What Killed the Two-Stroke Motocross Bike and What May Bring it Back

The two-stroke motocross bike is all but dead. The epic staple of the motocross industry from decades ago is now an aging relic. The trademark br-a-a-a-a-a-a-a-p of a properly tuned 125cc two-stroke motocross bike is now a rarity, and the four-strokes have already begun their assault on the mini bike classes.

2 Stroke Motocros

The fact that two-strokes are quickly becoming an antique in the motocross world is undeniable. But what exactly killed this ingenious technology? Two-strokes are lighter, faster (at the same displacement), cheaper to buy and maintain, and easier to work on. On paper they are a clear victor over the louder, heavier, more expensive and more complicated four-strokes. So, what exactly is responsible for the demise of the two-stroke?

Racing Organizations (AMA/FIM)

AMA Motocross
Is the Racing organisation AMA or FIM responsible for the downfall of 2 Strokes?


When the four-stroke was first introduced, it was a joke. Heavy, expensive, loud and slow. Riding one was more of a way to make a statement about your personality than to actually ride the best bike available. So, racing organizations such as the AMA and FIM felt it necessary to give them a (huge) handicap. Almost double displacement for Motocross/Supercross class and exactly twice the displacement for the Lites classes. At the time this felt like a sensible move. The newer technology needed the extra motor size in order to even be remotely competitive.

The problem with the assumption by the AMA and FIM that the four-strokes are slower by nature is that it is wrong. Sure, you can make an argument that the piston travels four time as far for one revolution, but in practice, four-strokes can produce almost the same amount of power as an equally displaced two-stroke. As technology has evolved, the twice as large four-stroke engines have rocketed ahead of two-strokes, making two-strokes too slow for serious competition in the pro or national amateur levels.

Pro Riders

Pro riders are partially responsible for the death of the two-stroke like Chad Reed or James Stewart
Are pro-riders also responsible for the 2 Stroke demise?

While it is not really the pros fault that they have all moved to four-strokes, they are largely responsible for the demise of two-strokes in public opinion. Whether they switched due to corporate pressure or just because four-strokes are faster, the end result is the same: all pro riders now ride four-strokes.

This rather quick and unanimous change of preference had a lasting effect on public opinion. While 250 two-strokes were once cutting edge, they started to look outdated. Ricky wasn’t riding one, Kevin wasn’t riding one, why should I be riding one? Local pros and amateurs who wanted the latest and greatest were drawn by the technologically advanced four-strokes and thus made the switch along with Ricky, Kevin, Chad, and eventually James.

While it is impossible to blame the pro riders for their switch, they had to do it to stay competitive, the truth is that the decision by many and eventually all of the professional motocross riders to ride four-strokes had long lasting effects on the public opinion on four-stroke vs. two-stroke.



At first, the four-stroke was great for the manufacturers. They could treat it as a little pet project, and still make a sizable profit of it. It allowed them to explore the upcoming technologies while still making progress on their flag-ship two-strokes. However, as the four-stroke gained popularity, manufacturers such as Honda, Yamaha, Suzuki, Kawasaki and KTM were faced with a tough decision. Economically, they could not feasible keep producing and innovating on both the four-stroke and two-stroke platforms. Furthermore, it did not make sense for them to keep producing two essentially competing products. They had to make a choice, and they choose four-strokes.

Ever since the manufacturers have chosen the four-stroke as their priority in R&D, the two-strokes have only fallen further behind. Most remain unchanged year to year, and thus there is even more motivation for riders to switch to four-strokes. Even chassis and control changes which could be fitted to two-strokes largely do not, simply because the manufacturers have moved away from the platform as a whole.

Vet Riders

At first, the four-stroke was a vet riders dream. They were so much easier to ride, the extra weight didn’t really affect their riding style much, and the price was not an issue as most vet riders are well off financially. Obviously, the vet market is where the four-strokes first took off. They blew up among 40 and 50 year old motocross riders, and the whole movement essentially rode on their backs. Once the younger and more competitive riders saw how the four-strokes complimented the laid back riding style of the vet riders, they instantly wanted to jump on the four-stroke bandwagon. Once this movement began, it couldn’t be stopped, and hasn’t even now.

Will They Be Resurrected?

Will the bad economy resurrect the 2 Stroke world like it did in the 1970's?
Will the bad economy resurrect the 2 Stroke?

Our economy is in rough shape. There is no denying that the motocross industry will take a big hit in the upcoming months as gas prices ride, stock prices fall and jobs are lost. The motocross industry will not be exempt from these hardships.

As a result, dedicated motocross racers everywhere will have to make sacrifices in order to keep racing. One of these sacrifices, I believe will come in changing back to two-strokes. Two-strokes are cheaper to buy, maintain, and modify. Because of this, frugal riders will be more than willing to sacrifice some power and rideability in order to keep racing economically.

