2 stroke technology as compared to 4 stroke

[Ghostv2]

You forgot the most important part. Two strokes are fun as hell to ride!!!

That's anything with a motor.

[RubberSalt]

you forgot the most important part. Two strokes are fun as hell to ride!!!

bbbrraaaaaaaappppp!!!!!

[TwiZ]

This is a cool thread. Besides weed eaters and my huskuvarna and homolite chainsaws the only 2 smokers i ever owned was a old kx400. I was like 15 yrs old,cant remember the year but the exaust ran down below the frame and had dual shocks in the rear and it was freakin turbo fast,but never been much for bikes so i sold it. About 6 months ago i got a polaris 250 trailblazer that needed work for $300. I put new rings and bottem end bearings and seals,rebuilt carb and put a different primary clutch with heavier weights to make low end better along with a 11 t front sprocket,engine as basic as it gets,its abit of a turd, i bought it for my girlfriends son and its perfect for a 12yr old,and has proven to be very reliable.It will use 2-3 gallons of fuel (plus the cost of mix oil at $10 a quart) compared to my X using about half gallon to a gallon tops. Any of my friends that ride their 250 R or dirt bikes usually gotta break off early because they run out of fuel after a couple hours. Ive always prefered a 4 stroke,love the sound,for the trails we run you can lug em down where a smoker is in and out onthe clutch. So for me and where and how we ride i prefer a 4 stroke. I do have a question for the two smoke guys...would the polaris benefit from a pipe to get a lil more snot out of it,basically is the cost worth the gain?

[Mosh]

I personally have no interests in the 4 stroke versus 2 stroke category, as each has their own merits. and call me an old fart resistant to accept any new changes, but as being a professional auto tech and mechanic for almost 30 years, there are some designs that just never will be as bulletproof reliable and easier to squeeze power out of as back in the days of old. Personally, there is really not much room for improvement on a 250R engine, banshee engine, or even rock solid blaster engines and the like. sure, there are ways to bolster more power and efficiency, but usually that comes with a sacrifice of dependability.

I personally have seen some bone stock 250R blaster, banshee and older air cooled 4 stroke, engines be opened up for the first time in over 30 years in some cases. I personally have gotten over 10 years on some of these engine configurations without a rebuild. The same could be said for the old 300/250x 4 strokes and XR based 4 stroke engines.
While their is light years in improvements in power, weight reduction, etc, with newer designs, personally I don't feel many things are built near as well as what we have seen in the years past. And that is not limited to just ATV's. You can have all the technology in the world pushed into something, but when the raw materials are a fraction what they used to be in quality from decades ago, stuff just does not last, nor is it near as rebuildable as older stuff is.
The days of us seeing washing machines, small blocks, atv's and other items rolling off the line and still pumping after 20-30 years with limited service, are gone.

[RamsesRibb]

As far as the rule of thumb about a 4 stroke needing double the displacement to match the power output of a 2 stroke I think that’s outdated info. A modern 250-F race bike makes more power than a 125 pinger and a 450-F race engine will tear the decals off a 250 two stroke as it wheelies past it. Reliability and cost be damned, modern race four strokes are impressive beasts.

I don't think that is a fair comparison. You said yourself that your KTM300 was outputting more HP than the comparative 450 at the time of manufacture. I dare say that more energy and research has been placed into the current crop of 450 racers pushing it to a new pinnacle. That doesn't mean that equal increases are not possible on the 250 2strokes. I just finished watching endurocross and it appears as though even on a tight ultra technical track the two stroke bikes are easily capable of winning over 4 strokers. I'll bet that most of the focus to superiority of 4 stroke bikes was purposeful when the factories pushed their new products in the 90's. More money to make from parts is my guess.

On a side note, I don't know how common knowledge this is, but Mr Soichiro Honda despised the 2 stroke engines that he was manufacturing because of the noise and smell. I wonder if that belief was passed down?

[RamsesRibb]

I personally have no interests in the 4 stroke versus 2 stroke category, as each has their own merits. and call me an old fart resistant to accept any new changes, but as being a professional auto tech and mechanic for almost 30 years, there are some designs that just never will be as bulletproof reliable and easier to squeeze power out of as back in the days of old. Personally, there is really not much room for improvement on a 250R engine, banshee engine, or even rock solid blaster engines and the like. sure, there are ways to bolster more power and efficiency, but usually that comes with a sacrifice of dependability.

I personally have seen some bone stock 250R blaster, banshee and older air cooled 4 stroke, engines be opened up for the first time in over 30 years in some cases. I personally have gotten over 10 years on some of these engine configurations without a rebuild. The same could be said for the old 300/250x 4 strokes and XR based 4 stroke engines.
While their is light years in improvements in power, weight reduction, etc, with newer designs, personally I don't feel many things are built near as well as what we have seen in the years past. And that is not limited to just ATV's. You can have all the technology in the world pushed into something, but when the raw materials are a fraction what they used to be in quality from decades ago, stuff just does not last, nor is it near as rebuildable as older stuff is.
The days of us seeing washing machines, small blocks, atv's and other items rolling off the line and still pumping after 20-30 years with limited service, are gone.

