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specialgreen · Posted: Mon Jul 12, 2004 1:29 pm Post subject: E-85 small-engine conversion

Cars are the only Flex-Fuel Vehicles you can currently buy. However, any four-stroke gasoline engine can be converted to burn E85. Small engines are good candidates for an E-85 conversion, because they are carbureted (modifiable using common tools), because their emissions are often not regulated, and because the short length of the intake manifold helps heat the ethanol for a good burn.

Ethanol contains oxygenates, which means that more oxygen is present when E-85 is being burned in the engine. To have the correct mixture of fuel and air, you need to add less air (or more fuel) into the engine. The carburetor is responsible for mixing air with fuel. The big change which needs to be made to burn E-85, is to make the carburetor spray fuel at a higher rate.

A typical carbureted engine has an exhaust port (possibly connected to a muffler or silencer) and an intake port. The intake port is connected to the carburetor, which mixes fuel and air. The carburetor has a fuel line to the gas tank, and is connected to the air-filter box using a horn-shaped air intake:

On my motorcycle, the carburetor sits behind the engine, and forward of the air-filter box. Once you've located the carburetor, look for an "idle adjust screw" or "enrichment screw". This screw is used to pinch-off either the air or fuel as they enter, changing the air/fuel mixture ratio. You may want to make a note of how the screw is set with gasoline: count the turns, while turning the screw all the way in. Now play with the mixture a bit by turning the screw while the engine is running. At both extremes, the engine will run rough; with the screw set properly, the engine RPM will run fast and smooth. You will find that as you turn the screw in one direction, the engine RPM will pick-up quickly, then slowly the RPM will get lower again. As you turn the screw in the other direction, the opposite will happen: RPM will get slowly faster, then quickly the RPM will drop. From the point at which the mixture is "just right", the direction which drops-off quickly is "too lean", or not enough fuel. The direction which drops off slowly is "too rich" (and you may smell fuel in the exhaust). This difference will be even more pronounced with E-85 than with gasoline, since E-85 will run "rich" without too much roughness.

For our purposes (tuning the carburetor to burn E-85), begin by setting the screw all the way towards the direction of having too much fuel ("richer"). At this point, with the mixture screw set all the way to "rich", if you switch from burning gasoline to E-85, the engine might run. But probably, it is still way too lean, and needs more fuel. We will probably need to "rejet" the carburetor to cause it to send even more fuel.

To get at the carburetors on the motorcycle, I need to remove the air filter box. Then the twin carburetors are visible, with their horn-shaped air intakes:

Most small engines will have one cylinder and one carburetor, but most motorcycles have one carburetor per cylinder.

Here, I pull the motorcycle carburetors (silver colored) away from the engine intake ports (black):

Next, we need to open the carburetor. Turn the carburetor over; the bottom of the carburetor will probably be smooth with rounded corners, and is called the "bowl". The bottom of the carburetor serves a function similar to the water reservoir on a toilet, except that the carburetor bowl holds fuel. In this picture, the carburetors are sitting upside-down, and I am removing the screws which hold this "bowl" onto the bottom of the carburetor. You can see the black fuel hoses which bring fuel from the gas tank:

Inside the carburetor bowl, there will be a plastic thing called a "float", attached to a very small pencil-shaped plug called a "float needle" (on my carburetor, the float needle is about 1cm long). The float's job is to float on top of the fuel (remember, the carburetor is upside-down now). When the fuel level is high enough, the float pushes the pencil-shaped plug up into the fuel line, stoppering the flow of fuel from the tank. Be careful with these parts; there is a gasket between the bowl and carburetor, and an O-ring where the float slides into the carburetor; and there may be a fragile metal tab connecting the float with the float needle.

