Honda GX390 120 Volt RV Generator

[Henry W]

The next step is to instal an electrical enclosure for the capacitor's and buss-bar where the generator will be wired. There will be a 30 amp RV breaker box that will tie into this enclosure.

[Henry W]

I felt the test the other day was not as accurate as it should of been so I decided to do another.
The Makita heat gun used on the test was constantly switching on&off and in turn, true readings were impossible to record.

For this recent test the equipment used to load up the generator were:
2——1500 watt rated space heaters
1—— CFC vacuum pump.
1—— Delta sawdust/wood chip vacuum

With no load the readings read 129.4 volts at 63.79 hertz.

With a 31 amp load the readings read 116.7 volts at 59.79 hertz, engine speed was 2588 rpm.
(Readings were taken after an hour of continuous run time loaded at 31 amps.)

I feel the readings turned out to be more accurate on this test.

I met the goal of reaching 3600 watts continuous output with a good surge rating.

I'm curious on the fuel consumption on a 3600 watt load. More testing soon.

[veggie]

That's an interesting generator head. Have not seen one like that before.
What type is it again ?

[Henry W]

The generator head is a Mecc alte SA20-130/2 APU generator head.
8.4 kVA - 3600 RPM
120/240 Volt, Single phase, 60 Hz.

There is not much info on these for the public. They were designed for specific OEM's such as Thermo-King, Carrier and a few others.

Here is some info:
https://www.meccalte.com/downloads/SA20.pdf

[veggie]

Thanks hwew,
It's a nice little compact gen head.

I would like to play with one of those pancake alternators like you had on your Kubota 2cyl.
Unfortunately they are very expensive and hard to find in Canada.
I had an idea of putting one on the shaft of my Lister. I think they make power at low speed, although greatly reduced power.

[Henry W]

Did some testing on the generator this afternoon and I've been noticing a good amount of vibration resting my hand on the engine. At first I thought the 7" pulley was out of balance. But, when I increased or reduced the RPM's on the engine by a couple hundred RPM's higher or lower the vibration would reduce considerably. I took the pulley off and ran the engine again and nothing changed. This engine has all the classic symptoms of critical speed phenomenon at the speed I've chosen to run it. Honda also has a write-up about this In their tech manual and says to watch out for it at certain speeds and make adjustments as necessary. So, where does this leave me? The engine speed/output was enough to meet my needs where it was set. So, I will have to go up in RPM's. I'll be setting it up to run it at 2950-3050 RPM's and than test it again.

Henry

[veggie]

How are the noise levels on the Honda GX?
Are they acceptable for your application?

[Henry W]

It's been a while, just got done setting up the genset to run at around 3000 rpm's. The belt will be in tomorrow.

Veggie, the noise levels are ok. They will be better when the enclosure is made.

I hope I'm able to do test runs tomorrow.

[Henry W]

Ran tests of the genset. Here are the results. With a 1200 watt load running at 3060 rpm the engine stalled. It just burned through over a gallon of fuel in just over an hour.   Sitting here puzzled how this could happen? Bob G suggested to measure 32 oz. of gas and and do another test run with the belt off the engine. Well, it ran for 21-22 minutes with no load.

It did not use this much before when running around 2700 rpm.

Here are the fuel consumption specs. under rated load. Honda GX390 uses .977 gal/hr @3600 rpm with an approximate run time of 1.8 hrs. per tank.

Today we think we solved the mystery. The engine had a bad vibration problem from 2600 - 2800 rpm. So this was the reason I changed pulleys to run it near 3000 rpm's. We think the vibration frequency near 3000 rpm caused the float needle valve not to seat properly and in turn gas more gas was being drawn in the carburetor and in turn caused a rich run condition. The spark arrester screen was covered in heavy soot. This GX390 had such bad vibration that when putting a hand on while running it the vibration hurt and causing some numbness.