What Does the Future Hold

The future of motocross is in electric motocross bikes, such as the Zero or Brammo.
Brammo electric motorcycle


The future of the entire motocross industry is currently unknown. If we are able even to survive the upcoming economic crisis, what will our world be like on the other side? Will motocross still be even remotely popular? We may not know for 10 maybe 20 years what our future will hold.

Furthermore, does the four-stroke/two-stroke debate even matter if our future is clearly in green energy technologies?

While I do believe that greener motocross bikes, maybe even electric or solar powered will one day “rule the roost,” I also believe that in the short term, the dominant technology will depend on the economy. If the economy worsens, I strongly believe that two-strokes will end up on top due to their cheaper price in general. On the other hand, if gas prices continue to fall and our economy turns itself around, then four-strokes may stay on top.

The bottom line is that the reign of the four-stroke is destined to be short lived. Their rise was artificially supported by political and economic motives and thus they will soon be replaced by either green technologies, or fall to the cheaper two-strokes.

I would like to send a shout out to Eric Richards for giving me the idea for this post in a comment he left on one of my blog posts.

37 thoughts on “What Killed the Two-Stroke Motocross Bike and What May Bring it Back”

  1. I somewhat agree, and from a green stand point if you can work a measuring jug, that is the polution ratio of your two stroke eg: 50:1 on the other hand your four stroke a little bit down the road perhaps the scraper rings could and probably will be passing oil, the valve stem oil seals could be leaking. All this because the majority of people are scared to touch this strange machine or can’t afford it.
    Interesting thing is now how do you measure a bike like this, on the other hand buddy with the measuring jug is still at the same ratio 50:1, also remember both these technologies burned fossil fuels in the first place. Oh! and lets not talk noise polution.

    1. they said the four stroke was faster than the 2.. no duh? they dont even race them evenly..
      2stroke all day
      “if you wanna haul ass, you gotta mix the gas”

  2. I’ve never know a 4t that didn’t need regular topping-up, including the hyper-well-maintained Honda XL420 Yoshimura/Bell/HVA MX special I unfortunately rode for a while, late 70’s. Despite the huge cost it was slower than a standard HVA 250, ok? The old oil was used to oil the chain and stuff, but even that wound up in nature, not recycled. So, in my view, my 2t HVA’s didn’t use more oil than a 4t, nor pollute any more, just in another way. And the 2t’s were very frugal in parts, in comparison; pistons/rings/oil-seals occasionally, the cranks and bores lasted 3 years before being, begrudgingly, updated. I’ve worked out they ran for 25,000kms of racing and practice. Each. Long live petroil! The future is 2t MX, technology now allows 2t’s to run on digital injection and we’ve had 2t oil-pumps for years. Modern Evinrude 2t-outboards are, in fact, cleaner then most 4t-outboards! Thanks to digital injection. Interesting point: would such an injection-equipped MX-engine need an expansion-chamber? I firmly believe the 2t is the best engine for MX, the power-delivery and feel perfect to help you attain low lap-times. 2t rear-wheel braking was never an issue, it never caused any problems and you were always hard on the throttle before the bends anyway – my Honda 4t almost threw you over the bars every time you even inadvertently eased the throttle, anytime, anywhere! Very tiring to ride. Racing is about energy-management, and using energy trying to avoid closing the throttle is a no-no, that misuse of energy could loose you a race. And you can’t (in my day, at least) race a 4t full-bore all the time, like a 125 2t. Tends to tangle valves, old chap. Expensive. Same circumstances a 2t would sneer at you for being a wally not able to keep up. I feel the market will reign, and 4t’s will dissappear… again.

  3. If any of you guys are really interested in saving the 2 stroke. Here is your chance. By the way, do not disrespect them. This is to give them your opinion and to help them know we are out here and we are still strong. Please know that Roy Janson does feel the same way as we do. I know DC feels the same way as we do. So again, be nice and thorough but courteous. Through deduction, hopefully these are the emails needed. Good luck and long live the 2 stroke.

    President CEO of AMA Rob Dingman email: [email protected]
    President CEO of Pro AMA Roger Edmondson email: [email protected]
    Roy Janson email: [email protected]

    All other board members are probably with just the address. so first initial plus last name, then @

    AMA Board of Directors
    Stan Simpson, Chairman
    413 FM 1103
    Cibolo, TX 7808-1028
    South Central Region
    Term expires February 2012

    Jon-Erik Burleson, Assistant Treasurer
    38429 Innovation Ct.
    Murrietta, CA 92563
    KTM North America
    Term expires February 2009

    Jim Williams, Vice Chairman
    9950 Jeronimo Rd.
    Irvine, CA 92618-2084
    Kawasaki Motors Corporation
    Term expires February 2010

