Surging Yamaha EF2800i

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Surging Yamaha EF2800i

shutterbug
My Yamaha EF2800i generator has begun surging in both the "Economy" mode and the "Normal" mode. It has run flawlessly when I test it monthly since 2005, until now. The surging is very noticeable in the "Economy" mode, but will smooth out fairly well in the "Normal" mode by adjusting the choke slightly on.
I have disassembled the carb, sprayed with carb cleaner, used tiny wires in every jet---even the very tiny holes in the carb body, and have blown everything out with the air hose three different times. The unit starts on the second pull, even when i've run all the gas out and it's just been turned on. Incidentally, I have always used a fuel stabilizer and have also recently switched to non-ethanol gasoline.
I've cleaned the air filter and the spark arrester. Suggestions please?
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Re: Surging Yamaha EF2800i

Grumps
Here is a good thread to read,   EF2800i Hunting by GlenInIdaho

This sounds just like your problem, Cyclerob always has some good info to share.

I find that it is better for perodic testing to put about a pint of fuel in the generator and let it run till all fuel is used then drain the float bowl. I keep my non ethanol fuel in  separate containers with stabilizer and every six weeks I put that fuel in my truck and refill the containers. I have found that even with stabilizer fuel just doesn't last very long and it will cause gum in the carb jets and carbon buildup on the valves. I have the same engine in my EF2400ishc and have had no problems by running the unit dry before storing it.
Good luck
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Re: Surging Yamaha EF2800i

Niky
In reply to this post by shutterbug
Yamaha EF2800i generator hunting/surging with 500W load in eco-mode. Throttle spring tension.

The previous owner got the problem with “rough running” and replaced carburetor, but it didn’t fix it. I read all the forums, but it was always about cleaning carburetor, and it’s not applicable to me, since the curb was replaced with a new one.
I was ready to replace a $700 Control Box, but by luck found somebody’s post about throttle spring tension. I want to re-post this FIX.

"If you EF2800i is running relatively smooth with no load in eco-mode and hunting with ¼ - ½ load, you can increase throttle return spring tension by making one more turn on it. Return spring is a multi-turn coil, just tight it with one more turn".

In my case it was working like a charm. No more hunting and $700 saved.
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Re: Surging Yamaha EF2800i

CycleRob
In reply to this post by shutterbug
shutterbug,
 When you said:
 "The surging is very noticeable in the "Economy" mode, but will smooth out fairly well in the "Normal" mode by adjusting the choke slightly on"
 that says the pilot jet fuel mixture is too lean and that will always cause the RPMs to cycle. It may just need the plastic capped pilot adjusting screw turned outward (CCW) to richen the mixture. If it is already at the limiter stop, the pilot jet and adjuster screw's needle taper and/or needle seat will need cleaning. You said you cleaned all the jets, but you may have unknowingly omitted the pilot jet cleaning. Since removing the carb and taking it apart just to clean the pilot jet is too much work for a frequently required servicing, they made the pilot jet easier to access from the outside. That "hides it" from the inexperienced tinkerers. You find the pilot jet by removing the screw that screws downward into the top surface of the EF2800i carburetor casting. I cannot tell from the EF2800i parts diagram if that is the actual pilot jet or if it's a screw that provides access to the pilot jet's screwdriver slot or the metering orifice of a pressed in jet. Some newer carbs now have a removable plastic jet, which is immune to corrosion, cheaper to replace and less likely to get gummed up.

Other less likely possibilities for RPM cycling are:
-- Old gasoline, the necessary volatile elements have evaporated.
-- A perforated/crumbled air filter foam element. That damage leans out the entire mixture range.
-- An out of spec (too tight) valve adjustment.
Talent, On Loan, From God  --Rush Limbaugh--
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Re: Surging Yamaha EF2800i

TheLungMD
First post here, but I wanted to echo the success of the prior post in hopes of helping the next guy with the same issue.  

My 2004 Yamaha EF2800i was surging (hunting) when a decent load was applied during Eco mode running.  No problems with the eco mode turned off.  After cleaning the carb and TINY pilot jet twice (and endless playing with the pilot jet screw adjustment) there was simply no improvement in the surging/hunting.  

I removed the DC stepping motor from the top of the carb and added 1 wrap of tension to the throttle return spring.  You have to gently coax the spring's bottom arm/hook around the throttle arm and then put the spring's hook back in the hole where it was.  Adding ONE turn (counter clockwise) of additional spring tension completely fixed the Eco surging problem in my generator.

As other have said, you have to manually hold the carb throttle plate in the wide open position when re-installing the carb's throttle motor into its plastic slot.  

Thanks again!!