10HP Subaru/Robin gas on generator engine only runs smooth with choke half on, what can cause this? also the extra jet on the outside of carb what does it do?

Unclear when stated that there is a governor issue? I assume you have a Robin/Subaru 7.5 H.P. engine model EY280YD2510 with erratic behavior leading up to stalling out when a load is applied or the generator is at no load status after several minutes of run time?. Couple of things to check would be starting with the fuel system. Is there stale gas in the fuel tank? Have you verified fuel flow from tank? Is the fuel cutoff valve free of debris? Is the carb fuel bowel been removed and inspected for varnish? Is the air cleaner clean? Next, Ignition system. Have you inspected the flywheel for excessive rust? Have you reset the air gap on the ignition module? Does the on/off switch work (measured with a meter for continuity?) Any visual signs of damage with all wiring or the ignition module itself? I once thought I had an governor issue where the issue ended up being that the flywheel was corroded to the point that once the engine was fully warmed up the control module would contact the rust build up on the flywheel causing engine surges no matter what the load was on the generator, and at times would stall the engine. Clean flywheel off if necessary and reset the air gap on the ignition module. If that fails then inspect the governor spring (the top spring on the carb. linkage assembly) for excessive rust that will change the tension on the governor arm.Replace if in doubt! When doing all this inspecting ensure you have fresh fuel, oil, air filter, spark plug gapped correctly, and ignition module that has been tested as sound! These Robin engines are smooth running heavy duty engine that will perform for many years if taken care of. Good luck!

Hi Joe, I had asked for a little clarification and have not received any information. I will answer this question based on the generator is in good working order and it is a recoil start. Open the petcock, (this is the fuel valve) and give it about a minute to fill the fuel bowl on the carburetor. If your generator has an engine an on/off kill switch, set to on. If the generator has an auto idle switch set it to off. If the engine has a throttle lever located under the carburetor, push it all the way down (full throttle). Pull the choke knob out completely, there is a detent on the choke for half choke, pull it past this for full choke. pull the recoil starter rapidly. As soon as the engine starts running push the choke knob to half choke, this will allow the engine to run smooth while it's warming up. Depending on the climate that you are in, warm up time will vary. After a minute or two in cold climates start pushing the choke knob in, if it starts to run poorly pull it back out too the half position and let it warm up some more. When you can posh the choke in without the engine faltering it is ready to go. In warmer climates you might be able to start the engine without the choke or in the halfway position. Robin Subaru makes some of the finest small engines available. I would choose a Robin over a Honda every time. I hope this gets your generator going, and once again this is based on the generator being in good working order. Good luck, Michael Burke.

Sounds like the carb is dirty. Try running the generator for a bit and when it sputters try slowly closing the choke to see if the generator will come out of its sputtering. If it does come out of it then you can start at the fuel tank and remove the filter screen in the tank and clean it well with an old toothbrush. If it is plugged with varnish it needs replaced. You can get by testing the unit by leaving it out and reassembling but you will need to replace it before actually using the generator. If the filter is clean check fuel lines for plugging and varnish along with the inline filter if it has one. If the lines and tank are clear you will need to pull the carb off, remove the bowl and clean the carb and jets. You may need to use a commercial carb cleaner if varnish is bad but be sure any plastic or rubber parts are removed before cleaning. Only immerse the entire carb if it is necessary. Try to remove the jets for cleaning. They can be a pain at times to remove but the jets and bowl are safe to immerse in carb cleaner. If the rubber o ring sticks to the bowl remove it before putting it in cleaner.

The reason choking the generator works when jets or fuel lines are plugged is because the choke blocks most outside are from entering the carb causing the engine to "****" harder through the jets in the carb.

if you are running the engine at full CHOKE, then it is flooding the engine, but if you meant off full choke, then the carb is still stopped up. Try soaking in carb cleaner overnight after removing jet & all rubber goods. HOPE THIS HELPS.

take out the jets , and run small wire through all holes .should fix your problem

it has a blocked fule line and maybe blocked jets in the carb first clean all the fule lines from the tank down check the filter in the tank as well they do get rust in them, if fule is reaching the carb strip carb and clean all jets,, dont go poking wire into the jets it could distroy them check that the flote is free and lifting then clean the air filter and try starting it up,,,it should run ok then

Fuel system needs cleaned. Dirt or build up get's in the passages and it can not properly regulate the fuel/air mixture. Being it runs well in choke position I would suspect it is plugged on the idle passage. Sometimes you can add a very small amount of "Seafoam" to the fuel and let it run while slowly moving the lever to the run position and this will clean it out. It is also possible that the fuel tank has a small amount of water in it. Good luck and have a great day.

A fuel starvation problem.
Pull the fuel line off the carb..........the flow should be strong from the tank.
If not check for a blocked filter or fuel switch not allowing full flow.
If you do have a good fuel flow.......the restriction is in the carb.......a good cleaning will be next.
Usually it is the main jet that is semi clogged from storing the engine with out shutting off the fuel and running the carb dry.
After cleaning make sure all fuel in the tank is fresh.

A call to Elliott Small Engine solved my problem - Oil Guard. I had checked the oil and it was just a little low but seemed well within the normal range. I was told to add more, bringing it just over the Full mark. It seems that the low oil protection system is very sensitive and shuts down the engine even when the oil is withing 1/8" of the mark. I added about 2-3 oz of oil and no more problems

The first thing I want to say is this.

If you have a chance to dump this Robin/Subaru Genset please do so!

I say this because the Manual docs for these R/S engines and/or Gensets are so poorly written in comparison to say Briggs & Stratton or Honda engines that it's like DAY and NIGHT in comparison.

My personal GENERAC 5500 Genset (that uses a B&S 10HP engine) Users Manual is like a Chilton Auto Manual in comparison to the R/S literature. No offense, but it's the truth!

It would be nice to have the WHOLE engine model # for starters, but seeings it's a 10hp Robin/Subaru it no doubt doesn't even have the TORX head style Carb bolts/studs requiring Torx sockets.

If it does by chance - then I'm not sure what size they normally are, as I don't have the exact model #, so I guess you're on your own there and will have to find a set of Torx sockets first.

If the Float Bowl has no Main Jet external adjustment screw assy at the bottom of the Float Bowl, or retainer bolt/nut, then the Float Bowl is screw threaded on in a CW direction.

You may have to use a rubber sleeve (like a 2" cut piece of rubber inner tubing from an old bike tire) and slip it over the bowl to help unscrew it. A smaller rubber band type wrench will work also, but I would hand tighten it so as not to damage anything.

It shouldn't be tightened on that tight to begin with. Be very careful replacing it and the seal gasket (or sometimes an O-ring) making sure the threads are lined up exactly right otherwise you will cross-thread the Bowl or the Carb Body!!

I can't be any more help then that, as that's all I have to work with here.

Let me know if that does it?

Post a reply here please.

Thx and best regards,

Frank