A warning to those looking to mod their motorized bicycles:

Most, if not all, of the hacks and mods featured on this site were made by individual hobbyists. If you are new to working with 2-stroke bicycle engines, please by aware that there's a possibility that a mod featured on this site could seriously damage your engine. Please don't try any mod from this or any other site unless you fully understand what you are doing. The owner of this blog will not be held responsible for both material and bodily damage caused by performing a modification featured on this blog. Also remember that opening up your engine may void your warranty!

Ethanol Bike

 NOTE: The information on this page was created through personal experimentation.  Use this page at your own risk!  Do not attempt anything described on this page unless you know what you are doing.

How'd you like to make your own fuel for your motorized bicycle?  If that's something that interests the hobbyist in you, then ethanol may be the answer!

What is ethanol?

Ethanol is ethyl alcohol, which is the kind of alcohol you'll find in a beer or any other alcoholic drink.  Yes, you can make your motorized bike run on it.  I've heard from a lot of nay-sayers how evil ethanol is; that it will wreck your engine, melt seals and gaskets, that it just plain sucks as a fuel.  But I'll tell you that it does, in fact, work as a fuel.  Since it's technically a biofuel, it's indeed possible to make your own!  Or you could run your bike on E85 fuel(85% ethanol, 15% gasoline) if you are near a fuel station that sells it!

Why should you use ethanol?

Nothing is without disadvantage, but a lot of people aren't sure of the advantages of running an engine on ethanol.  Among the advantages are:

  • Slightly better for the atmosphere.
  • Clean-smelling exhaust.  This is my favorite aspect of ethanol fuel because it means I'm not soaked with the acrid smell of gasoline after every ride.
  • Cooler burning(when the engine isn't run lean).
  • Can be made at home.
  • Cleans carbon and gunk from the engine and carb.
  • Has the equivalent of a high-octane rating, which means you can take advantage of high compression if you modify your engine.
Here are some of the claims and questions usually posed when ethanol is the topic:

Ethanol will wash away the oil in your engine and cause it to seize or fail.
This is true if you're using normal 2-stroke oil.  2-stroke oil and petroleum-based synthetic 2-stroke oil separates from ethanol, which means the ethanol won't deliver the proper amount of oil but it will wash away the oil in your engine.  The only kind of oil that works with ethanol is an ester-based 2-stroke oil.  I will discuss this later.

It will ruin seals and gaskets.
I have only come across one seal that failed under the presence of ethanol(float bowl seal).  I have not found any other seals or gaskets on my HT engine that are destroyed by ethanol.

It will cause rust in the engine.
Ethanol does absorb water from the air if it sits around for a while.  However, the water that is absorbed by ethanol is distilled or free of minerals, so the water is a poor conductor and less likely to cause rust in small amounts.  Using the right amount of oil also helps prevent contact of water on to a ferrous surface in the engine.  The oil I use, Red Line, contains anti-rust additives.  If you are worried about water in your ethanol, make sure to shake up your fuel before every ride and don't use fuel that's been sitting around for a while.

It will blow up your engine.
Absolutely not!  I've been running my engine on nothing but E85 for hundreds of miles and she still purrs like a kitten!

It gets worse mileage than gasoline.
This is true, since you need to burn approximately 30% more ethanol to properly run your engine on it.  Since our bikes get far better mileage than a car, and since this ethanol is a bit cheaper than gasoline, this doesn't pose much of a problem.  It is possible, through my experience, to run a bike engine with only 15% more ethanol in the mix, but you have to completely disable the idle speed because using so little ethanol causes dieseling(where the engine won't immediately shut off because the heat of the engine is causing the ethanol to ignite without a spark).  You can compensate for the decrease of fuel economy by increasing the compression of the engine by using thinner head and jug gaskets.

Ethanol raises corn prices.
Ethanol is made from the starches from field corn, which is used in cattle feed and not for human consumption.  The starches from field corn are extracted for the production of ethanol, which leaves behind the corn meal with vitamins/minerals/fiber which goes back to feed livestock.  The increase in sweet corn(the stuff humans eat) is a result of other economic factors that are increasing the price of food overall.

It will cause your engine to produce smoky exhaust and eventually burn up.
This is just not true if you use the proper ester-based synthetic 2-stroke oil.  I imagine most of the problems people have with running 2-stroke engines on ethanol, like exhaust and engine failure, are caused by not using the proper oil.  Also, ethanol simply does not have anywhere close to the same particulate output that gasoline does.  The mix of ethanol I use in my engine produces smoke-free exhaust and it smells very clean.  With the 15% of gasoline in E85, the exhaust smells mildly sweet(believe it or not)!

Ethanol takes more energy to make it than what you get out of it.
This may have been true 30 years ago.  With better technology in ethanol production, it produces 67% more energy than it took to produce it(according to the government).  If you want to make your own ethanol, you can even go as far as to use a solar-powered distilling process and green waste!

So I bet by now you're wondering if ethanol is better for the environment.  I'm not really into using ethanol for environmental reasons, but here's the data if you want to know:

According to the U.S. Energy Department, on average, all regulated emissions either decreased or showed no statistically significant difference between E85 and gasoline. Emissions that increased with the use of E85 included formaldehyde, acetaldehyde, and methane.

