How To Adjust The RPM On A Honda GX390 Generator Engine 

You can also plug a frequency meter into one of the power outlets and adjust the engine speed for a reading of 60 hertz (USA line frequency 60 cycles/ second = 3600 cycles/ minute hence 3600 engine RPM). Some generators have a frequency meter built in or you can use a device like a P3International Kil-A-Watt available from many sources. I like to adjust my generator for 60 Hz while the generator is supplying about a 50% load. As the load increases, the frequency will decrease a bit as the engine slows down and as the load lightens, the frequency will increase. My generator does not have closed loop frequency control, so setting the line frequency (engine speed) with a typical load is a reasonable compromise.

I have a Honda gx390 motor with a comet zwd4040 4000 psi pump on it. When I pull the pressure wand trigger, the rpm is normal, but when I let go of the trigger the rpm goes way up. What do you think I should do? Will the rpm screw work on the pressure washer?

For those performing this you will want to check this under load as well. I like to use a 1500W heater as load and adjust accordingly. That way you know you frequency and voltage are in line under load.

Excellent, as always! That screw was really way out, I'm thinking vibration over the course of the generator's use had it unscrew, unless it was that far out of adjustment from the factory, which I tend to doubt.

Just a note to add, 3600 = 60 Revolutions per second which is where 60Hz frequency comes from for your power. If you have more or less RPM your power output frequency will be more or less. Europe uses 50Hz and the US uses 60Hz. I'm sure other Countries us some variation of the two as well because appliances are designed for either, or, or both.

I have about the same generator and adjust engine speed with it under load,, a couple 500 watt halogen lights work well for this. Bought one of those 20 buck tach/time gauges ...simple surface mount... makes keepin up with 60 hz easy and hours on motor for oil changes

Can I use a multimeter that measures Hertz instead.

I just got a 6000W sungold power inverter that I intended to use as overnight backup to my Honda Northstar brushless generator, but it refuses to qualify the generator power and switch the input side to the output. It instead remains on battery inverter mode and the status display says "AC ABNORMAL 238V" on the input side. The generator frequency is 62Hz. My APC UPSes don't have a problem with it, but the sungold absolutely refuses to qualify it. I'm going to try adjusting the engine speed, but I fear that under load it will drop below 60Hz and the inverter will go to battery again.

Thank you, this was exactly the information I needed and very clearly presented.

You have any idea what your Idle control ON RPM's are or what they typically should be? I have an old Campbel-Hausfeld GN654800AC with a GX390 and I can't find a manual for it or settings. It runs fine and outputs 60hz @ 120V @ 3600RPM, I just want to make sure the Idle control RPM's are at a typical range (i think it was 2660RPM when ON). The idle control has a magnetic coil that can be adjusted around a bit to effect those RPM's. Adjust it too much and it will start revving up over and over.

I just bought the EX Tack Plus like you have in the video. I also have the same Honda GX390 engine on my generator. Did the readings on your tack jump all over the place. It seems you have a steady readout. The one I have right out of the box, the readings are all over the place (2,473 rpm to 3898rpm) I have an analog wireless tack that reads steady at about 3800 which is about right for a miller generator. I noticed that your reading was steady at 3600rpm. Maybe I got a bad meter. No way I can adjust accurately with readings jumping all over. I used the setting 2:1 with the cable and wireless same results.

Have a Honda hour meter tach on my EM5000 generator with a propane kit. The propane connects to the intake line pre carb and I measure 3640-3680. line freq = approx 57 hz. Given that I am running propane and I have tweaked the propane delivery valve to produce the highest RPM will your carb adjustment work?

There is a link in the description to where I bought the tach in this video

How about a Honda EU3000IS inverter generator that rhe rpms are too low. ..how is that adjusted?

shouldn't you set rpms when the engine is under load? Or does it make no difference?

Thanks for the info on the Tach. Have a great weekend Don.

I have a gx240 with the same configuration and with new carburetor only runs on choke and is surging, when spray ether by vacuum plate it runs correctly is it possible vacuum plate is bad ?

