The Truth About Two Strokes And Four Strokes

by Nik
(Yucaipa CA, USA)

First off let me say there are way too many misconceptions regarding the debate on two vs four stroke, and most people base their idea of that particular engine on a single bike they have ridden.

The engine characteristics of two and four strokes are based solely on the way the engine was designed and tuned to use, that's it. One is not advantageous over the other in that respect. Both can be built and tuned to have whatever powering traits you want, except for the fact that two strokes produce more power per displacement.

What we're seeing in modern two stroke engines in dirt bikes is probably more like late 1980's early 90's technology, very few changes have occurred since then. So essentially what you're seeing today is yesterdays technology in 2-strokes being pitted against modern technology 4-strokes with hundreds of millions of R&D testing and promoting etc.

Almost every disadvantage found in 2-stroke dirt bikes today is because of the negligence in development. The technology is there to make 2-strokes put out as little emissions as 4-strokes if not less, just as well as getting rid of mixing gas and adding conventional oil sumps, oil pumps and full pressure fed lubrication systems to get rid of burning oil. Even things like EFI are very available.

As you can see the debate between 2 and 4 stroke really boils down to which one is funded and developed the most. But the real question is why didn't the four big manufactures take this route and develop 2-strokes? In my opinion the big bike manufactures saw the benefits of 4-strokes early on, probably in the early 90's. They knew emissions and oil consumption would pose a threat to 2-strokes - pretty much all the MX bikes in their lines - and that they didn't have the technology at the time to overcome that.

Also, I think they realized the benefits to be had by developing better 4-stroke engines to increase profits. If you look at the cost of comparable models from the early 2000's to now you will see bikes cost on average around at least $2000 more MSRP and require much more maintenance. This was no mistake that the big 4 had to suddenly stop producing 2-strokes because of emissions or some other BS. They were probably planning to phase out two strokes and only develop 4-strokes 10 years before we first heard about it. That's why from the early 1990's to now (with exceptions) you didn't see hardly any two stroke development worth mentioning. Even now when the technology is obviously there to tune up two strokes you see companies like Honda saying they will never sell another two stroke ever because it's a green issue? That tells you right there whats on their mind.. $$$.

The new four strokes are nice bikes but I feel two strokes have better potential if the same time, money & effort was put into them. They do have a better power to displacement advantage since a 2-stroke fires once every other stroke and a four stroke only once every four strokes. A 2-stroke if designed correctly could have more torquey, usable power and be faster. It's just a matter of the big four giving people what they want instead of forcing people to ride four strokes - and I say forced because it's not really a choice if you want to be competitive. Not to mention all big four companies will take all their bikes off the track if one independent team tries to ride a 2-stroke at any AMA event. It's kinda like price fixing in my opinion by neglecting two strokes so people will spend more money on four's.

Long live the two strokes!

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May 09, 2013
Emmissions From 2 Stroke
by: Anonymous

I think emissions are a big issue for 2 strokes and it's not really about burning oil, it's about not burning the gasoline. Emitting raw gasoline out the exhaust is a real issue and not easily solved. But Bimota and orbital and have solved this issue with direct injection.

It is great technology but requires high pressure fuel pumps, batteries, injectors which would have made the 2 stroke more expensive and heaver than a 4 stroke.

Honda probably went the 4 stroke route due to there user friendliness.


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