Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Hi guys. I have tried getting to the root of this problem via other forums without luck.  After doing some searching, I was able to track down this forum, it's great!  I have a problem with my Honda EX350 generator. Here's some information regarding this unit in case you haven't seen one before. It is powered by a small two stroke engine mixed at a 100:1 ratio. The carburetor is mounted to the bottom of the crankcase and uses a single metal reed valve. The igniton is a solid state design. Because the generator is of an inverter design (much like the newer Honda generators), the engine does not have to run at 3600 rpm. There is a low rpm position (150 watts) and a high rpm position (300 watts). Here is the problem.

When in the high rpm position under full load (300 watts), after almost exactly 2 minutes of running, the thing bogs down for about 6-7 seconds (just like you were putting the choke on), then goes back up to normal rpm. This goes on until it runs out of gas, like clockwork, every two minutes. I cannot figure out what is causing this. I have checked absolutely everything and have come up with nothing. I have a friend who owns the same unit, and after spending hours troubleshooting my generator and finding nothing, I was forced to simply change parts to see if I could find the problem. Here is what was changed.

air filter, carburetor, reed valve, spark plug, exhaust, gas cap (vented)

None of this fixed the problem. The thing is, the engine starts first pull every time and runs at a steady rpm.  The engine just seems to be loading up and just bogs down for a few seconds, then it seems to clear itself up.

Here's the thing, partially blocking the air intake with my thumb causes the engine to run the exact same way until I remove my thumb. But when the engine experiences the problem by itself, it only happens every two minutes.

Does anyone have any ideas what might be the problem, I am out of ideas.

Same deal with the gas cap removed.  Spark plug looks great, golden brown.  I have brought it to a dealer, but they haven't been able to find anything either.   It's not their fault as this is a very odd problem.  Thanks again.

Just had a thought guys.  Is it possible the flywheel key could be slightly sheared?  Maybe not enough to make a significant difference under light or no load, but enough to get the engine to bog down after a few minutes of full load operation.  Then again, a sheared flywheel key usually affects operation regardless of load.  Just an idea...

I'm stumped.

Let me ask this.....when it bogs down, does it bog down to about the same point as when it runs in the low RPM mode?

in your origional posts you said "There is a low rpm position (150 watts) and a high rpm position (300 watts)" and that on the low wattage setting it runs fine. Have you tried connecting a lower wattage load, say 150 watts, with the generator set oh the high wattage setting? if the same problem exists on the high setting with a half load of 150 watts but on the low wattage setting things are fine, then that would indicate to me, its an internal problem in the gen. set itself. its very possible one of the components has a minute crack in the insulation (on the high wattage setting) and is opening up causing a leak or partial short to ground, causing the generator to create its own overload.

(i had this happen once on an electronic motor controller, the insulation on a current limiting resistor was cracked on the back side & as it warmed up the motor would cease to run, & what a b**** to find)

going back to basics though, double check your lamp(s) that you are not running more than 300 watts, a halogen work lamp for example, 300 and 500 watt lamps look identical. is it possible the bulb itself is a higher wattage than the gen. is rated at??

Hi Bill:

Well, here is my 2 cents worth.  Does this carburator have a mixture adjustment?  It kind of sounds to me that the unit is slightly out of wack and is acting up out of a bad setting.  Also, what about a governor?  Perhaps this might be slightly out of wack?

bbwb

spottedpony wrote:
Hmmm...  I believe I had previously posted that at the high setting with less than 300 watts load, the generator ran fine.  I was wrong.  I tested the generator on high with 3- 60W bulbs, and I got the same result, bogging at approx 2 minute intervals.  The odd thing is that with the 3- 60W bulbs, the bogging is not nearly as severe, but still there at the same intervals.  With the 300 watt load, the bogging is very severe. 

The bulb is definitely a 300 watt.  I have tried the same exact lamp on a different EX 350 with no problem whatsoever.

Man, I am about ready to throw this thing into the river...

It also sounds like your basic engine surge or hunting.  I don't know how easy it is to get to the governor linkage, but when it starts to surge or bog, see if you can hold the linkage steady to see if the engine smooths out.  If it still bogs or hunts, you may have a carb issue or the engine may have to be opened up and have the internal components of the governor checked.   

I'm thinking you have an electrical problem if it bogs down at the same regular interval with two different loads.  Hard to imagine a fuel related problem doing that.   Perhaps there's an electrical overload sensor that can shut down the ignition when it detects an overload.  This sensor could be defective.  You did say the overload light comes on when you have the problem.  Alternatively the electronic ignition module could have an intermittant failure.  Is the symptom the same if you push the shutdown switch for a second or so?   -Bob

It may seem im rambling a bit here but bear with me, some of this may shed a little more light on the subject, or at least get others thinking outside the box so to speak, for other solutions. Years ago, i built a small (12 volt) generator with a 3 or 3 1/2 hp briggs and a 60 amp alternator to use in our motor home for the times i didnt need to run the big onan gen. set.(man was that thing fuel hungry) My goal here was something small, but addiquate to keep the accessory batteries charged when we were somewhere 120/240 volt "household current" wasnt available. To make a long story short, it worked great, but on the first attempt with that alternator hooked to the engine you couldnt start ti, & the solution was to put a switch in the alternator field wire between the alt. and the voltage regulater to disconnect the load until the briggs was running, then it started fine & that little gen. worked like a champ, but you could sure tell when it was working hard, it would really make that litlte briggs work when a heavy charging load was put on it.

 after thinking about this, again,  im leaning  towards it being a faulty component in the gen head itself, or perhaps nothing more than a chaffed wire, that with vibration periodicly vibrates against the metal case causing an overload and pulling the motor down.

I would still do a voltage check on the generator when your problem occurs as this would be a good indication of the gen. being overloaded, & it might help track the problem down.& keep in mind, as voltage drops, wattage or amperage demands from an appliance increase. As a master electrician, ive delt many times with similar problems, due to overloading a panel or voltage from a transformer being low. Generally speaking, its acceptable to have +/- 10 percent of an optimal 120 volts.or anywhere from 108 to 132 volts when supplying lights or appliances however as previously mentioned, as volts drop, wattage demands increase, so its entirely possible that if the volt output of the gen. is low, by 10 percent, the wattage demand by your connected load has increased enough to effectively overload the generator.

im at a loss for any other thoiughts on the problem, but as discussed by several, im confident its a problem in the gen. head itself. Have you contacted honda directly to see what they're suggestions are?

I'm starting to think it's in the inverter unit also.  Honda doesn't want to hear about a model that has been discontinued for over five years, they'd rather talk about the current stuff.  I can't blame them.

Oh how I wish I could make some kind of recording so you guys could hear exactly what I mean.  It really is an odd problem that I have never seen on any engine of any type.