First off: That looks awfully Chinese-made to me....or are the Chinese cloning better these days? Anyway; You failed to mention just how the governor works or even the effect of the plastic throttle stop screw on the carb. Also, the revs will be affected by the setting of the air/fuel mixture screw....a metal screw on the side of the carb. (Be guided by the plug colour). The idea of the governor is to speed UP the engine when a heavy electrial load is placed upon it.....it then throttles back as the load is catered for, that is, as the running amps diminish..... It is the shock of the heavy amperage start up, that the generator tries to cope with. ( A heavy duty 9" angle grinder for example.) What should happen is as the revs fall, the windage on the governor (Within the generator) is decreased & that causes the lever to pull the throttle open...when the windage returns to its normal level...ie the revs have now increased...it SLOWS the engine & maintains the RPM at the correct voltage. (The higher the RPM....The higher the voltage [& Hz incidentally.) The same Governing action is used on Briggs & Stratton engines...lawnmowers, for example....You hit a patch of, say, damp grass & the load on the blades is increased...the revs fall....the windage falls & the thottle is pulled open to increase the revs & thereby the energy to cut the wet grass or whatever.....before the engine stalls. Sounds so simple! Yet can& does go wrong. HEY!!!! Not trying to be clever here...or criticize the poster.....but there is somewhat more to getting the revs right than that one single screw...... I have a similar generator in at the moment: It runs perfectly well at 220v/50Hz (South America) but when faced with a shock load, the RPM & voltage falls & the governor is not compensating for it by increasing the revs.....as the grinder runs, the current demand falls & the Genny revs return to normal....... But then, load the Grinder with some actual work, which increases the amperage load.... & you find your self in a vicious circle..... I came here looking for a solution but the nearest I could find was this example....and sadly, it does not really help. I'm sure someone out there will say: "Ha...this is what you do.....!" (BE AWARE: With some clones of the HONDA ENGINE.... Running them at maximum speed can cause self-destruction of the engine.....Seriously. What happens is that the magnet ON the flywheel (that provides the ignition spark) can become "displaced" & rips the induction coil off its aluminium mountings. I've had two machines in, that lost that permanent magnet off the flywheel: One I salvaged with a new Flywheel...[not cheap either.] The other demolished the Coil Mounting lugs....Engine is scrap...... What some clever clogs did, was manually hold the throttle wide open when switching on the massive electrical load which was stalling the engine....A BIG NO-NO!..))

glad to see a generator video.im not that familiar with generators,would love to see some more.

Thank's Dony, I like your video's I've l;earned a loy

Hi donyboy73 I know you have lots of work at the moment but could you show a video of how the tach actually works thanks

were do you order your parts from

My rpm screw is stripped any suggestions

I have a Subaru generator with a Robin engine. The intake air filter (279-32612-08) is deteriorated, a simple air filter is $25. Any alternative suggestions ?

What if the RPMs are good but the engine doesn't idle down or rev up on a load

I love his videos they are good

my genorator has a gx390 and it runs at 2000 rom's. that is what themanufacturer reccommends and it pumps out 130 volts. i really like it, it is nice and quiet. the arc welder with the same engine runs at 4k rpm's and it is really loud, you can't hear the weld so it is really hard to weld with it

Can you check the RPM on a honda ex-5000 with the old type auto style tachometer, that has two wire clamps? Where would you connect the clamps on the generator? I am a new subscriber, THANKS FRIEND.

I can watch this stuff all day! Another great video!

Thanks great video. I needed to clean carb but seen they were cheep so I just replaced it. It started easy but the RPMs are way to fast now. Looks like the gov linkage isn't moving over to slow it down unless I hold it over by hand. Is this what I should adjust for this or do I need to look into the gov?? Thanks It worked fine the last time I ran it.

Great tip. Thank you. Could you show or tell me how you would adjust a the rpm's on a honda EU6500IS inverter generator. And what the rpm's should be at with Eco off snd on.