    John Ulrich, Member, Executive Committee
    581-C Birch St.
    Lake Elsinore, CA 92530
    Roadracing World Publishing, Inc.
    Term expires February 2009

    Erik Buell
    2799 Buell Dr.
    East Troy, WI 53120
    Buell Motorcycle Company
    Term expires February 2010

    Andy Goldfine
    8 S. 18th Ave., West
    Duluth, MN 55806
    Term expires February 2011

    Charles Goman
    PO Box 81
    Winder, GA 30680
    Southeast Region
    Term expires February 2012

    Perry King
    c/o AMA
    13515 Yarmouth Dr.
    Pickerington, OH 43147
    Northwest Region
    Term expires February 2010

    Michael Lock
    10443 Bandley Dr.
    Cupertino, CA 95014
    Ducati North America
    Term expires February 2011

    Arthur More
    16153 Starlight Dr.
    Surprise, AZ 85374
    Southwest Region
    Term expires February 2011

    Bill Werner, Assistant Secretary
    18405 Davidson Dr.
    Brookfield, WI 53045
    North Central Region
    Term expires February 2010

    Maggie McNally
    114 Kent St.
    Albany, NY 12206
    Northeast Region

  4. i agree on exactly what is said in the top about having to double the amont of engine displacement to even be competitive with the displacement of a 2 stroke in my opinion i think 4 strokes are a joke why would you want a heavier louder more expensive bike i do not think that 2 strokes produce more green house emissions when the 4 strokes have more parts in the engine that can be blown out or the exhaust just because they blow a few puffs of smoke and how can you not think it would just be the oil in the fuel that puts a die in the emissions that you can see and the four strokes just blow shit loads of smoke when valves are shot

  5. I’ve always been on a 2 stroke, started out on a KX125 and now ride CR250 but will need a new bike and I’m buying a 2 stroke. To me motocross is all about the 2 stroke, nothing beats the sound and feeling of being on a 2 stroke, and I’m doing just fine keeping up with the 4 stroke 450’s on my trak, and I’m on a 250. Not to mention I can easely fix my bike myself, no complicated valves or fuel problems, I know I feel sorry for my local deal for not bringing my bike in as often as my 4 stroke frinds.

  6. It is my opinion that the powers at AMA assumed some day that the bureaucrats would come down on them for having dirty running vehicles. They feared some sort of regulation, so they attempted to govern them selves. As far as emissions go, the government is not worried about the smoke, which is particulate matter being released into the air. No they are concerned more about the hydrocarbons, or unburnt gasoline, that has a more negative effect on our health than does particulate matter that we can see. As for the amount of hydrocarbons a single cylinder motorcycle motor releases into the environment pails in comparison to a sport like NASCAR, or even Indy cars or Formula 1. I even heard a NASCAR driver say that the government wasn’t much concerned about closed course racing, for the amount of hydrocarbon released by theses sports, pails in comparison to what our everyday driving releases into the environment. Even heating and/or cooling and lighting out buildings puts more green house gasses and hydrocarbons than our fossil fuels powered motor sports. With the advent of direct injection, and blue coating and treating heavy wear engine parts, along with 200:1 gas oil mixtures, two strokes will be back, but these new technologies applied will not be cheap. I see a great future for the beloved two stroke. Be encouraged my two stroke liking friends, the four strokes will be short lived, much shorter than when they went out the first time.

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  8. if only somebody could convince a pro rider to switch too a 2 stroke maybe the whole band wagon thing would turn around but even now the mini class has 4ts in it wich is one thing i thought id never see

  9. Though I grew up listening to 2 strokes through my youth and teen years (generally trying to hide and evade the bullies riding them), I will honestly say I never rode one. My first bike was(is) an 06 WR450. I was attracted to the low end torque, the full length power band, and the sound over the 2 stroke options I had available to me. I suppose that’s my personality coming through. I’m a back woods forager and I love push button starting, something 2 strokes aren’t known for.

    In reading this article, I would give a 2 stroke a try to see if I liked it with no preconceptions.

  10. Sir, while i agree with SOME of your assessment, how can you say that a 4 stroke makes more power. One only has to look at horsepower numbers. A 250f makes around 37, a 250 2 stroke makes close to 50. Check it out for yourself OR look at a MotoGP 125 single cylinder 2 stroke, it makes almost 60 horse. What 125, 250, or 450 naturally aspirated 4 stroke single makes that much horsepower? I’ll save you the time to look, not ONE. Not ONE!!!!!! A 250 MotoGP bike from last year enforces this, it made 115 to 120 horse. I am sorry, but you are incorrect. If 4 strokes are superior, why do they need a double displacement advantage and why did Honda say, if they ever show up at a National race, either SX or MX and there is a 250 2 stroke in the 250 class, they would leave and take all of their millions of dollars with them. Doesn’t sound like they have a superior winner to me, how about you? I’m sorry if I am coming across as rude sounding, I just get tired of all the mis-information and untruths being told to the unsuspecting public, who inevitably follow the crowd. Where’s the rebels, where’s the guy who used to put a 4 stroke in mX when the rules were fair and it stood 0 chance against the superior 2 strokes? But he did it anyway, cause he was a rebel? Are we ALL just followers and Kool-Aid drinkers?

