Craftsman 5000 Watt Power Supply

[frankenstein]

Hi, folks! Nice forum! I've been reading up on these Craftsman/ Generac units, but I can't seem to find (understand) what I'm looking for. To start, I traded a small "King" 900 W generator (almost new) for a small gas water pump (which turned out to be seized), and a 5000W Sears generator (he said has a rebuilt engine and worked fine). Well, it turns out it's not working fine. Sure the engine runs great (except for the leaky carb), but the no- load voltage output is only 55 Volts on either 110V sockets, and the 230V socket gives out about 110V on the two "hot" lines. I don't know much about these generators, but I do know a lot about electrical/ electronic stuff. I just don't want to tear into this thing blind. Any help/ suggestions would be greatly apppreciated. thanks in advance, Dan

[frankenstein]

I forgot to give the model # of the Generac - 580 3189-6. (It's an oldy, hopefully a goody!)

[Fred M.]

I don't know if it is the same unit, but I found a generator at the Sears web site (Parts) using 580.31896, and 143.582072 for the engine.

You might check the brushes to be sure they are free and clean.

Also check engine speed. Running slow would cause voltage to be low. One way might be to connect two light bulbs in series between a 120 volt outlet on the generator and commercial power. As the frequency approaches 60 Hz, the change in intensity should slow down. With voltage low, they might not completely extinguish, but you should be able to see them pulse.

Fred

[frankenstein]

Are these unit supposed to run "full out" in order to obtain proper votage? This one semms to idle along @ 55V, but if I manually rev it up, I get real close to 110V. I know the carb has issues, so I will deal with them in the meantime.
thanks, Dan

[Tilinghast]

Frank,
I have a friend who has a small engine buisness and he works on generators too. He told me one time that some of the older generators put out there max watts at 1800 rpm and that most newer ones put out max watts at 3600 rpm if that is any help.
Dave.

[Jim Rankin]

the frequency of the AC voltage output is controlled by the number of poles on the generator and the rpm it's turning. To generate 60 hz power, many small generator sets turn 3600 rpm (2 pole generators), most common generators over about 10 KW turn 1800 rpm (4 pole gen), though a few oldies might turn 1200 (6 pole) and a few screamers might turn 3600 just depending on the engine and the use the set is intended for. When you get into large sizes, it is hard to generalize, but they may be even slower depending on the prime mover.

RPM also has a great deal to do with voltage output since it's the rate that the magnetic field cuts through the stator windings along with the strength of the field that makes the voltage.

[frankenstein]

When I get this ol' relic cranked up, it puts out the correct voltage, but it seems to run too hot, I am going to have the carb rebuilt, then see what happens. I finally got the "OFF" position to work on the control panel. (broken wire) Supposedly, the engine was rebuilt recently, so there shouldn't be carbon problems. (unless due to the carb) Oh well, one thing at a time. thanks

[Don Smith]

About what hp is the engine? If it is a single cylinder and around 8 hp it will be running at 3600 rpm to make the 120/240. You can verify this by peeking into the generator section and count the poles (windings) on the stationary field. Some contractor units also have an idle feature that allows it to run slower until it senses a load being applied. It then speeds up to the full speed and voltage. Usually there is an antomatic idle switch on the control panel. Plug in a saw and see if it picks up speed and voltage. Don Smith

[frankenstein]

There doesn't seem to be a setting for that idle down feature. There is a set screw on the side of the unit that turns the revs up and down. When I turn on a skill saw, you can see the linkage move to compensate. I believe it is working ok that way now, after I fiddled with the screw. (someone may have turned it down in the past) I think it runs too hot, though. But then again, the fuel tank was almost empty, so it may have gone too lean.

[John Newman, Jr.]

Check the clearance between the exhaust valve stem & the lifter. I've seen a few where the valve seat 'sinks' into the block taking out the clearance. If the exhaust valve isn't closing fully, it will run hot, the muffler will glow red and it will not have full power. Watch how you check it if the engine has a compression release for easy starting.
There should be a spring with (Hopefully...) adjustable tension that pulls the throttle open. The governor will try to close it. They balance at the proper RPM. If it runs too slow, you need more tension on the spring. Too fast, you need to back off the tension.

[Don Smith]

If it is running to hot and you think it might be too lean I would first try adjusting the mixture valve on the bottom of the carburator. Lean mixture sill make it not want to take an increase in output ac load smoothly. I am lazy, I always look for the easy things first. Don Smith