What is going on with this project.
I brought the engine back and got a complete refund.
I purchased a GX240 and will be mounting it in the morning and continue testing again.
Will start over by running it at 2700 rpm and see how it does. Than run another test at 3000 rpm.
If the vibration is considerably less I will continue with the build. If the vibration is the same as before. I might have to change the design.

The reason I decided to try the GX240 is less rotating  mass.
*Smaller, lighter piston
*Shorter, lighter connecting rod
*Lighter crank with shorter stroke
*Slightly higher compression
Hopefully the  lighter rotating mass might reduce the vibration considerably.

More later.

[Henry W]

Hooked up the GX240 and test ran it.
The results are as follows:
Ran much smoother but the engine surges bad. Did tests by heating it up good and no change. Next test was recommended by our fearless leader. Started the engine and closed the choke slowly to see it it stops the surging. Well, it worked!

I went on the internet and found the the Honda GX240 has surging issues. It is the way the carb is set up in the idle circuit. And this is non adjustable. I can't blame Honda. I blame our EPA. Do they understand that an engine that constantly surges will use more fuel than one that operates properly with the correct fuel mixture. All engine manufacturers are going through the same issues. The only way I see getting around this is pull the carb off, throw it out and install an after market fuel injection system.
But I'm at the point that I'm ready to abandon the gas engine.
Back to the drawing board.

So, I returned the engine.

PS, I just thought of something. What would of worked is rip the carb off, throw it out and replace it with a good Marvel-Schebler VH-12 carb from the 40's & 50's. But that modification would void the warranty.

Added:
Here is the carb I used on a Bolens 800 garden tractor with a Wisconsin S7D engine.
https://partmartusa.com/products/vh-12-carburetor-vh12-marvel-schebler-wisconsin-new-old-stock

[Tom Reed]

Hooked up the GX240 and test ran it.
The results are as follows:
Ran much smoother but the engine surges bad. Did tests by heating it up good and no change. Next test was recommended by our fearless leader. Started the engine and closed the choke slowly to see it it stops the surging. Well, it worked!

I went on the internet and found the the Honda GX240 has surging issues. It is the way the carb is set up in the idle circuit. And this is non adjustable. I can't blame Honda. I blame our EPA. Do they understand that an engine that constantly surges will use more fuel than one that operates properly with the correct fuel mixture. All engine manufacturers are going through the same issues. The only way I see getting around this is pull the carb off, throw it out and install an after market fuel injection system.
But I'm at the point that I'm ready to abandon the gas engine and look for a good diesel.
Back to the drawing board.

So, I returned the engine.

PS, I just thought of something. What would of worked is rip that piece of §#¥% carb off, throw it out and replace it with a good Marvel-Schebler carb from the 40's & 50's. They are some of the best carbs period. I've seen how one worked. But that modification would void the warranty.

Added:
Here is the carb I used.
https://partmartusa.com/products/vh-12-carburetor-vh12-marvel-schebler-wisconsin-new-old-stock

Another option is to drill the jet to richen it up a bit.

[Henry W]

I thought of it.... People say the idle circuit is non adjustable and you can't get to the holes to richen it up. The engine is gone. I returned it. I'm going to take some time and think about it. I would like to have the flexibility of adjusting the fuel mixture without taking the carb apart. And as we all know that ability has been taken away from us. So, when an RVer camps out 8000 feet in elevation the carb has to be taken apart and rejetted. And than do it over again once down to 3000 or below. How stupid is that? If someone wants an engine to run right at different elevations the carb should be adjustable on the fly. Spare the time of having to take it apart all the time. The EPA should of allowed RV generators to be exempt from this issue.

[mobile_bob]

Henry

check your email in re to the air cooled diesel engine

bob g

[Henry W]

Dr. G, your a genius!!!

You solved the problem!

I know what I'll be doing now.

Skunk Works is back in business!!!

[mobile_bob]

i am flattered, however i am no genius

just a poor boy that has had to live outside the box in order to afford to get done what i want done.

i wouldn't have a clue what it would be like to simply put down a pile of cash for a ready made solution to a problem.