Remove the float, and put it and the float needle into a baggie for safekeeping:

Below the float, you'll see one or more brass plugs. They may be flush with the bottom of the carburetor, or they may be sitting inside little metal "towers". The brass plugs are called "jets", and work similarly to an old brass garden hose nozzle. The size of the hole in the end of the jet limits how fast the fuel can be sprayed into the engine. There will usually only be one jet for engines which have one fixed speed and no throttle (like most lawnmowers, snowblowers, etc). Engines which have a throttle (like weedwhackers, chainsaws, etc.) will usually have two jets. The carburetor in this picture has two jets: the large one in the middle, protruding from a little "tower"; and another, smaller jet which is sitting deep down in the other little "tower" (which I am removing with a screwdriver,
in the picture):

We need to enlarge the hole in the jets. They are removed just like screws or bolts, using a screwdriver or wrench as appropriate. After removing the jets, you should be able to see a small number stamped onto each jet. For example, a jet marked "40" would have a hole 0.4 mm in diameter (which is very, very small!). Some American carburetors may be identified in inches ("40" meaning 0.04 inches). You can enlarge these holes using small craft drill bits from a hobby store ($1.50 each at the hobby store in my neighborhood). You can hold the drill bit using an Exacto knife handle, press gently and turn slowly and smoothly using your wrist. Little brass shavings may fly out; and the drill bit is about the size of a mechanical pencil lead, and can snap, so please wear eye protection:

Increase the jet sizes in small increments, and test the engine each time, so that you can tell when you've enlarged the jets too much. You will probably end-up enlarging the hole in the jet by between 25% and 40% over the original size, for good operation with E-85 fuel (so a 0.4mm hole would probably be enlarged to between 0.5mm and 0.56mm, such as with a #75 or #74 drill bit). As you enlarge the jet, the engine will probably run more smoothly... but then you will probably enlarge the jet too much, and the RPMs will begin to go down again, as the mixture becomes too rich. At that point, you can adjust the mixture leaner again using the Idle Adjust screw (which you set to its richest setting earlier). Just like before, turn the screw from one extreme to the other, until you get a feeling for where the RPMs are highest.

If you find that you have enlarged the jet to be too large, and cannot adjust it lean enough using the adjustment screw, then you will have to replace the jet. Replacement jets are available in a variety of sizes from many small-engine repair shops, including marine, motorcycle and ATV shops. Take your old carburetor jet to such a shop, and they can probably help find a replacement. New jets cost about $2.50 each.

It will take some experimentation to find jet sizes which make your engine run smoothly using E-85 fuel. When you have tuned the engine to burn E-85 fuel, it will not run on plain gasoline anymore. If you should wish to retune it for gasoline, then you'll need to replace your enlarged jets with the factory sizes.

specialgreen · Posted: Tue Jun 14, 2005 2:01 pm Post subject: Re: E-85 small-engine conversion

One poster here ( http://e85forum.com/viewtopic.php?p=98#98 ) mentioned running E-85 in his unmodified lawnmower. I'm a little surprised; maybe his lawnmower had a rich enough mixture? Or perhaps a lawnmower is a little more forgiving than a motor vehicle, and can handle the E-85 with less fanfare.

In any case, it sounds as though carburetor modification is not always required to burn E-85 in a small engine.

juniorace · Joined: 27 Jun 2005 Posts: 2

I am curious about running E85 in my 2002 Suzuki GSXR600 motorcycle. I have a Dynojet Power Commander installed on the bike which allows for the air/fuel mixture (fuel injection, no carbs) to be "remapped". I have thought about having the bike put on a certified Dynojet dyno, and then having the bike remapped with the E85. I can also adjust ignition timing during the dyno session. Would there be anything else to consider with the engine besides what I have already mentioned? I can literally download one map from a laptop to the Power Commander to alter the fuel/air mixture to run E85, and then download another map to switch back to regular fuel.

Guest · Posted: Mon Jun 27, 2005 9:59 pm Post subject:

You might run into flow issues, if the injectors aren't up to the task. They need to flow maybe 30% more fuel. But the dyno operator should be able to tell you whether E-85 is too lean even at max enrichment, WOT.

Other than that, if you want more power, then you might want to get some domed pistons (and optionally shave the head & degree the cams) before you go through the expense of the dyno. But if you just want to burn ethanol, then no increase in compression is needed.