Looks like it was 9 years ago but thank you so much for doing this! Really helped on a similar generator I bought 12 years ago :)

hi Dony ,, do u know what is the purpose of the other adjustable metal screw on the carburetor ?

Hi I am from P.R. after hurricane Maria I adjust my generator by Hz not RPMs put it at 58hz the engine runs more quiet, more gas eficient and the oil last a week.

Honda clones redline at 3600 yet mine has seized up t 3000 rpms. Pulled the head and no damage, cross hatches are perfect. Will not turn by rope or starter. Think a bearing spun?

Same thing with lawn mower engines: always consult the OEM involved for the correct speed setting applicable to the engine model used.

Do you have any info on the auto throttle that you can send my? Thanks, I had to repair a generator today and the auto throttle was giving problems.

donyboy, I'm wondering if you did other checks, like air filter/spark plug/fuel/fuel bowel ? Just to make sure.

busco problemas acelerado de mi planta honda es 6500

Thx for the Vid Donny. I have a question regarding how/where you obtained your tach reading from. I purchased a digital tach myself but a different brand name. So my question is, what are you pointing the laser at to get your RPM reading?

thanks for that , just what the small engine doctor ordered :)

Can you please tell me how to increase the rpm on my 20 hp honda zero turn. It seems low. Is it the same process?

What reader did you use to measure the rpms? Where dis did you point the reader to take the measurement?

Thanks!

Donboy always delivers :D

I have a generator with the GX390 engine. when I run it and have something running off from it, it surges. The only way to stop the surging is to pull the choke out about half way. What can I do to stop the surging?

What battery can we use to start the genarator

Sir i have petrol generator LONSIN china made , i am facing jerks in its race while running. what will be the cause of this fault?

Does anyone know the valve lash spec for a Honda hs521 snow blower?

Donyboy - I had one of these generators and the gas tank was so corroded, it looked like they ran red mud in it. I let vinegar sit in it and some sea foam and gas. Plus took a flexible magnet tied rags to the end and cleaned inside with about 40 rags. It was pretty clean unless you let fuel sit in it, it would clog back up. It was hard to even get all the gas out of the top and bottom holes Is there a good way to clean one of these tanks out?

Great video

How much for a Tach like that in US currency?

my fans are running very slowly on generators.what should i do? move the rpm screw on left or right?

Awsome video Don! Is that tachometer new? Never saw it in your previous videos... Have yourself a great weekend :)

Thank you for the information it was had to find.

I have a generator with the same honda motor. I have to keep the choke pulled out at all times or the motor dies. Do you have a suggestion on whats wrong?

Just a quick thank you young man for such clear vids and easy directions. Effectively have my generators purring like kittens. It seems regardless the issue, you have a vid with the fix,,,, saving me time and $$. Keep it up.

Always the best.

this maybe a dumb question, but would it not be better for the motor if they had the motor running at 1800 rpm with a gear ratio to run the generator part at 3600rpm ..... seems like it would be alot quieter and better for the motor if they designed it this way ?? Im sure they dont want motors to run for 30-40 yrs like the old briggs flatheads could ...... or have I over thought this ?

Will this apply to a Generac 7500 watt generator

Excellent. Your channel is simply the most informative around. Thank you.

Model # an make of tachometer Doc please ? TU

Thanks donboy73! really easy to understand. subscribed

Good job Donny! Have a good weekend.

thanks for the vid, bro!

thanks

You just wanted to show us your new toy didn't you ;-)

Thanks!

Where'd you get the tool for checking RPM???

where did you get your tachometer from?

Muy indispensable dany, regularle las revoluciones a 3600 de lo confrario no levantaria el voltaje que deve de ser saludos y felicidades por tu pagina

What was that tool called that you used to check the RPM

Hey don where did you get your tachometer from thanks

keeep theeem coming man

Which engine part tell RPM when you use tachometer? I mean tachometer laser read which part of engine?