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Why are two strokes so uncommon


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  #1  
Old 05-27-2008, 09:25:48 PM
Mac Leod Mac Leod is offline
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Default Why are two strokes so uncommon

A while back I decided to direct my collection towards old two stroke engines, mostly because my space is limited. At this point I have found two Clintons and a few late Tecumseh/Power Products engines. Is there some reason it is so hard to find these old two stroke engines? If my collection was Fairbanks Morse engines I could have a barn full in a day. It is very rare to see any old two stroke for sale any where.

Any thoughts?

Mac Leod
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Old 05-27-2008, 11:00:04 PM
Tom G Tom G is offline
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Default Re: Why are two strokes so uncommon

"It is very rare to see any old two stroke for sale any where."

I see Maytags on this site, and on E-bay, all of the time.
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Old 05-27-2008, 11:01:46 PM
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Default Re: Why are two strokes so uncommon

well....I have been working with engines in general everysince i was 6....im 21 now....that makes 15 years...my findings through these years are that there not so common due to a fair amount of attention 2 cycles actually need. Having to take the time to measure out the correct amount of oil for each gallon of gas can become quite a hassle so it's easyer for the majority of people to go with 4 cycles....sure, they require maintenence to and they share there fair share of down time aswell, along with any other engine, but being capable of more then half of percentage of the year (BESIDES MAINTENENCE) of being able to just fill the tank with raw gasoline, pull the string or turn the key and go becomes more easy then to have to measure oil...mix it to the gallon of gas....being able to keep that constant ratio is more of a hassle then 4 stroke. But the 2 stroke and 4 stroke shair there ups and downs...i could go on all night about 2 and 4 stroke up's and downs but for now, im speaking of the regular, non oil injected, non pre measured, pre done by a pump, 2 cycles that the fuel has to be pre-mixed manually, and the 4 cycle. Also the 2 cycle runs at a mich higher RPM then the 4 stroke which makes the 2 stroke ware out quicker so the 2 stroke has to be "babyed" so to speak, to keep it well maintained and oiled, which is not so with a 4 cycle. Which makes 2 cycles actually a higher in maintenence engine, (in my opinion) reguardless of how much care you put into the 2 cycle engine. So that may have alot to do with why there not so popular from "yesteryear" Now today with all the tree huggers going around...they may tell you a slightly off key story to what i have just described....but i bet i hit the majority of it dead nut. This also comes from me as i use to run both 2 and 4 strokes..now i run strictly 4 stroke and an ocasional 2 stroke featherlite....so i know what im talking about..but as below in quota...R.M.V.

Sky

(results may vary)

Last edited by Sky; 05-28-2008 at 03:41:30 PM.
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Old 05-27-2008, 11:20:09 PM
smgussey smgussey is offline
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Smile Re: Why are two strokes so uncommon

The really simple two-strokes (port type) are less efficient than a comparable four stroke - although they are lighter than a comparable horsepower four stroke, this is why they ended up in snowmobiles. Another reason for them in snowmobiles is their throttle response - especially the reed valve engines (in my limited experience). Another used-to-be popular two-stroke would be the Detroit diesel engine, awesome sound with the supercharger going (this was their way of scavenging) and a straight pipe. Too loud, too messy, too inefficient to keep going, though.

Many two strokes SOUND like they are running faster due to the fact that every revolution there is a power stroke (more exhaust noise), where a four-cycle only hits on every other crankshaft revolution.

I'm not sure about the efficiency of the 2-stroke with the charging cylinder (like Reid), but I'm guessing that parasitic losses on that extra cylinder might hurt it.

Two-strokes have gone out of fashion as of late due to the inefficiency and their inability to meet emissions regulations due to the oil in the exhaust.

I'm working on reading Wendel's book "American Gasoline Engines" and he states several times that the farmers, etc. just didn't seem to take much interest in the two-stroke engines. I'm guessing that it may be due to the fact that few tractors came with them, and of course the famous Model T Ford did not have a two-stroke, nor did the Fordson tractor.

