Instructions & parts: tri-fuel gasoline natural gas propane conversion generator


Mar 2, 2009
Camarillo, CA
I also posted this as a follow-up to my original thread here:

finished and tested the conversion of my two cheap Harbor Freight generators to tri-fuel, a list of all parts and sources at the bottom.

[I procrastinated forever, as I was afraid to touch the generator/carbourator... I am a software guy and tend to break hardware :) but we had a planned power outage, so while running one generator on gasoline, I converted the other to tri-fuel, then swapped them and did the second one.]

overall I like these generators, they always started on the first pull, run fairly smoothly, and for a non-inverter generator, the power is "clean" enough:

it will power up my UPS, and the UPS does not go into battery mode, i.e. the UPS "believes" that the power is "good enough"

the voltage display seems fairly steady but the cycles vary at about 60.5 +/-1Hz

though I do want to look into some sort of power conditioning as someone recommended in the original post: battery charger, battery, inverter.

a single generator had no problems running two refrigerators, freezer, internet modem/router, computer, two large air filters, even on natural gas, which has a lower energy density

the CARB version of the generator has a charcoal canister which is in the way of the taller tri-fuel carb, so I had to remove the canister and clamp the hoses leading to/from the canister. I also needed to cut off the metal tab which was welded to the generator's frame.

other than that, the conversion was very straightforward, even for a software guy with two left hands:
drain gasoline and shut off the gasoline supply valve
remove air cleaner cover
remove two nuts attaching the air cleaner to the carburetor
disconnect fuel hose and throttle control from OEM carburetor
slip carb off the bolts keep it straight up, as it is still filled with gasoline.. found out the hard way :)
reverse with the tri-fuel carb (I did take pictures so I'll know how to put it back together)
since I've already installed the wheel kit, I had to remove one wheel to allow the taller tri-fuel carburetor to slip onto the bolts.
and I also had to adjust the engine speed screw after installing the new carb

as I mentioned in the original post, there are two versions of the Harbor Freight generator from two different suppliers and I happen to have one of each, these two videos are the closest I found to the two I have:

if you get a new generator, you have to run it on gasoline for about two hours to break-in all the rings/seals/etc before you run it on natural gas or propane

List of parts

coupon for the generator:

tri-fuel carb (note this is specific to the above engine size)
TONCO 170F SAFER for generator GX200 Dual Fuel Carburetor LPG/NG conversion kit

the tri-fuel carb has a barbed nipple that needs to be adapted to a 3/8" gas flare female.
the only way I could think of making this adapter was to get a hose that has the 3/8" flare female on both ends
cut about 3-4" and slip onto the carb barbed nipple, secure with a clamp.
Flame King Thermo Rubber RV Slide Out Hose Assembly, 60 Inch, 3/8 Inch ID, Female to Female -100159-60

hoses and fittings:

expensive and probably an overkill, but was told that I need to ensure that enough natural gas reaches the generator...

3/8" to 3/4" fitting (between the 3/4" supply line and the 3/8" flare female attached to the carb)

even though I got the quick disconnect hose above, I also got this ball valve, and a "T" fitting so I could tee off the gas supply to the water heater.
Homewerks VGV-2LH-B4CB Gas Ball Valve x Female Thread, Brass, 3/4-Inch, 0.75-Inch

hose and regulator for the propane tank:
Gas One 4 ft High-Pressure Propane 0-20 PSI Adjustable Regulator with QCC-1 type Hose - Works With Newer U.S. Propane Tanks

fitting between the 3/8" flare female on the carb, and the propane tank hose above, since both are flare female

Conntek GEN1688 L14-30P to Multi-Outlet Power Cord 30 Amp 4-Prong

very important, need an hour meter to know when to change oil, and tach to make sure it is running at 3600rpm (aka 60Hz)

optional stuff:

to make oil changes much easier:
Drainzit HON1010 Oil Change Aid For Honda 2.5HP 4.5HP 5.5HP 6.5HP 10mm

WEN 55201 Magnetic Oil Dipstick for Inverter Generators (compatible with WEN, Yamaha, Predator)

also, I got the better NGK (6427) BPR6EY Spark Plug (replaced after engine break-in on gasoline)
So are you running this on natural gas, propane, or both?

I have a similar kit. Started with a 0.5 lb regulator and hose cut off a standard barbecue, stuffed on the barb and clamped. Didn't like it, and discovered the barb unthreaded from the carb, allowing a standard pipe thread regulator-hose to be installed.

Mine barely starts on propane. There's that spring-loaded primer button but it basically just allows a cringe-worthy backfire most of the time. My generator has
So I start it on gasoline, shut that petcock off, count to five for the carb to drain, then turn on the propane-- slowly, to avoid tripping the leak detector in the regulator.

The great news is all the air (and propane) rushing through the gasoline part of the carb thoroughly dries it out for easy starting the next time around.
Keep in mind that running on propane will typically burn the valves after awhile. That is something that seldom happens with gasoline engines. Unsure if engines designed for propane have valves made of a different material than ones made for gasoline.
Originally Posted by Rand
I thought the propane burning valves was debunked?

I have the old engine from a WinCo propane generator. The engine was replaced due to burned valves.