StormCat 900 watt portable generator voltage adjustment

Harbor Freight’s StormCat 900 watt 63cc 2-cycle portable generator may periodically require voltage adjustment. This is especially important to check as the engine break-in procedure loosens up the engine. All of my StormCat generators have required slight adjustment at around 10-15 hours because the RPMs increased as the engine loosens up.

Luckily, this adjustment is easy to do, and requires only a screwdriver and a voltage meter (or Kill A Watt).



28 thoughts on “StormCat 900 watt portable generator voltage adjustment

  1. Does anyone have any idea on how to adjust the voltage on a Troy Built 5500 generator?? The voltage output on mine is 135V with no load and 133v with a load. That's too high for sensitive electronics. There is no AVR on the back of the generator and I have no idea where it's located. Whoever designed the carb on these B&S engines needs to be kicked. Every year the engine runs like crap after using it a few times. It has never run completely smooth since I bought it new. I have to keep the choke partially closed to make it run halfway decent. I even installed a fuel filter. I hear other people have the same problem. I took the carb off twice and cleaned it but it would start running like crap again within 2 months of cleaning it.

  2. Kev, I tried doing what you recommended. It was on the newer Harbor Freight 2 stroke generator. Before I adjusted it on a 'no load' basis, it read 120 volts and 62hz. I should have kept it there! Anyway, lesson learned. I brought it down to 60hz but the volts slipped to 85. I still love all your videos. David

  3. The instructions for the generator say's 120 v and 60 htz so the factory is not going to make sure it has the right settings because it's a china product.

  4. This generator should be used for nothing more then lights, and low grade electric devices. Never run sensitive electronics such as computers, and other things as this.

  5. This is a bad idea. mechanical governors have a 5% droop tolerance. Running at 62.5HZ and say 129VAC is perfectly normal. When under load the engine speed drops and voltage drops. Your save range is 108-132VAC and 58-63HZ, i mean ideally it should be 120VAC 60HZ but you cant always get that with a mechanical governor. The bigger 10k and and up machines employ an electronically assisted mechanical governor by use of a stepper motor. It monitors the speed and makes minor corrections where it keeps the 60hz within 1% instead of 5%. Anyone reading this since this machine has no AVR, set the engine speed to 62.5HZ and LEAVE IT ALONE!

  6. You're adjusting the engine RPM which directly affects the "frequency" of the AC generated which is measured in units of Hz. The change in voltage is coincidence and should not be considered to be adjustable by changing the engine RPM.

  7. You do not want to make this adjustment while the generator has no load. Mechanical governors will droop a few hz from no load to full load no matter if it's a little 900watt hf storm cat gen or a 350kw diesel industrial gen. Also Voltage should not be adjusted by changing the engine speed, to do this correctly you need to change the size of the capacitor in the excitation circuit.

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  9. I did that with my generator. I got it down to 60 Hz, but my voltage was reading 104. I'll have to tinker with it and find the middle ground. I really don't want to burn anything up. I only have 8 hours on my unit.

  10. Very useful video. I hope you don't mind but I'm sort of into these little generators. I put the waffle below on the good videos like yours just to help people across the pond. It's nice to see in the comments that no one is trying to burn it out straight out of the box.

    I have stripped both an old 650W and one of the new '900W'. The winding's are the same. It's the good old Chinese playing the numbers game. Next year they will be 950W or even 1000W. They run well at 500W. The main problem is 'inductive loads'. Light bulbs usually blow when you turn them on. The filament has a very low resistance when cold and the current they use is many times the normal just for that split second. These little generators will stand quite a bit but hang a 1000W saw on the end with a high inductive load (most motors do) and it'll be goodnight Vienna. There is a YouTube video somewhere of an elderly U.S. chap living out in the backwoods that's had one of these running for 6 hours every day for 5 years at 500W. He's got a 5A fuse in the line . Mine is 3 years old and I have a 2A fuse (UK – 250V) . I have blown the fuse but it could have been 'smelly' – that's what we call our little generator. There are more of these generators around the world with different names than makes of beer. They may have Harbor Freight on them but it might as well be Kiss Me Quick. 50:1 fuel oil is OK if it's not a hot day, if it is use 40:1. That's not on the American ones but is on ours. It's 30:1 while running in. Treat these little gens like an old wrinkly like me and they'll go forever.

    Come to think of it I don't know if the UK version has your adjustment screw. I'll have a look tomorrow.

  11. Thanks for posting this! As far as I can tell, voltage adjustment aside, this is the only YouTube video out there that shows how to adjust the idle on these little fussbuckets. As you probably know, there's no real idle adjustment screw on the carb. The owner's manual is not much help. Under "check/adjust idle speed" it just reads, "should be serviced by a qualified technician." Your video is the only hint I've ever seen that there's even an adjustment screw up in there. Somehow I just never noticed that access hole to it up above the pull start.

    I've got one of these that started idling way too low. I pulled the carb and really cleaned her out properly, thinking that might be the problem, but still, it'll just barely keep ticking over if you fuss around with the choke. I'm gonna fiddle with that adjustment screw you've pointed out when I get home tonight. I have a hunch it'll do the trick. Thanx again!

  12. I bought one Saturday and it was about 140 volts out of the box measured with a Fluke digital and Simpson 260 analog. As voltage and frequency are directly related on the small generators , a viberating reed meter showed way above 60 Hz. I did cut it back to about 124 volts. I will have to check it after I have ran it for more than the half hour or so that I have so far. The voltage does seem to hold constant under about a 250 watt load.

    I should looked for the video first as it took me a while to locate the adjusting screw.
    The screw head was also filled with some kind of 'tamper proof' material.

  13. How important is it to turn them down? I have never checked mine yet but I think I may. It's a different model but basically the same I think. Will it burn out quicker if not adjusted?

  14. I have 2 of these and found that when it goes up in load it does not keep the voltage or HZ . Both of mine do the same thing. I tested mine with a cheap harbor freight free meter and a fluke 77 . I wish there was a way to bring down the hunting on it .
    I am a disabled vet and use mine with a ups for my O/2 system.

  15. Easy-peasy! I'll check mine next time I have it running to see what it puts out. I have no Kill-A-Watt, but I do have a different wattmeter, but alas it doesn't read Hz, so I'll have to go by voltage.

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