Craftsman Generac - Do I expect too much?

[Fred M.]

My twelve-year-old 3500 Watt Craftsman generator probably has a little over 100 hours total run time. I have changed the oil at intervals specified in the owners manual, so the GN-190 engine should not need any major service due to wear-out.

Recently I gained the ability to test the generator using various loads such as heaters and hotplates. Everything works great with a 2900 Watt load (117 Volts, 60 Hz). However the engine bogs down when an additional 500 Watt load is added, even though it is rated for 3500 Watts continuous/4375 Watts surge. When it bogs down, the throttle is wide open. With the 3400 Watt load, voltage is down to 90 and frequency down to 48 Hz.

Is this typical of such a generator, or should I expect it to meet the advertised specifications?

I have tried everything I can think of to improve it, including new spark plug, air filters, fresh gasoline, power control module and carburetor. So far nothing has made a significant difference.

The original carburetor had adjustable jets, but no overhaul kit was available. It was replaced with a fixed-jet carburetor five years ago. Another identical fixed-jet carburetor was recently obtained in a service kit for the GN-190, that included a new air filter gasket and air filter housing to match the carburetor's throat. Is it possible that the fixed-jet carburetor's design is responsible for the engine's lack of power?

Fred

[Franz©]

You can either look at it that you've now learned the engine is nearing the end of its service life, or you can look at it that you are another dissatisfied GeneCrap customer.

I've seen GeneCrap product for over 20 years, and in my opinion, you are a lucky owner. Most of their product didn't deliver as well as your machine. Have you tried running a compression test?

[Wayne 440]

I would say that is about all the unit was ever capable of. My experience with Generac indicates that the sales/marketing staff must have considerable influence on the wattage ratings. With Generac (and some other) units I have found 75 percent of the rated load to be a more realistic figure.

[armandh]

peak rated output from any engine is never easy.
everything from air pressure and temp. to fuel quality is in the question.
since there was a change of the carb I would have first suspected that the later has not enough capacity BUT since there never was a test on the earlier carb there is no way to determine that. some manufacturers just provide a little more margin some don't. given the rep. the pick of the litter may have done it under new and ideal conditions, you got the runt.

the POS hardware store lawn-more power that I have can be leaned out after an hour of operation and runs much better. it just wont start that way cold. [watch the throttle position while adjusting mixture] optimum mixture under operating load is ok only at that point.
BE SURE THE LINKAGE IS OPENING THE THROTTLE ALL THE WAY.

[armandh]

PS like any hot rodder try a bigger carb. that 500CFM holley 2 barel made the wife's 69 couger rhomp.

[Billy J Shafer]

With the Genajunk unit you have.You are doing good.

[ListerDiesel]

So many consumer items are sold with ratings that are little more than a licence to print money.

Hi-Fi with 'peak-power' ratings, while proper equipment was always rated at sine-wave output.

Horsepower on cars: we have US hp, UK hp, DIN hp, French 'CV' (Cheval-Vapeur) hp, SAE hp and so on.

Generators that are sold for the military have to undergo type testing to prove that they will give the rated loadings at the specified temperature range and fuel quality. Listers always give their rated hp to a British Standard, which normally means that it is good for that and a bit more besides.

I have no experience of the latest lightweight stuff that is being made in the far east and sold in the US and Europe, but it has already attracted criticism for its poor performance and build quality, so I guess you get what you pay for in the longer term.

Peter

[Patrick McNallen]

Expecting too much? Maybe, but maybe not. Are you sure that some of your electrical loads are not actually higher than you think? Also, the adulterated stuff they call "gasoline" today probably has less fuel value than what your older engine was rated with. Gasoline/methanol blends will not deliver the same power that good gasoline will. Another problem could be carbon deposits in the combustion chamber. If your replacement carburetor is smaller or jetted leaner than the original, it will likely reduce the engine's power. Alcohol/methanol belend "gasoline" will aggravate a lean-jetted condition. Your engine may benefit from a few hour's running at the highest load that it will carry and maintain voltage/frequency, using the best gasoline you can find with a little B-12 added to it. 100 hours isn't much run time in 12 years...

[Patrick McNallen]

One more thing: electric heaters and hot plates and similar appliances with resistive heating elements will draw much more amperage when they are cold. The hotter the elements get, the higher their electrical resistance and the less current they will draw. If you are running 2900 watts of resistive load on your Generac and throw on another 500 watt rated hot plate, the cold element in the added hot plate will likely draw a good deal more than its rating. This will bog the generator's already loaded engine, which will allow the other heating elements already on line to cool somewhat, which will increase their current draw too. This situation will act to keep the newly added load from ever fully coming up to operating temperature, and it will prevent the original loads from recovering to full operating temperature too. All this may well leave your generator with something more like a 4500 watt load, or even more to pull. If you were to add the last 500 watts of load by adding five 100 watt bulbs, one at a time, instead of say, a hot plate, the generator might well handle it.

[Fred M.]

