Since the early 70s I have made a living in the powersports industry and still do. Trained at what was at the time the nation's most respected two-year mechanics school 1; followed by Honda and Kawasaki factory certification (1983 and 2005, respectively, with Honda re-certification in 2003) as well as scores of Yamaha, Suzuki, and Harley-Davidson courses; a metro (L.A. and Phoenix) area (authorized dealer and independent) mechanic for well over fifteen straight years; for five years a trainer for the well-known Motorcycle Mechanics Institute 2; for several years MMI's system-wide curriculum developer with oversight over both campuses and more than 4,000 hours of content; eventually eight years an instructional designer at Kawasaki's U.S. headquarters as well as a roving trainer that traveled across the country delivering instruction at venues of many types. Very recently I was for three more years manager of Kawasaki dealer training tasked with the operation of six full-time training centers, 50 satellite locations, eight travelling trainers, equipment, vehicles, supplies, technician certification, training logistics, and the creation of training content both live and online for Kawasaki's entire U.S. 2,000-dealer community. 3, 4 Today I have a shop specializing in the restoration of a limited selection of vintage Honda carburetors and engines. Folks send me carburetors from as far as Norway and 70s Honda motorcycles from all over the U.S. for me to repair. Bottom line: I'm not your typical Internet "expert".
It's astonishing how clueless the loudest voices in the industry are when they talk about carburetion. Did you know that adding cylinder compression richens carburetion (and that low compression leans it)? You've probably never heard that before, I would bet, and most user forums communicate just the opposite. Did you know that the real benefit of high performance ignition coils is that they likewise richen carburetion? Yup. That's their claim to fame, not magic sparks. Did you know that high performance jet kits in most cases actually compensate for shortcomings in vehicle maintenance (meaning if this neglected maintenance was performed the kits would be superfluous), and do not on their own deliver increased performance? No? I'm not surprised. Did you know the powersports aftermarket has been lying to you all these many years about bikes being manufactured "too lean". 5 They aren't; never have been. Pure bunk. Are you aware that despite Internet "wisdom", modifications to a streetbike's air intake impact carburetor mixture more than ten times as much as do any changes to the exhaust? Yes, ten; and yes, intake, not exhaust. And this in turn is tied to federal sound regulations, not emissions, and not "stupid factory engineers". And that for 70s and 80s Honda streetbikes no aftermarket exhaust can possibly increase performance by any means other than increased noise and decreased weight? This fact is related to camshaft design. Why then is there so much slavish, uninformed focus on exhaust and virtually none on intake, in the powersports media? Hmm? Think for a moment about this. And finally, did you know it's not what's *in* today's gasoline that makes it a problem but rather what's *not in it* that matters; that what is missing from it is the real concern? No? I didn't think so. Why aren't these things better known, and why are bike forums instead enamored with Chinese replacement parts; "velocity stacks"; repair practices originating in, at best, 1940s car manuals, and at worst the imaginations of unqualified hacks; the weight of mass opinion; "M boxes" and a myriad of other vacuous and meaningless things? Why indeed! I don't really know, but the fact that they are should indicate something. If the important things are being overlooked and downplayed by the industry's pundits, and they definitely are, should you be putting your trust in what they disseminate about ethanol? 6
Let's begin at the beginning. Why is gasoline oxygenated, that is, additives such as ethanol added to it bearing oxygen chemically? One word: Emissions. Fuel oxygenates first and foremost constitute a sort of passive emissions control program. They do something a little "Big-Brotherish": they unilaterally force early model vehicles to comply with much later model emissions standards, standards they were never designed to meet. These (innocent, unsuspecting) vehicles are the sole target. Later, more modern vehicles aren't affected. 7 But the older, target vehicles lean out slightly in the presence of ethanol gas, improving exhaust emissions. But doesn't this affect performance? No. Because manufacturers build into every vehicle something quite interesting: a margin of over-richness for driveability and reliability. The driveability concerns different sales destinations, the reliability a hedge in terms of warranty. This of course includes motorcycles. Every streetable motor vehicle has this margin. Ethanol, MTBE, and other oxygenates take advantage of, manipulate, capitalize on, this rich margin for emissions purposes, by targetting it and very carefully and very slightly reducing it for the emissions-control goal. The manufacturers put that margin in there, the government preempts and tweaks it to their advantage. The result is as intended: reduced exhaust emissions with no bad effects. That's the *why* and the *how* of ethanol. 8
Note that I said, "no bad effects." Ethanol is not the evil scourge media says it is. That's a fairy tale. The American Motorcyclist Association (AMA), in its usual style and arguably what it's best at, is perpetuating a myth. Just as with the scare-mongering the AMA engaged in during the 1980s concerning tetra-ethel-lead, today they are similarly popularizing the notion that oxygenated gasoline is harmful to powersports vehicles. And the rest of media has run with the ball. And how! But let's put on the brakes. Let's look at this fallacy in terms of its three most insidious claims: corrosion, loss of performance, and chemical damage of rubber components. Plus, we'll visit a fourth, related misconception regarding ethanol and modern gasoline's very short shelf life. Here we go.