I should also mention that motorcycles have small gas tanks (compared to cars). Losing some MPG on a motorcycle can be really annoying. Also, it isn't completely practical if you want to ride outside Minnesota/Iowa/Nebraska, etc. I carry a gascan of E-85 when I go hit the twisties in Wisconsin.

juniorace · Joined: 27 Jun 2005 Posts: 2

I would be doing the dyno session no matter what, just to get the benefit out of the exhaust system I have installed. As you can understand, one cannot get the true benefits out of performance system improvements without "tuning". I have an E85 station within 2 miles of my house and another within 20 mile. E85 is just something that I am quite interested in....and trying it in my bike has been "gnawing" at me.

specialgreen · Posted: Tue Jun 28, 2005 8:10 pm Post subject:

In that case, yep, it should be OK, if the injectors are up to it. Actually, it should run very well, compared to my setup.

Also, E85 will wash-out rust and gunk from the tank, so be sure to add a fuel filter below the tank. Actually, you might want to clean and kreem your tank beforehand; ethanol can eat through lead/tin coated steel over time. Some tanks are stainless or nickel-coated; my '92 Suzi is OK after 2 years of E-85 on the stock gas tank... but you never know.

86spree · Joined: 19 Apr 2006 Posts: 5

I've seen several comments on 2-cycle engines and E85. Suggestions and comments welcome on putting E85 in my Honda Spree without aterations and/or with....

Thanks for the comments and suggestions in advance!

specialgreen · Posted: Wed Apr 19, 2006 3:00 pm Post subject:

Regular mineral-based motor oil doesn't mix with ethanol; I don't know whether 2-stroke oil is mineral or vegetable, but mineral 2-stroke oil may not mix at all. Veg (e.g. castor oil) or synthetic would probably mix and not separate, but test in a bottle to be sure.

86spree · Joined: 19 Apr 2006 Posts: 5

let me clarify...the spree doesn't require mixed gas...

Any further comments and suggestions would be great.

specialgreen · Posted: Sat Apr 22, 2006 8:05 am Post subject:

I don't know much about two-strokes. If the "oil injection" they use is a fine mist, like a fogging oil, then perhaps the lubrication need not be miscible with the fuel. But if the injection is simply injecting a metered amount of oil into the intake manifold, then the fuel/oil would still "mix". They just wouldn't "pre-mix".

When I was looking for a bio-oil for my motorcycle, I ran across some notes about use of ethanol in two strokes at the Illinois Institute of Technology:

compudude86 · Joined: 20 Feb 2006 Posts: 47 Location: algonquin, IL

sorry, i shouldve clarified more, i meant gas/e85 mix, and the oil mixes in the engine
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running a 95 buick century on e-85, yes it can be done!!

specialgreen · Posted: Sat Apr 22, 2006 3:29 pm Post subject:

Yep, "Engines that use oil injection systems are not as prone to this gas an oil separation since the oil is added at the last possible instant". It sounds like you may be able to get-by using E-85 with regular 2-stroke oil. I'd be tempted to try it, just to post the results of how well it works! But if you were cautious (like if you're fueling a classic PX200 Vespa, and don't want to damage it), then I'd try biodegradeable 2-stroke oil or synthetic 2-stroke oil instead.

If you have a engine that you don't mind experimenting with, then you could try E-85 and post your (hopefully) success story here!

86spree · Joined: 19 Apr 2006 Posts: 5

Thanks for all the great suggestions. I am fortunate to have an E85 station here in Janesville (Suburban and Tahoe capital of the world...well they build them here). I will be contacting the Illinois resources listed and trying within a few weeks. I'll keep you up-to-date.

Now, if I wouldn't have traded in my 2001 Taurus FFV Wagon for a Venture...

Steve

86spree · Joined: 19 Apr 2006 Posts: 5

I purchased the Pennzoil Synthetic tonight and will fill up tomorrow afternoon. I'll keep you posted. Again, thanks for all the help.

BURNALCOHOL · Joined: 19 Oct 2005 Posts: 50 Location: Raymond,NE

Great topic specialgreen. I like all the pictures you added in. Well done!
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Jeremy Nicholls