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Are 2-Strokes Making A Comeback?

Whenever I hear the words “two-stroke,” I immediately think of someone ripping it up on a good ol’ 125 dirt bike. I don’t know what it is, but the the sound of a finely-tuned two-stroke just gets me pumped.

Two-strokes will always rule in my mind because they’re just too blasted fun to ride, even if I have to ride one illegally someday because it’s “bad for the environment.”

Three 125 2 Strokes Are 2-Strokes Making A Comeback?
Which Flavor Do You Have?

For a number of, years four-strokes have totally dominated the motocross bike market, but something tells me that two-cycle dirt bikes are not done. There are still many ways to get more power and less pollution out of a two-stroke. Some of these have been in the works by the popular Austrian company KTM and the lesser known Italian motorcycle company of TM, as well as Maico International.

These two companies have been working on something that will for sure bring the two-smokers back on the podium. With the new technology they will be able to bring the pollution level down to that of the four-strokes, if not lower. This technology has been working on outboard boat motors for decades. My question is, “why hasn’t it already been put to use on motocross bikes?!”

This “new to dirt bike” technology is direct injection…. Instead of having a carburetor that inconsistently squirts the fuel into the reeds and the engine, direct injection will squirt the fuel “directly” into the cylinder of the two-stroke engine.

Once the timing of the injector is perfected, there will be hardly any unburned gases going out the exhaust because the injector will only spray the gas mixture when the exhaust ports are covered by the piston. This is will not only burn much cleaner, but it will increase torque throughout the entire RPM range. More torque = more traction = faster acceleration = faster than four-strokes.

There are other ways of bringing the two-strokes back, such as experimenting with cylinder porting, crankcase volume and shape, testing exhaust pipes with different shapes, angles and lengths, as well as making them lighter. Cylinder porting does depend on the rider, but if you want a screaming 125 like it should be, then porting for that can make a significant difference compared to stock 125’s today.

Pipe companies have put so many hours into testing pipes for 125’s it’s not even funny. Although you may hear that aftermarket pipes just change the power curve and don’t add horsepower, some companies have managed to squeeze more power out of the bikes as well, especially on the big-bore 125’s.

2-stroke dirt bike pre-mix
How Much Oil Do YOU Use?

Weight is another major issue that the big companies can perfect on their two-stroke motocross bikes. It’s pretty obvious that Yamaha has not done much to their two-strokes when their 250cc four-stroke motocross bike weighs five pounds less than their 250cc two-stroke. 

A four-stroke of the same displacement as a two-stroke should weigh more just because it has more parts. A light two-stroke would put a four-stroke out of its misery, especially if it has all of the above done to it.

It’s only a matter of time until two-strokes are booming again and we hear the sound of music at the tracks. The technology is here, it will just take one smart company to build and start another revolution of two-stroke dirt bikes…. Are you ready?


Tuesday 16th of October 2012

Please research Honda's relationship with the AMA to learn why 2-strokes have almost disappeared from motocross racing. It's about $$$$. Then educate you readers on Honda and the AMA.

Big Sven

Friday 2nd of July 2010

Well said, Sir!

Here in Europe we have 50cc mopeds with fuel-injection, so they pass the EPA tests, and all scooters and motorbikes have it now. You can't make and sell a new bike without it, no carb passes the test. You need oil-injection, though, and, surprisingly, it doesn't seem to harm the cat-converters some models also fit.

I raced MX in the 70's, mainly HVA 2-strokes, but the last was a 4-stroke. Big mistake. Fun to ride, yes, but a big mistake to RACE with. Spent a fortune on the Honda XL350 engine, converting to 420 and tuning it with all the USA goodies, in theory it punched-out 45 bhp, but I passed by old rattling 390 HVA's ridden by guys with half my experience! I never felt I could ride to the edge with it, it felt soggy, it didn't feel like a racing engine. The '78 HVA I'd built it into was great, thank god, for I stuffed the bike into the bends like a banshee to make up the time I was losing in spades elsewhere. Some riders loved 4-strokes, rode the wheels off them, fast, won races, but I never did.

Age, lack of money, injury (at work) stopped my racing, but I still regret selling my '76 Mag GP250 HVA 6-speed with Ohlins expansion chamber. Fastest, most reliable, best handling bike on the circuits ...and also the cheapest bike I ever ran, apart from a crash-damaged Gas Girling (the ONLY time in 3 years I crashed it, to avoid hitting another rider) I never had to replace anything other than standard wear-an'-tear, tyres, chains, pistons, rings, plugs, airfilters. Same crank for 3 years, never split the cases or touched the clutch (we never used them anyway). 25/1 petroil, gear and shift to grunt the engine, not rev, on full-throttle (hey, why bother closing it, huh, ploughboy?) simple gas-station 2-stroke oil (Shell 2T stuff for lawnmowers. Well, the HVA WAS a lawnmower on wheels!) jet the carb so the engine only begin to chime properly a quarter into the moto, and the bore just gets better with age, no blowby AT ALL.

"Those were the days, my friend, we thought they'd never end...."

But they do. So don't think - do it NOW. There IS no 'tomorrow'.

Kelley Fager

Friday 2nd of July 2010

Wow, that was a mouthful! Thanks for the comment! Sounds like you've had a long motocross history of two and four strokes. Hopefully someone will bring them back soon so Honda can eat their own words...