Originally Posted by Patrick McNallen

Expecting too much? Maybe, but maybe not. Are you sure that some of your electrical loads are not actually higher than you think? Also, the adulterated stuff they call "gasoline" today probably has less fuel value than what your older engine was rated with.

Patrick-

I have a box with a voltmeter and frequency meter, that includes a wire loop for using a clamp-on ammeter. At 120 Volts, the load current is slightly high, but is slightly low at lower voltage. I'm fairly sure the loads are in the ballpark of their name-plate ratings. The digital meters are rated for better accuracy than is needed.

I'm not aware of any alcohol or methanol being in the local gas supply, but you never know. However, I have another cheapie generator that does deliver rated power with that same gasoline.

Franz's suggestion to do a compression check rings a bell. The Generac's 6.5 HP engine is somewhat easier to start than the other generator's 5.5 HP engine. Unfortunately my mechanic skills are limited to changing the spark plug and carburetor!

Armandh's suggestion to try a bigger carburetor sounds like a good idea. If I was sure the engine didn't have a compression or carbon deposit problem, I'd pursue that approach. I wonder if the next-larger Generac engine's carburetor would fit my machine?

Fred

[Jim Rankin]

If you are measuring amperage and using only resistive loads, you can calculate wattage, so your measurement exceeding rated amperage at 120V is indicating the true power load. Larger generators are usually rated at 80% power factor. (W/VA = 0.8) In that case, the engine is only rated to pull the kW amperage rating when loaded with a resistive load.

With a "normal" power factor load mix, generator kVA requirements and engine kW capability will max out at about the same time. Something with really poor power factor like a large under loaded motor may never load the engine, but exceed the amperage rating or exciter capability. A purely resistive load like your hot plates etc with PF=1.0 exceeds the engine kW rating before the generator amperage rating.

This is a good situation in a small set because it offers some protection of the generator end from damaging overload. The user hears the engine slowing down and notices the lights are dim, so he goes and unplugs something.

[Fred M.]

Originally Posted by Jim Rankin

The user hears the engine slowing down and notices the lights are dim, so he goes and unplugs something.

Jim-

This is exactly what happened after a storm last year. I tried to use a coffee maker while the refrigerator was running, and the engine sounded like it might stall. That is what started my attempts to analyze and improve the generator.

I suppose the only way I'll learn about engines is to tear into it. But it is an otherwise nice generator that I would hate to ruin. It ran most of its operating hours after a hurricane two years ago, and should be able to do the same again. Next time I'll unplug the refrigerator when making coffee.

I posted here hoping to get some assurance that the generator and engine design was capable of delivering full power. If the response had been more positive, I would have taken it to a local repair shop that has the capability to do compression checks, et cetera. Now I think I'll keep it the way it is. I had no idea Generac had such a poor reputation!

Fred

[Jim Rankin]

Fred,
If it isn't using excessive amounts of oil, producing a lot of blue smoke, knocking, backfiring etc. the basic engine may be fine. However things like valve adjustments and carburetor adjustments can have a dramatic effect on the performance of an engine especially one with one cylinder. On a multicylinder engine it can be hard to determine which cylinder is completely dead, but on yours, if there's a little problem, you know it. Carbon in the cylinder ups the compression, maybe partially making up for wear etc. Carbon in the exhaust port and muffler may restrict flow enough to cause problems. Always, the air filter, fuel filter and spark plug are the most likely to be the problem and the cheapest things to try. Then you can branch out into adjustments etc.

If you want to learn about it, I would suggest going back to the original carburetor if it's available. Carefully disassemble it and clean with carburetor cleaner. Clean all passages and drilled jets with compressed air, carburetor cleaner and something like a plastic broom straw or fine copper wire so you don't ream them out and enlarge the hole. Any adjustment like a needle valve can be gently screwed in until it bottoms out, counting and recording the turns before you remove it for cleaning, so you can replace it at the original setting when you reassemble it. If they have all been messed with before, usually start with the adjustments about 1 to 2 turns open from fully screwed in. If you decide to mount the old carburetor, make sure there are no leaks on the gasket where it bolts up.

When adjusting it, get it where it will run by experimenting and then load it with whatever load it will carry. While it is running, adjust the load or high speed adjustment while watching the throttle lever. When you improve the mixture, the throttle will close a little (or a lot)under the steady load. If you are going the wrong way with your adjustments, the throttle will open wider and the engine may begin missing, smoking etc. if it is bad enough.

Within a range of adjustment that seems to make no change, go toward rich a little and then add a significant chunk of load suddenly. If you are too rich, it will usually bog down before recovering and produce a lot of black smoke. If you are too lean or fuel is restricted somewhere, the exhaust will stay clear and the engine will loose speed when you add the load and not recover. You want to adjust it so it doesn't bog down much or at all under a sudden load increase and will carry the maximum load without smoke and plug fouling problems.

Have fun.

[Fred M.]

Jim-

Your carburetor adjustment procedure is a bit more detailed than the one in the Craftsman owner's manual, but is in agreement.

