Hybrid Car – More Fun with Less Gas

Natural Gas Conversion: Generac 4000EXL

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Posted by Geoff on June 9, 2005, 4:02 am

Hi all,

Thanks for the tips on setting up my generator, it's going to make
getting ready for hurricane season a lot less stressful.

My second (and hopefully last!) question is about conversion of this
generator to run on NG, with ideally, the option to revert to gasoline
if it becomes necessary.

Looking around I see the main company that sells kits for this is
uscarb, and they have conflicting information about whether it's easy
or not for my model.  One part of their site lists this model as "ANR",
"when the adapter is added, the little plastic button on the tip of the
choke lever must be removed and lever must be cut off or bent up"
"the little rubber crank case vent hose must be extended by adding a

This doesn't sound like the kind of thing I'm going to complete without
blowing up the neighborhood, or at least losing my eyebrows.  Another
part of their site lists it as a standard conversion, without the ANR

Can anyone tell me if this "ANR" marking is correct, or is it simpler
than it sounds?  


Posted by beertender on June 9, 2005, 6:06 am

Hi Geoff,

During my slow months, (winter), I convert 4000EXL's to multi-fuel and sell them
locally and on Ebay.  I tried to find a link to one of my completed auctions,
with all the pictures and descriptions, but they've all past 2 months age and
have been purged.

Here's a link to the "more info" page I included in my auctions:


The USCarb kits are ok.  And they are a good outfit to deal with. (speaking
purely as a past customer)

The spud in kits work great for ng or propane, but you loose gasoline capability
unless you want to swap carbs back and forth.

The venturi kit that mounts between the carb and airfilter do require that
you snip off part of the plastic that covers the carb so you can operate the
choke lever.  But they still work with gasoline.

Also, I've never been able to get close to full output with the venturi kit when
running on ng.  They work perfect on propane.

So I bought a case of stock carbs, and re-machined them for a second jet
into the internal venturi to run on vapor fuels.  Just what you are looking for.

My 4000EXL's run as stock on gasoline, or close the fuel shut-off and open
the vapor fuel supply, and they work just as well on ng or low-pressure propane.

The books all say to expect 10% reduction in power for propane, and 20%
reduction of natural gas because of the reduced btu content in these fuels.

I'm still able to load to full 4kw on propane and engine runs smooth. On ng,
engine starts to sound labored at about 3.2kw, and rpm's drop at 3.5kw.

Right now, I don't have anything for sale. (and if I did, I  wouldn't be trying
to sell it on usenet.)  Mainly because I have No spare time in the summer.

But if you do decide to go with one of the uscarb kits, and don't like it, I
will have stuff,  parts, converted carbs, etc for sale again after Labor Day.  


Posted by Geoff on June 10, 2005, 2:28 am

Zero, thanks heaps for the thorough reply.  I'm definitely interested
in one of the modified carbs; I'm pretty sure I'll be ok with loading
it below 3.2kw, and having the option of going to gasoline is a great

If you definitely don't have a modified carb until after Labor Day, I'm
happy to wait and do the gasoline thing this hurricane season and come
back to you in September.  I'm in FL, and given that I can see snow in
some of the pictures on your info page, I'm guessing that shipping a
modified carb is going to be a lot easier!

If you do turn over a box in the workshop and find a modified carb, let
me know.  You can reach me by taking out the dog:

Or, if you reply-post here I'll contact you from your info page.

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