portable generator surging

leftlane

New User
the engine on my 3500watt generator keeps surging(revving up and down).last spring I put it into storage with clean gas and stabil,ran it a little while then shut off fuel and let it run out of gas.recently needed it, started it up and the motor kept surging over and over.i drained fuel put clean fuel in,took carb off blew out and cleaned with carb cleaner.still has same problem. I used a small pair of vicegrips to clamp throttle in a fixed position and it runs smooth.what should I check next.troubled.please help. ps generator two years old
 
Take the vice grips off. Because you are over riding the Gov. Which can burn things up.Most common cause for surging is a dirty carb. Needs to be removed and soaked for a day.Also carb may not be repairable.Some are not.What generator is it.
 
Every time I've had a small engine surge, it's been the idle circuit or low speed circuit in carb is blocked. Engine begins to die, governor opens up throttle plate and then it speeds up.

One exception, I purchased a used go-cart, found the bolts holding the carb in place were lose.

But when you hold thing in place with vicegrips it makes me wonder what is really going on. Like is there a spring missing or governor out of wack??? no Idea.

Would the surging stop if you used some choke?

Many manuals say drain carb when storing. Many people on YT will say I'm wrong. In the past 50 years, I never have and never will leave anything empty. I keep everything full of fresh fuel with sta-bil when sitting for long periods. IMO, fresh fuel is the keu. I'm convinced an empty carb is like having tools in an unheated garage. When conditions are right, moisture in the air will cause tools to rust, oxidation inside carbs. Only exception is my 4 cycle weedwacker which has a 2 cycle type carb. That said, I found it was about $50 to buy a carb, rebuild kit and shipping to replace the carb on weedwacker.

Good luck.
 
I have a generator with a Tecumseh engine that does the same thing if not run for a while. On mine, on the side of the carb under a cap that can be pried off is a brass jet with a screwdriver slot. Remove the jet & clean out the tiny holes in it with a fine wire or needle, etc. That stops mine from surging every time.
 

Typically, the mixture is a little lean which causes the governor to "hunt". Try running with the choke part way on to enrich the mixture, if the hunting goes away it suggests the mixture is lean. Also, many times connecting the generator to a load will clear the condition. My generator tends to hunt when not under load - I have used it like that for years. Lean is not necessarily bad, however it can interact with the governor.

If the carburator has adjustment screws you may be able to make a small adjustment. If it is a fixed jet carburator then disassembly is required to clean the metering jets.
 
Ny 3500 watt with a brigs engine does that when first started, after running about 5 minutes it smooths out. Last spring woulf not run, had in shop, bad carb, new one put on. Enough fuel to try it out, brought home and run for a half hour and shut off fuell and run dry. Later summer started and ran till dry. Past month put fuel in and started right off but that surging all the time but after it ran long enough to get good and warm up to operating temp it smoothed out. let run a while and shut off fuel and ran carb dry as per garage instructions. Probably should start again for a while.
 
check your gaskets on carb and manifold. you will surge also when gasket leaking. it changes your air to fuel ration. look for loose bolt.
 
Does it surge under load, or only with no load? If no load, keep the choke open a little till it warms up good. I had one doing that after gas in it got a few months old. Fresh gas, some Sea Foam and about an hours running solved the problem.

P.S. I am no fan of running carbs dry and letting the gaskets and diaphragms dry out. Checked with a couple friends that have small engine shops and they agreed with me.
 
I would say its running lean because of buildup in carb passages, fresh gas and some sea-foam should fix it, let it run awhile with some load on it.
 
I have a RV ready Champion 3500-4000 Watt generator that I had been VERY happy with. My machine has quite a few hours on it as we would take it to Country Stampede at Manhattan, KS and it would run many days straight with only one oil change and refueling every 10-12 hours. As I said it has been a very good machine for me. Then all of the sudden it started surging as you say. I'm pretty mechanical/electrical, so I take the carb apart, inspect and clean it and the intake gasket etc. I fire it back up same thing. I called Champion and they were very cooperative. They indicated since it was a fixed jet carburetor probably would be best to replace it so I order new carb and intake gasket. Low and behold that did not fix it either?? I figured I had nothing to lose so I clipped about 3/8 " off of the governor spring and hooked it all back up. Hmmm, no more surging. Now I know that the spring tension sets the engine speed therefore the 60Hz output frequency. So I get out my Fluke 87 multimeter and set it to measure frequency. I re-adjust the frequency to 60Hz and I've got good voltage, so voila it now works....Not sure why, only thing I can figure is the governor spring got a little week at that length. Pretty weird but I'm happy. PS the microwave clock in you RV is a good indicator of frequency over a period of time. Set the clock to match your cell phone then come back in 60 minutes and compare the microwave clock to the cell phone time. In a perfect world if your averaging 60 Hz on your generator the microwave should be within a minute of the cell phone. Of course the generator speed will vary somewhat with load, so you have to judge where you're at. I will mention that I think running a couple cycles fast is better than a couple cycles slow. Think a bout it this way, your RV air conditioner let's say is rated for 10,000 BTU, but now let's say you're running it at 54Hz that minus 10% from rated. This is not good for your AC but contemplate this. Your compressor is now running 10% slow and that's compounded by the fact that both the evaporator & condenser fans are running 10% slow too, so I'm thinking the 10,000 BTU AC unit is probably now well less than 10,000 BTU by more than 10%. I've rambled on long enough. Jim in Nebraska :wink:
 
The stronger the spring on the governor, the more sensitive the governor. If the governor has a different hole to install the spring which is closer to the pivot point on the opposite end of carburetor , try that. Other wise, weaken the spring and readjust speed for proper speed like poster below did. I'm not into generators so cannot tell you about the cycles etc but have had to do that on several small engines like riding mowers etc that are fixed jet carburetors.
 
Plugged idle circuit. Clear out all the passages with a fine, stiff wire. If you can't get it to run right, just cut your losses and replace the carb. Some of the newer carburetors are nearly impossible to get cleaned out once a passage is pluged.
 
Whip off the air filter , run the engine at mid to higher range rpm and spray a half a tin of carburettor cleaner into it over a few minutes . Alter the rpm from high to low as you do this .
 
Here is what I have found several times. Now-a lot of the replys are correct and check them but here is my fix. I ALWAYS run my gen-sets on Hi-Test gas. Also add a dash of Startron and some stabil. You will need to adjust the main jet just a tad to the leaner setting. With the unit running at 3600rpm and with a medium load on it you want to turn the main jet in a little at a time till you JUST see the throttle and govenor stop moving. You want it running rich to protect the valves. It should stay rock solid. I have had this trouble with three generators a Troy tiller and a log splitter. Gas is total garbage now so the hi-test fixes some of the trouble and the other stuff makes for even better. Last when you are done drain the gas and run the fuel out. I use eagle safety cans with the spring load lids and are kept in a good cool place. My two cents but it has worked for me.
 
Yep, the gas these days is crap. The idle circuits on small engines are so small even the smallest torch tip cleaner is too big. With such small jets, even a little varnish build up in a jet is enough to to change the ID of the jet which changes its tune.
Now throw in some ethanol and some deteriorated fuel components and it goes downhill quick.
 

I'm thinking of getting a propane fired 6000 watt inverter generator for back up incase of loss of line power.
 

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