When the fixed-jet carb did not improve the problem, I dug out the old one. After cleaning lots of crud from around the high-speed jet, I got it to a point where it appeared to work as well as the fixed-jet carb, but no better. The idle jet will adjust per the manual but the high-speed jet never reaches the point where it improves performance under load or causes smoke. I think there is still a lot of crud to clean out, especially in other nooks and crannys where I didn't clean before.

I have replaced the spark plug and air filters with no improvement. The old plug looked almost new. I think it had been changed once before, but that was before it ran for around 100 hours a couple years ago.

The in-tank fuel filter was changed when I replaced the fuel shut-off valve last year, but I had not run load tests prior to that time. However the gas flow is quite good when draining the tank using a 1/4 inch fuel line.

Thanks for the encouragement.

Fred

[Jim Rankin]

Sometimes it is necessary to drill out soft drive-in plugs to get a straight shot cleaning out drilled passages through the carburetor. Maybe use a lead shot to plug the hole? Or you could attempt to thread a wire down the main jet from either end to make sure there's nothing obstructing it. If absoulutely clean, then you could investigate finding a drill the next size larger and enlarging the passageway or jet whichever is smaller. Drills are available in incremental sizes (by letter??) which can be used for such precision drilling.

[John Newman, Jr.]

Fred,
You mentioned that your engine has an in tank fuel filter. Is this just a fine screen on the petcock? If so, I would get a gereric fuel filter from an auto parts store and install it in the line just before the carb. With the size of the jets in these little carbs, it doesn't take much to clog them and an additional layer of filteration is good insurance.

[Raymond]

What engine do you have? Generac doesn't manufacture anything, they just cobble together the cheapest stuff they can find. You may have to pull the head and measure the bore and stroke. If you dont have at least 16 cubic inches you will never see 3500 watts output.

[Fred M.]

Raymond-

The engine is the Generac-Nagano GN-190, rated at 6.5 HP. According to the manual, the 190 refers to 190 cubic centimeters, which is 11.6 cubic inches if I did the math right. I wonder if Generac weasel-worded the specs? The generator part might easily put out 3500 watts if the engine part could drive it!

Jim -

I took the old carburetor apart. I used some Gunk Carburetor spray-cleaner on all its openings, and liquid squirted freely out of many unexpected places. I used compressed air to dry it out. I soaked the small parts, and then had to scrape the goo off of the high-speed jet. I now believe the original problem with that carb was just the goo around the high-speed jet, which is located near the bottom of the bowl. Apparently the residual fuel evaporated too many times from being left unused for months at a time. It certainly didn't get clogged by being run too much!

I have recently taken to turning off the fuel valve and running the engine until it quits, choking it to burn the last bit of gas. Even so, I find there is still a little gas in the carburetor when taking it apart.

Today I installed the old adjustable-jet carburetor and attempted to adjust it. By watching the throttle, I found a very narrow range where there was a peak in the high speed jet adjustment with 3400 watts load. It now is up to about 54 Hz and 105 Volts, which is a bit better than with the new carb. It does falter when a load is first applied, but picks up OK.

Fred

[Patrick McNallen]

It sounds like you are on top of the problem. Setting your main jet just slightly richer may improve the throttle response, and sometimes setting the plug gap a couple of thousandths tighter will help. The slight hesitation could be related to methanol-adulterated gasoline. If the engine doesn't backfire or and stumble badly when the load is increased suddenly, it's probably OK. I suspect that most lightweight single-cylinder generator sets would tend to pull down a little before picking up a sudden load increase, especially if the engine is not fully warmed up. Also, if you are located much above sea-level, your engine will deliver a little less than full power. I think that there is a rule of thumb to determine power loss due to elevation, but I don't have the figures. It may be on the order of 2 or 3 % per 1,000 feet above sea level.

[Zeromedic]

Originally Posted by Fred M.

Raymond-

It now is up to about 54 Hz and 105 Volts, which is a bit better than with the new carb. It does falter when a load is first applied, but picks up OK.

Fred

Your governor seems mis-adjusted. Look for a nut on a threaded
shaft straight above the recoil start. Best tool is a hollow shaft nut
driver. clockwise raises rpm. shoot for 62 Hz no load.

Also check that you have the throttle actuator wire in the correct
hole on the carb linkage, you want the hole closest to the block, and
the little pita damper spring should be in the same hole.

And if all the Gene"crap" bashers have gone to bed ...

agreed, lots of crap has been sold with Generac labels, any gen-head
powered by Briggs or Coleman flathead engines.

A few old boys in Wisconsin have also been crankin out some very
fine GN/GH engines for almost 20 years now. Overhead valve,
pressure lube(oil pump), usually with external filter, well balanced.
Not quite Honda quality, but damn close.

Alas, Generac has been bought by Briggs, and they didn't
get the rights to the GN (Generac-Nagano) design. It lives on in
the Generac (not BS) home standby units, all propane or ng.

Steve