First, corrosion. The idea that oxygenated gasoline corrodes carburetors started in the marine world, and it is in fact the National Marine Manufacturers Association (NMMA) that began all the current hoopla by lobbying the government concerning ethanol gas. Subsequent to the NMMA's involvement, the AMA joined the controversy. 9 The simple fact is, marine carburetors, where and when they still exist, have (had) bimetallic construction, that is, steel float bowls bolted to low grade aluminum carb bodies -- a dissimilar metals combination that is a sure recipe for electrolysis-generated corrosion, especially when combined with a life near water. You find this same bimetal construction on your lawn mower and portable generator, by the way. But not on any motorcycle made in the last 80 years. Certainly, the presence of moisture is going to wreak havoc on this kind of carburetor, and I don't fault the marine industry for its concern. Of course, with fuel injection this has become moot, but I think the marine industry would better have served its customers by long ago bringing its fuel systems into the modern era. And since stationary engines use the very same carburetors, maybe those manufacturers should be advocating alongside the NMMA. But guess what, they aren't.
An unfortunate corrollary to this is that the motorcycle industry for a long time made their own version of very corrosion-prone carburetors. Up til around 1978 in fact. While not steel combined with aluminum like marine carbs, bike carbs were however at one time cast of a very low grade aluminum alloy heavy in zinc because this metal was easiest to manufacture. 10 This high-zinc alloy made these carburetors very susceptible to corrosion. In worst cases they simply wear away before your eyes, slower or faster depending on the environment they live in. But it is incorrect to blame oxygenated fuel when these zinc carburetors corrode. They have always corroded more than other carburetors -- much more, and ethanol gas is not appreciably hastening that. No motorcycle, ATV, scooter, personal watercraft, snowmobile, or recreational vehicle's carburetor is more than slightly more at risk for corrosion due to ethanol than before there was ethanol, and post-1978 carbs never were vulnerable (by 1980 few manufacturers were still making zinc carbs -- Euro makers being the holdout).
Second, performance issues. Remember that richness margin oxygenated fuel targets and preempts? Normally, there is no harm in this. The factory-supplied margin, even reduced slightly (but not entirely) by ethanol, is enough to do the job it was intended to, when the engine is healthy. 11 But that "if" is important, because you can't escape the fact that narrowing the margin does *potentially* put the engine a little bit at risk; placing the engine onto a steep precipice from which it can, under the right conditions, fall. And fall it does when maintenance is neglected; when there are tuning shortcomings. When that happens, when the engine is poorly cared for, the bike's fuel needs are then pushed deeper into the margin, a margin now reduced due to oxygenates, and performance can suffer. But this is all worse-case scenario. It's not even close to being a given, and more importantly, it is not the gasoline's fault. It's the bike's. Most motorcycles are badly maintained, and vintage bikes most of all. It's just a fact. Consider this: all of us on the inside of the industry (mechanics and other motorcycle "lifers") are using readily-available oxygenated pump gas without a second thought and without consequence. Ethanol gas is a concern in terms of performance only when the bike has low compression, dirty carburetors, neglected ignition components, and other maintenance shortcomings.
Third, the supposed deterioration of rubber parts. This one is simply a misunderstanding common among folks who have little or no history in the motorcycle field. There is a lot of crap out there masquerading as carburetor parts, kits and similar parts that no concientious mechanic would ever use. These parts do indeed fail to hold up. However, no high quality stock or aftermarket replacement rubber parts swell or break down any more than they did back in the 60s and 70s long before ethanol fuel was common. What, they do swell? Yes, even the OEM stuff. Ask any longtime career mechanic about the slight swelling of factory float bowl gaskets, not in use but when handled after being doused with gasoline. 12 This is not a Viton versus buna rubber issue. Not at all. It's more a $3 carb gasket versus a 50-cent gasket issue. And it's always been that way.