The tests by the Energy Department showed that compared to gasoline, E85 fuel produces up to 20% less Carbon Dioxide, 8% fewer hydrocarbons, 70% less benzene, 18% less Nitrous Oxide, and 34% less particulate matter.

Keep in mind that these tests were done with Flex Fuel vehicles and not 2-stroke engines, and the fuel used was E85 and not pure ethanol; but clearly there is a significant enough decrease in greenhouse gases and particulate.  It's still not a clean fuel, but much cleaner than gasoline.

Converting Your HT Engine to Run on Ethanol

Here is what you need to do to convert a 2-stroke bike engine to run on ethanol.
  1. Ethanol resistant seals and gaskets: In my experience, almost all of the gaskets in a 2-stroke HT engine can resist ethanol corrosion.  The only one that didn't was the float bowl seal on the NT carb, which melted immediately.  All you have to do is buy some gasket material from an automotive store and make a replacement gasket for it.  To be sure, you can replace all the gaskets and seals on/in your engine, but I have not yet found the necessary.
  2. Fuel line: If you haven't already replaced the stock fuel line fron your kit, replace it with some quality fuel line from an automotive store.  Ethanol may cause the stock fuel line to harden and fail.
  3. Rubber gaskets: The rubber gasket on my petcock hardened and shrank, and so did the one on the release screw on the carb.  They were made of the same red material.  Just replace them with equivalent rubber gaskets from the hardware store.
  4. Ester-based oil: As I explained earlier in this page, any petroleum-based oil, including synthetic, will separate from ethanol and this will cause engine failure.  You will need a synthetic oil that is ester-based.  The oil I use is Red Line 2-Stoke Racing Oil.  I buy it for $9 a bottle at a local motorcycle supply shop.  There are plenty of other brands of ester-based 2-stroke oil, but make sure it's completely ester or poly ester based before you use it.
  5. Spark Plug: Research has told me that you need a cooler spark plug for use with ethanol, but I have not found this to be true with my HT engine.  I use an NGK B6HS spark plug with ethanol and it performs just fine and cold starts.  If that plug doesn't work for you, try an iridium NGK plug.
  6. Petcock: For reasons of poor flow, you should have already thrown out your stock petcock!  But with ethanol, the rubber "washer" in the stock petcock will shrink a bit and your petcock will become leaky.  The design of the stock petcock is cheesy anyhow, so just replace it with a better quality one or a brass ball valve that fits in your fuel tank.  I replaced my petcock with a brass barbed spout and connected a plastic petcock I bought from OSH to it.
  7. Float needle: I have heard that some of the NT carburetors have a float needle with a plastic tip.  Ethanol may cause this plastic tip to swell up and ruin fuel regulation.  However, the float needle in my carb does not have a plastic tip and is just bare metal.  Check your float needle, and if it's just metal, then you're good to go.
  8. Main jet: Because you need more fuel in the mix for your engine to properly run on ethanol, you need a jet that's approximately 30% larger.  The jet on a stock NT carb is usually the size of a #70 drill bit.  You can actually run your bike on ethanol with the original jet size, but you will have to keep the choke up about halfway the whole time and your engine will run hot.  To make your jet the right size, you need to drill it larger with the correct size mini drill bit.  A #67 drill bit(15% larger) is the very minimum you need to run your engine on ethanol without the choke, but with such a lean condition your engine will run hot enough that the fuel will burn even without a spark causing your engine to rev out of control(dieseling).  Using this size jet will get you more power and better mileage, but your engine will get really hot and you'll get dieseling.  If you face such a situation, disengage your clutch, turn off your petcock, pull up the choke, and hold down the kill switch.  The engine will eventually stop dieseling.  If you are in the middle of traffic and don't have room to do this, instead let the engine stall out by instead coming to a complete stop with your brakes without pulling on the clutch.  If you really want to run your engine this lean on ethanol, you'll have to completely turn off your idle speed to avoid dieseling.  For your engine to run properly on ethanol, you should drill out your main jet with a #64 drill bit, which is 30% larger and just what we want.  You will see a bit of a loss in power, but you will no longer have dieseling and you should be able have your engine idle properly.  You can increase your jet size to #60, which is 40% larger if you find it necessary.
  9. Higher compression:  This is purely optional because while you don't need to do this to get your bike to run on ethanol, you can do things to raise compression to take advantage of ethanol's high octane rating and get back some of the power you lost.  The two best way to do this is to replace the head gasket with a thinner one.  Thinner head gaskets are available at sickbikeparts.com.  You would probably have to make your own jug gasket to get a thinner one, but this isn't recommended because a thinner jug gasket may affect timing and the clearance of the piston on the ports.  Just make sure when doing these thigns that the decreased area between the piston and the head does not cause the piston to hit the spark plug.  Some people run their engines without a head gasket at all, and while this will get you even more compression, this is not recommended.  There are also high-compression after market heads you can buy.
Given that all these steps are completed, and some slide needle tweaking, you should be able to turn your gas-powered bike into one powered on booze!