I agree with the reliability issue. I have a stock 1980 ATC110 which is still running ok. It leaks all over but no smoke and still has good power. I also had a 185S which was never opened up as long as I had it which would be early 2000's. Same with my dads 93 Fourtrax 350. I had to did a rat next out of the air box but never had to open the engine.

That being said, this thread is not really a which is better match. I meant it to be informative about the research and development of this technology and just a current state of the industry. I don't believe we are getting all that is possible concerning 2 stroke technology.

[RIDE-RED 250r]

We might not be getting all that is possible in 2-stroke tech in dirt bike and ATV world, but other industries previously mentioned absolutely are. ETEC direct injection, stratoported chainsaws being top on the list.

[RubberSalt]

We're building better machines, but pushing them very hard. If we built our 450s with the quality of metal from the 80s, there a good chance the life span would be cut by atleast 30%. It isn't the quality, it the level of stress were pushing on them.

The 350x was around 26hp. But the 450r is around 46hp. Thats ~76% more power and only a 28% bigger motor. Get a 350x to push around 36HP and see how long it last. On pump gas!

[El Camexican]

I don't think that is a fair comparison. You said yourself that your KTM300 was outputting more HP than the comparative 450 at the time of manufacture. I dare say that more energy and research has been placed into the current crop of 450 racers pushing it to a new pinnacle. That doesn't mean that equal increases are not possible on the 250 2strokes. I just finished watching endurocross and it appears as though even on a tight ultra technical track the two stroke bikes are easily capable of winning over 4 strokers. I'll bet that most of the focus to superiority of 4 stroke bikes was purposeful when the factories pushed their new products in the 90's. More money to make from parts is my guess.

On a side note, I don't know how common knowledge this is, but Mr Soichiro Honda despised the 2 stroke engines that he was manufacturing because of the noise and smell. I wonder if that belief was passed down?

What’s not fair? Both examples were EXC models (Enduro X Country) and both were considered to be the pinnacle of technology for that class back in the day. Or better put, if I were to trade my 300 for a 4 stroke that bike would be the closest thing to a direct swap.

Fast forward a little more than a decade and the 300 now makes about 16% more power with an even smoother power band and the 450 enduro claims 20% more hp. The 2 stroke still spanks the enduro line of 4 stroke bikes, but it’s no match for the 450SX and it doesn’t need to be. The 300 has more than enough jamb for an enduro bike and so does the tamer EXC version of the two 4 strokes mentioned. I doubt we’ll ever see another 500cc 2 stroke mass produced. Very few riders could handle them back them, even some factory riders were detuning them, so what’s the point? Even KTM realized the 380 was overkill back in 2002 when they dropped it.

I have no idea what drove the Japanese manufactures to the 4 strokes, but I’m guessing it was a combination of all the PC correct global warming hype and the opportunity to cut the cost of R&D by putting all their attention on 4 strokes which make up all their street bikes, automotive affiliations, GP bikes, F1 programs etc. Keep in mind a lot of these companies work with others. The 5 valve engines from Yamaha and Toyota were a joint effort.

In the grand scheme of things snowmobiles and dirt bikes are a pretty small piece of the pie, but looking on the brighter side of things, the Big 4 stepping back from the smokers (and a strong yen) has allowed the Europeans to get into the game and build some pretty cool bikes. The more manufactures there are out there, the more innovation there will be.

[RamsesRibb]

I was referring to the 250 vs 450 comparison as not being equal footing. I inferred that your KTM comparison was a realistic comparison.

Also regarding the reliability of a 350x as compared to a modern 450, again totally unrelated but mostly due to the rotating mass and stresses created by the older designs more massive piston And less efficient timing system.

[BOB MARLIN]

To get back to the original topic, I had a boat with a modern 2 stroke outboard on it . It was a 225 Mercury "Optimax". It was direct injected and actually has an air compressor that was belt driven off the fly wheel that it used kinda like a blower on a car. The oil injector was computer controlled and could run as much as a 200:1 ratio. This engine would push my 26' off shore fishing boat well over 40 mph. It was quiet, sipped gas and was almost smokeless. I don't know what displacement it was but it was dyno'd at one of the shops I took it to and it put out just over 250 hp.

But the problem was that it was so "hi-tech" I just couldn't keep the thing running, and it was unreliable. When it ran, it ran fantastic, but it ended up spending so much time in the shop I had to get rid of it.

[RIDE-RED 250r]

I'm guessing they dynoed the Merc at the crank?? If so that makes perfect sense that it dynoed 250hp actual vs the advertised 225hp. Way back in the day, outboard motors were rated by crankshaft HP and sometime in the mid 80's they started rating by popshaft HP. So that's why it makes sense that your high tech modern Merc 225 was rated at 225hp (propshaft) and the actual dyno test showed 250 (at the crank). Sounds like about the right amount of loss from the power taking one 90 deg turn in the lower unit.. (If I'm correct in assuming they dynoed at the crankshaft)

Either way...interesting sounding outboard!