Finally, there is the myth that oxygenates in the fuel cause it to break down and go bad faster. This is silly. It's inarguable that modern gas breaks down surprisingly quickly, much faster than it used to. 13 However, as with so many things, the Internet "experts" have got this one backward too. It's not the oxygenates that make the fuel break down faster but rather the removal of the aromatics (benzene, toluene and xylene) that were common in gasoline fifty years ago that result in our fuel's short storage life. The aromatics are no longer there to preserve it. That's right. It's not what's *in* the gas but what's *not* in it that is the problem, when it comes to fuel deterioration. 14
Let's recap. First, carburetor corrosion has more to do with the quality of the carb's manufacture than with ethanol, though admittedly ethanol's moisture-attraction potential doesn't do these zinc carbs any favors. Second, performance issues do potentially exist due to ethanol but the plain truth is, they materialize only when combined with poor maintenance, and inadequate maintenance is endemic in the powersports world. Third, only the very poorest aftermarket rubber parts deteriorate in the presence of ethanol and occasional slight swelling of good quality gaskets during service operations is normal and to be expected whatever the fuel. And fourth, the powersports industry has recognized (and communicated) for many years now that modern gasoline gels (starts turning to varnish) in as quickly as three weeks, due to the removal of gasoline's aromatic ingredients in compliance with evaporative emissions regulations. Ethanol is not the reason for that. Dumbed-down gas is.
Those who perpetuate the "ethanol myth" don't understand the technology, don't know the history, and aren't aware of the forces at work in the powersports industry. It is not true that today's oxygenated fuels are demonstrably harmful to either carburetor durability or carburetor function. Good fuels and good people are being unjustly maligned due to this nonsense. It's time this myth was busted and reason was brought to bear.
1. Los Angeles Trade-Technical College.
2. During which time my most popular class was training in carburetor theory.
3. I created the dealer training for the superlative 325-hp supercharged Ninja H2.
4. In almost 11 years with Kawasaki corporate I met regularly with my counterparts at the Big Four and other brands: networking, trading ideas, and studying best practices.
5. Yes, all production street vehicles are made slightly rich, for the reasons described.
6. It's no secret I intensely disrespect Internet powersports information enclaves. They're ruining the industry, taking what for me has been a pleasurable, memorable, rewarding pursuit leading to a lifetime of working with motorcycles and their riders, helping them, building relationships with them (one of my customers was a groomsman at my wedding), and turning it into a completely different, awful, alien thing; a darkly misleading black-robed secret handshake community self-servingly disseminating opinion as fact and by that failing to help, and actually hurting, members of our fraternity who need and deserve better.
7. Later, computerized vehicles do not lean out in the presence of ethanol because their fuel and ignition systems self-adjust, compensating for the added oxygen, producing a zero net effect on the engine. Thus to late model vehicles oxygenated fuel is invisible; unnoticed. As planned.
8. Ethanol-ized gasoline shouldn't be confused with alcohol as a fuel. I know something about alcohol-fueled racing carburetors. In addition to teaching jetting formulas for alcohol (sling psychrometer, anyone?) I did some work on mini-sprint cars, racers powered by motorcycle engines often run on 100 percent alcohol. The effects of straight (100 percent) alcohol on aluminum carburetors are astonishingly severe and unforgetable. But this has little corelation to gasoline with alcohol added.
9. Though why they feel boats is in their domain is beyond me.
10. Zinc-rich aluminum alloy flows easier when production casting. It was used originally because casting molds were at first not very sophisticated, and continued to be used by smaller and less-sophisticated manufacturers even after the emergence of higher quality alloys. I suspect Honda continued using the technology purely from inertia.
11. I alter jetting on one carburetor I rebuild to proactively overcome what I know is typically low cylinder compression on that model motorcycle. When I do that I am supplementing the factory's built-in richness margin. And it works. However, if I know the engine is getting a new top end, I stand down; I don't change the circuit. It's needed and effective only when something is wrong with the engine. Work this principle backward and you'll understand the ethanol issue.
12. Pro techs know to shrink float bowl gaskets back down in cold soapy water should the gaskets stand in fuel for any period of time (as when rejetting a bike on the dyno). A common practice that forums ignore.
13. Kawasaki owner's manuals say three weeks. They also address oxygenated fuel percentages the Kawasaki factory deems safe in its products. The OEMs therefore officially confirm that gas gels rapidly, and more importantly, that they aren't alarmed by ethanol.
14. Remember how gasoline used to smell? Like model glue. Gasoline's aromatics were removed for health reasons and in response to evaporative emissions legislation. Three weeks in some cases (and this is documented) is all you can hope for with these preservatives being absent in the gas now.