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Discussion Starter · #1 ·
Hi all. New here.

I have a Chinese 5kVA open-frame generator with a GX390 clone engine.

I just replaced the carb with a tri-fuel replacement and it runs fine on gasoline. But when I switched to propane/LPG, it ran a little rough at first. I loosened the fuel screw (yellow arrow in the pic below) to richen up the fuel mix and now it seems to run fine. All tests so far were done without a load.

My question; Is there a proper or detailed procedure to adjust this screw? Do I need to do it with/without a load? How far back should I loosen the screw AFTER the engine starts to run smooth?

Thank you!

 

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pretty simple
make sure it is out of gasoline first by removing power to the sol on the bottom of the bowl during run on gasoline.

if the carb is in question for the gen at first run set up;
adjust with no load first.
we use space heaters when field setting the demand regulator load block flow.
then start adding load noting where you have to adjust the screw to make it run right.
and final is at the rated load of the gen set.
then check it at no load.

if the carb is matched right to the gen set.
we go right in to full load and do the right to lean and set it at the middle then check it at no or low 500 watt load.

it will depend on the pressure and the quality of the gas used.
that will depend on the gas supply on the day of run.
 

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Discussion Starter · #3 ·
Thank you, @iowagold.

So, based on your ideas, here's what I plan to do... correct me if I misunderstood something:

1. Start it up on propane at operating RPM (3600) with no load
2. Tighten the screw until the engine starts to lean out
3. Back-off on the screw until the engine starts to run correctly then add half a turn for good measure
4. Put it at 25% to 50% load
5. If it runs lean again, loosen the screw further until the engine smoothens up
6. Remove the load and see if the engine is running lean or rich
 

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yup you got this!
grin!
LP and NG is very forgiving on the mixture as it in vapor gas form before the demand regulator..
I like a bit rich as it starts better.
so if your screw turn range is one whole turn for the rich lean set at 2/3 to 3/4.
and see if it starts when it is cold ok.
 

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Discussion Starter · #5 ·
So far so good.

I got it to 80% load (3,600 W) and the engine sagged a bit down to 58.6 Hz, which is expected when running off of propane. I turned up the throttle screw a very tiny bit until I got it back to around 59.8 Hz. Without load, the engine runs at 61-62 Hz.

I'll just use up the gasoline still in the tank and replace the sparkplug to iridium when it runs out. Thereafter, the generator will run primarily from propane.

It's been fun working on a small engine. I also learned a lot from James Condon's YouTube channel. I can't remember the last time my fingers reeked of petrol.

Before, with the stock carb:


After:
 

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Looks good, I’ve seen those conversions on eBay for years and always wondered if they are worth their mettle.

One of the biggest perks is the location of propane inlet…right at the venturi.
 

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Discussion Starter · #8 ·
As for the stock carb, is it enough to drain all of the gasoline out of it before putting it in storage or do I still need to take it apart and clean it thoroughly with carb or brake cleaner?

This is still practically brand new... used the generator less than 8 hours.
 

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As for the stock carb, is it enough to drain all of the gasoline out of it before putting it in storage or do I still need to take it apart and clean it thoroughly with carb or brake cleaner?

This is still practically brand new... used the generator less than 8 hours.
remove the bowl drain the gasoline out.
blow the carb dry with shop air.
maybe a fog with marine fogging oil before putting back together.
that will keep the corrosion down to a min during storage for long term.
 

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So far so good.

I got it to 80% load (3,600 W) and the engine sagged a bit down to 58.6 Hz, which is expected when running off of propane. I turned up the throttle screw a very tiny bit until I got it back to around 59.8 Hz. Without load, the engine runs at 61-62 Hz.

I'll just use up the gasoline still in the tank and replace the sparkplug to iridium when it runs out. Thereafter, the generator will run primarily from propane.

It's been fun working on a small engine. I also learned a lot from James Condon's YouTube channel. I can't remember the last time my fingers reeked of petrol.

Before, with the stock carb:


After:
Good job and thanks for sharing information. I need to load test my generator on propane. It runs exactly at 60hz with no load on propane but 62hz with no load on gasoline. Your post reminded me that I may have to adjust the throttle spring location, in my case, with propane.
 

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Good deal on the conversion. I did not replace the carb on mine, I made a manifold to inject the gas fuels in to the intake stream.

As to the fuel mixture - I am with Paul. Run it a bit rich.

My small open frame gen I used a small space heater on low, draws about 750 watts, as my test/tuning load. Once I got the fuel mix (natural gas here) set where it ran best I was able to start the generator on natural gas, also. Some say the iridium plugs with small gaps are superior on NG. So keep that in mind. I don't have any yet.

I have 2 gens set up for tri-fuel - small ~2600w open frame rotary and a 15kw rotary. Then I have a Honda EU2200 that is actually my primary generator - it only runs gasoline. It is the primary because it is convenient, quiet, and very fuel efficient. For home back up as long as we have natural gas the 15kw will be used, but we've never been there with it (yet) as it is new this season. So are the gas conversions.

Anywho, options are good! You never know what kind of fuel you'll have available. I am tempted to get a couple more 100lb propane tanks at some point down the road. We'll see.
 