  11. we cant all have 2 strokes because the chinese will start making them for 2k and “e” direct injected. next minute paying 14k will sound rediculous. 2 strokes are the “under wraps future” that everyone with a bit of an embarrased look on a 4 will have to throw another 14k at when the chinese are in no position to produce one.

  12. so im not exactly smart when it comes to these things as im new to motors in general but am i correct in understanding a 4 stroke needs to be about double the size of a 2 stroke in order to produce a competitive amount of power?

    if so i can’t see why anyone would want to use a 4 stroke, wouldn’t just using a more powerful 2 stroke be more efficient while granting the same or more power?

    and which actually produces more green house gases a 2 stroke set up or a 4 stroke set up of similar size?

    i don’t ride dirt bikes but im working on a motorized bicycle and went with a 66cc 2 stroke since it seemed to offer a good amount of power at an awesome price compared to any 4 stroke engine i could compare to it.


  13. I would like just to say 4t,s are crape thay brak your looking at scrap at a 1000 pound for a rebuild were 2t,s are mor 3-400 maybey 500 max as for raceing i stillrace my 89 kx250 2t and just 4 munth ago i came 4th yes fourth and their was only 1 other 2t their wich placed 17th out of 38 I here all the time 4t,s more power yes sure thay have alittle more and you hardly ride the bike and all 2t,s can easy keep up and have more fun on them as you practicing have to fight to taime them i love wrestling with my bike and will never turn to 4t,s come on 2t,s good old engineering show crappy 4t,s what you got

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  14. 2 stroke woods rider here. i’m ok with 4 strokes in professional level MX/SX…but it’s insane that the AMA has (quickly) removed 2 strokes from these events. the competition would be waaaay more intense if they let the 2t’s back in. SIGN THE PETITION!

  15. 2 strokes are motocross. To say the 4t’s are more powerful is inaccurate to this application. Maybe on a dyno, but not on the track. There are riders that can produce a faster lap time on a 4 vs a 2t, and visa versa. The power-band is so different between the two, it’s really upto the rider.

    I hate those heavy ass, hard starting four strokes. If you want cross country torque and a bike that will cruise across the crud…get a KX500.

  16. Every old school motocrosser knows that four-strokes are total dogs! The only reason we see them is this ridiculous politically correct AMA rule! Bunch of crap! The polution or “green” issue with competitive motorcycle racing is ubsurd! One old four stroke lawnmower running for an hour wipes out four motocross bikes racing (four or two stroke). Really…? Why are we talking about “green” with the very small amount of activity that motocross racing acounts for? I don’t get it whatsoever! Bring back the two-stroke for the love of god and country! They’re just plain better race bikes. Four-strokes have had their little time with a rules “heyday”. Too expensive to maintain, and boring as heck to ride. An entire generation of mx riders are learning a new sport: sucky, boring, uncompetitive crap. Call your AMA and tell them you are sick of their arbitrary old (now) rule! We want our sport back. Pleeez!

  17. What year did manufactures switch over to 4 stroke? I’m looking to buy the latest model used quad that is 2 stroke. Can anyone help me? I grew up riding a screaming engine and and I hate 4 strokes

  18. Nice thoughts and facts, I’m 40 in my prime I raced an rm 250 in the acu expert class when the lumber some yz426 came out, we all changed to four stroke.
    The guy who sponcered me at Wakefield off road told I would be slow on the 426 but I wasn’t , I was winning and loving it until I realised everyone else was on 426,s and good old Roy timed me, yes I was winning but I was 11 seconds a lap slower than when I was on the rm, long live the 2 stroke , I’m making another come back in the Eco class and catch me if you can on a 1989 rm 250 ha ha

  19. Being a motocrosser/ off road rider in the 70’s and still doing it today I started on two strokes, have owned four strokes, which are now no longer occupying space in my garage. I wonder how far two stroke technology would have come had not most of the manufacturers had not jumped on the four stroke bandwagon. Also if the fours are so much better than the two’s why limit the displacement of the two strokes in AMA pro classes. let them race heads up and see which rider can handle what. I won’t be flippant here and ask “do real motorcycles have camshafts?” that should state where I stand.

  20. I own 97 cr 500 99 rm 250 02 mxc 400 .. The KTM sits i ride my 2 strokes .. Love them will never give them up.. 2 stoke all the way.. Will never buy another heavy 4 stroke money pit….

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