Difference in Performance and Operation

There are some slight differences in performance when changing to ethanol.  There might be a slight delay in throttle response, though I really only noticed this when I was running the engine with the original main jet.  With other small engines, people have reported having a hard time cold-starting.  I live in a Mediterranean-type climate at sea level, and this hasn't been an issue for me.  You might also have some trouble starting in the cold of the winter.  You can solve this by either warming up your carb float bowl a little bit, or you can spray some fuel right into your intake and try again.

As far as drive performance, you will probably see a bit of a decrease in speed and power.  Though the bike still keeps up a good pace.  I have also noticed that while overall speed may be down, uphill power maintains very well.

Where to Get Ethanol Fuel

You have two options for ethanol fuel: making your own or finding a station that sells it.  To make your own ethanol fuel, you will need to either buy or build your own still.  To do this legally in the U.S., you will need to obtain an alcohol distillation permit. 

There are fuel stations around the U.S. that sell ethanol in the form of E85 fuel.  However there aren't that many E85 stations around.  There are websites on the internet that will show you where these stations are located.  I live in L.A., and the station I get my fuel at is Conserv Fuel on San Vincente Blvd.

Further Questions
When replacing a plastic component, what kind of ethanol-resistant plastic should it be replaced with?
What you want is a kind of plastic that will hold up well with both ethanol and gasoline.  The plastics that work best with both ethanol and gasoline are High-density polyethylene(HDPE), teflon, and tefzel.  There are plenty of other plastics that work with ethanol but will deteriorate from exposure to gasoline.  

What about the float in the carb?  
The plastic float in my stock NT carburetor has not deteriorated(yet) from ethanol.  I don't know what plastic it's made of, but my guess is that it's made to handle a certain percentage of ethanol in conventional gasoline, so it should be just fine.

I like being able to make my own fuel, but what's the point if I can't make my own oil?
The base stock for ester based 2-stroke oil is very similar to biodiesel!  The problem is that 2-stroke oil contains various additives that make it work better with air cooled 2-stroke engines, and I don't know exactly what those additives are(or if they're really necessary)!  From what I know, those chemicals include a dispersant/detergent, anti-wear agents, biodegradability components, and antioxidants.  So I can't tell you how to make your own ester based 2-stroke oil, but there's hope that someday it may be possible to make both your own fuel and oil!  However, it may be possible to use straight de-gummed castor oil, but at this time I'm not certain if it will work with ethanol and using castor oil means having to regularly open the engine head for cleaning or inspection.  Someday I may experiment with homemade ester oil and castor oil.

Can I still run my engine on gasoline if I wanted to?
Yes!  But you'll have to open up your carb and change the jet back to the stock size(#70 drill bit) for it to work on gasoline again.  So if you wanted to switch back and forth, you would need 2 jets to switch out each time.  It might be possible to just use high-octane fuel(aka premium) and not have to switch the jet, but I have not tried this yet.

What jet size and clip setting do you use?
Right now(when I wrote this), I drilled out my jet with a #60 drill bit, which is 40% larger than the stock jet.  This is actually a little too rich, so I leaned it out by putting the slide needle clip to the leanest setting and the bike operates properly.  The reason I used a #60 is because it was one of the smallest bits I could find at a local store.  I got a #67 bit from a small Dremel drill bit set from Home Depot, but it was too lean and I was getting a lot of dieseling.  Ideally, you would want to drill your jet out with a #64 drill bit, because you could probably leave your slide needle clip at the same setting you use with gasoline.

How do I drill out my jet and what if I make the hole too large?
Drilling out your main jet is very easy and all you need is the drill bit; you don't even need a drill.  Just hold the jet in one hand and the drill bit in your other hand, and turn the bit through the jet hole until it makes its way all the way through.  It only takes a few minutes.  If you made your hole too large or if you want to try a smaller jet size, you can heat up the jet with a torch or a soldering gun/iron and fill the jet hole with just a tiny bit of rosin core electronics solder.  Let it cool, and then you can re-drill it to your desired size.

What is the octane rating of ethanol?
The equivalent of an octane rating for straight ethanol is 96.  Some sites say the octane rating of ethanol is up to 112, but this is a miscalculation.  For those reading who don't know, the octane rating of a fuel is a measurement of how much compression the fuel can withstand before detonating.  Since ethanol has a higher octane rating than gasoline, you can take advantage of it by raising the compression of your engine which would give you more power.

What oil-to-fuel mix do you use?
At the time I made the video and wrote this page, I was using a 32:1 mix of E85 to Red Line Ester Synthetic 2-stroke oil, which is the standard mix ratio for gasoline.  I have recently switched to a 40:1 mix, and this seems to work just fine.

Can I use denatured alcohol from the hardware store?
Absolutely!  It won't be nearly as cost-effective as using E85 or making your own ethanol, but as long as the alcohol you are buying is only ethanol and/or methanol(no additives), it will work just fine.  I have not experienced any noticeable performance differences when running my bike on denatured alcohol.