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Discussion Starter · #12 ·
My main motivation to switch to propane is to reduce or entirely eliminate the need to babysit on gasoline. We seldom have power failures but when we do, I need backup power for I am still WFH and my kids are on virtual classes. Along with that, I need to keep a few servers up and the ever important A/C (tropical climate) to cool the house. I can keep a tank of propane on standby and it should last indefinitely. I would still need to test the generator every month to make sure that it works when needed but that’s about the only task, apart from maintenance (oil, spark plug, air filter, etc.), that I have to do. Maintaining the fuel is one less thing I need to worry about.

If the outage lasts longer than the amount of propane I have on hand, that’s the only time I put in fresh gas.
 

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My main motivation to switch to propane is to reduce or entirely eliminate the need to babysit on gasoline. We seldom have power failures but when we do, I need backup power for I am still WFH and my kids are on virtual classes. Along with that, I need to keep a few servers up and the ever important A/C (tropical climate) to cool the house. I can keep a tank of propane on standby and it should last indefinitely. I would still need to test the generator every month to make sure that it works when needed but that’s about the only task, apart from maintenance (oil, spark plug, air filter, etc.), that I have to do. Maintaining the fuel is one less thing I need to worry about.

If the outage lasts longer than the amount of propane I have on hand, that’s the only time I put in fresh gas.
Paul and a couple others on here are a wealth of knowledge. As far as maintenance goes - there are some tricks I've learned from them to prolong the life of some of these small engines.

Proper break-in is very important on all engines. And once broken in using a high quality synthetic oil with ZDDP additive can vastly increase the service life of small engines.

The contrary is also true - if you don't do quality maintenance the service life will be evident of it.

I don't have any direct references to point you to on service life extension, but hopefully some here can chime in and give you some better pointers. For me, I got a good supply of Royal Purple synthetic oil and ZDDP additive. I haven't switched to Royal Purple oil just yet, but have added ZDDP. I bought a bunch of Penzoil Platinum synthetic oil prior to purchasing the Royal Purple so the last oil changes were the Penzoil. My new engine (on the 15kw, Honda GX690) has dyno oil in it for the first 20hrs. I think I'm only at about 7-8hrs on it thus far. Once I hit the 20hr mark Royal Purple is going in.
 

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Discussion Starter · #14 ·
Good idea on the ZDDP. Though, they're pretty much hard to come by where I am, if not expensive.
 

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Good idea on the ZDDP. Though, they're pretty much hard to come by where I am, if not expensive.
Diesel oil.
Lots of zddp, Very shear stabil, comes in all the right viscosity for hot weather and is dirt cheap by the pail

Sent from my SM-G973W using Tapatalk
 

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Motorcycle oils are made to handle heat and high revs. Also have zero viscosity improvers to burn off and have good levels of ZDDP. Look for a synthetic motorcycle oil in your area. I prefer to use Amsoil Synthetic Small Engine Oil, made specifically for these types of applications. See an earlier post…Dutchy
 

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you have to watch some of the larger bike oils as they have the friction modifier for the bike clutches.
not sure on your ams oil does it have that?
 

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Discussion Starter · #18 ·
I am using motorcycle oil now during the break-in period. I did that partly due to the friction modifiers possibly helping with the break-in. But mainly, I did it because basically these portable generator engines have more in common with single-cylinder motorcycles (splash oil system) compared to automotive engines (pressurized oil system). Once the break-in is done, I'll switch to full-synth automotive oil.

Good plan?
 

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True Paul. My fault to not point that out, but Amsoil m/c oils do NOT have friction modifiers, and I keep thinking other oils are similar. Most M/c oils are second best to the purpose built synthetic Amsoil Small engine oils though. Car oils don’t cut it, but will do in a pinch. If you have a cheap knockoff engine you need the best oil. If you have an expensive piece of equipment, you want the best oil too. 😉 Dutchy
Copied the following m/c oil info from the Amsoil website…
Reduces Friction, Heat and Wear
In high heat conditions, AMSOIL Synthetic Metric Motorcycle Oil exceeds the standard for high-temperature film strength to deliver excellent wear protection. It keeps engines running cool by effectively reducing friction and heat, and it contains a heavy treatment of anti-wear additives to reduce wear regardless of operating conditions. AMSOIL Synthetic Metric Motorcycle Oil is thermally (heat) stable and contains maximum levels of oxidation-inhibitor additives. It is extremely resistant to volatility and is engineered to prevent damaging sludge and carbon deposits for superior engine cleanliness.

Smooth, Confident Shifts
AMSOIL Synthetic Metric Motorcycle Oil contains no friction modifiers and promotes smooth shifting and positive clutch engagement. It is engineered to control heat and prevent slippage and glazing, promoting longer clutch life.

Controls Foam
High-rpm operation causes some motor oils to foam. When foam bubbles travel between gear teeth or engine components, they collapse, allowing metal surfaces to contact, causing wear. AMSOIL Synthetic Metric Motorcycle Oil contains advanced anti-foam additives that help prevent foam, allowing riders to confidently push their bikes to the limit.

  • Premium wear protection
  • Smooth, confident shifts
  • Cool, clean performance
 
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