and friends OPE due to the older gas issue.


Wouldnt hurt to read the plug and possibly install fresh one due to 60hrs.

 

[spasm3]

Originally Posted By: Brybo86
The carbs pilot/idle circuit is clogged.

Clean the carb.


My experience is that the carb needs to be pulled and all orifices cleaned. I have not had success with dump in the tank cleaners even berrymans when it only runs with the choke on.

 

[demarpaint]

I'd try a carb adjustment first, especially if the gas in the tank is good. Many times they go out of adjustment just from vibration. If that doesn't work then tear into the carb and clean and or rebuild it. It's really a simple job when you get right down to it.

 

[punisher]

Originally Posted By: HerrStig
I have to ask, what are we coming to when people can't troubleshoot a one lung air cooled generator engine without an OBDII?


From the early 90s on up we had helpers/trainees in the shop(Ford dealership) who had no experience with carburetors. The few times I went through a Motorcraft(often a horrible VV)/Holley/Q-jet, one or more would look over my shoulder and fire questions as I went through it. An old Honda CVCC Keihin would have warped their precious little minds.

First grab the carb and make sure it isn't loose. Fixed a fair amount of surges/vac leaks just by snugging up loose mounting bolts, then you can clean the gunk out of it. At least no one brought up "governor" as a cause. We're getting better.

 

[SHOZ]

Had a snow blower that needed more and more choke. Turned out to be the flywheel key on the crankshaft was almost sheared and the timing was way off.

 

[KingCake]

Originally Posted By: HerrStig
I have to ask, what are we coming to when people can't troubleshoot a one lung air cooled generator engine without an OBDII?


It was a joke. I understand that some choke to run well = too much air.

Originally Posted By: krismoriah72
I like to do the simple stuff first. Pull the old gas and install fresh 91 or higher octane gas. I have 'fixed' many family and friends OPE due to the older gas issue.


Wouldnt hurt to read the plug and possibly install fresh one due to 60hrs.



Read my post. I did all this already.

Originally Posted By: Donald
Buy a rebuild kit and then clean and rebuild the carb. You probably do not need the rebuild kit, but handy to have if a gasket gets torn or looks dried out.

How do you shut it down? I would run the carb out of gas regardless of using Stabil.


I alway disconnect electrical devices from it, shut the fuel petcock and let it stall out.

 

[KingCake]

Originally Posted By: demarpaint
I'd try a carb adjustment first, especially if the gas in the tank is good. Many times they go out of adjustment just from vibration. If that doesn't work then tear into the carb and clean and or rebuild it. It's really a simple job when you get right down to it.


Ok thanks I'll try that. This is the kind of thing I wanted to know before I full on stripped the carb.

Originally Posted By: punisher
Originally Posted By: HerrStig
I have to ask, what are we coming to when people can't troubleshoot a one lung air cooled generator engine without an OBDII?


From the early 90s on up we had helpers/trainees in the shop(Ford dealership) who had no experience with carburetors. The few times I went through a Motorcraft(often a horrible VV)/Holley/Q-jet, one or more would look over my shoulder and fire questions as I went through it. An old Honda CVCC Keihin would have warped their precious little minds.

First grab the carb and make sure it isn't loose. Fixed a fair amount of surges/vac leaks just by snugging up loose mounting bolts, then you can clean the gunk out of it. At least no one brought up "governor" as a cause. We're getting better.


Good idea. That big single piston engine vibrates like a sumbitch.