Personally, I would have thought a two-stroke would be good for a farmer back then who wasn't good as a mechanic as there are much fewer moving parts and less adjustments to go wrong.
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Old 05-28-2008, 04:08:45 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Why are two strokes so uncommon

There are several reasons that the 2 stroke did not really catch on in 'the old days'. At the time, economy of fuel usage and cost was an issue. A 2 stroke uses more fuel because it fires at every turn of the crank. The gain is that power is delivered more evenly. Cost of building the unit was also an issue. Although the 2 stroke is a simpler design, and has less moving parts, its machining requirements were different. It took longer to machine the cylinder and piston, due to porting timing, wether the piston was stepped or the ports themselves were timed. Most of the earlier closed crankcase 2 cycle engines had piston port intake. Later on rotary valve and reed valve intake systems appeared on smaller engines. Another turn off to owners was the exhaust noise. Listen to a QBA Fairmont, under a load, and you will tire rapidly of the loud exhaust! Even the venerable maytag can be a pesky noise maker if run without a muffler (which it shouldn't). Mixing oil and fuel was also an issue. Too much oil, you got a lot of smoke. Too little, you got a seizure, although for most of the older engines, let 'em cool, fix the mix, and run 'em, usually worked. Try running a modern 2 cycle without oil, and see how long it lasts 2 cycle engines have been around a while. for the most part though, they were lighter, and smaller than their 4 stroke counterparts, and they did not have the appeal of a hit and miss engine. They were passed by by most collecters, even the maytag engines were passed over a lot until recent years. I can remember not too long ago, paying $50 for a near running model 92, and complaining it was too high. what do you pay for one now?

I do have a bunch 2 stroke engines that missed the junk pile. A 1909 2 HP Detroit Engine Works, with low pressure fuel injection (ran a generater for a vaudville house in PA), a 1921 Unit Motor Co. 2 HP (one of 2 known, ran a water pump in upstate NY), A Jacobsen 4 acre reel mower (1927, still cuts good), as well as a few more modern Jakes (6 I think), A 5 HP 2 cylinder 1919 Arrow Motor Works/Pausin Engineering fire pump (Waterman K-2 engine), several Pacific Engineering fire pumps (have 3 of these, 1939 - 41 &42 with different engines - real screamers these - 9.7 HP @7800 RPM, 250# pressure @ 70GPM), and a 1950 Mall 7-H 2 man chain saw. There are still a lot of these engines out there, you just have to look harder to find them. As for oiling - the Fairmont QBA, the Pacific Engineering, and the Mall all take 12:1 oil ratio (3/4 cup oil to gallon gas. most others take 16:1, except the Detroit and the jake 4 acre, which use drip oilers for liquid oil intake. Just because an engine is 2 cycle, does not mean that it does not use liquid oil for lubrication. The Jacobsen 4 acre , the Detroit Engine Works, and the Pacific Engineering (both the Johnson and Evenrude engined units), and the Mall Saw, all depend on liquid oil in the crankcase. Their con rods actually have dippers on them to scoop the oil into the bearings. Most of these engines need a heavy base oil for lubrication, such as SAE 30 or 40 NON Detergent. Years age I had a Puch 'Twingle' made for Sears Roebuck. It was a 250 CC, and had 2 pistons and cylinders, and a common combustion chamber, fired with 2 plugs. This machine used a 16:1 oil ratio, with SAE 50 oil Smoked like a fool when cold, but when warmed up, nearly no smoke at all!

As far as wear and tear - some did wear out quickly. The lawn boy mowers were a prime example. The shop I worked at as a kid used to call them "2 and done mowers" 2 years that is. My Detroit has never been opened up, neither has the Mall, all 3 Pacific Engineering pumps, nor the QBA Fairmont. All the Jacobsens have never been opened either, and all are in excellant condition. As long as the proper oil ratio is used, the exhaust ports are cleaned as nescessary, and the cooling fins are kept clean, a 2 stroke probably will out last a 4 cycle. One word of advice here - I am talking about machinery made before approximately 1965. Anything built after that date probably has been built with 'Programmed Obsolescense' designed into the unit. P.O. meand that the unit is designed to fail within a designed time frame. This failure means you have to replace the unit at the end of that time. Like it or not, P.O is all around us today. Sears mowers have a designed time frame of 3 years. Within that time, either the plastic cam or governor inside the engine will wear out, or the ignition module will fail. Also, near the end of that period of time, unless you meticulousely clean off the inside of the mower deck, you will begin to see rust holes thru the deck. Most plastic parts will degrade. Other manufacturers have a similar time period built in as well. how long do you expect to keep your leaf blower or string trimmer? Running a 50:1 oil mix will practually guarentee 2 or 3 years is it. TORO does it one better, after 2 years, they alter the design of the machine, and then no longer make spares for the 'obsolete model'. I have a perfectly good string trimmer with one exception, The new alcoholized fuel has eaten the rubber gromet that seals the fuel lines to the plastic tank. That 25 cent part is no longer available, even though the machine is only 3 years young, due to their policy. Go figure!

If you look around, you will see a lot of 2 stroke equipment still out there. There arn't as many flywheel engines, but there are a few. Here are a few that come to mind, besides the ones already mentioned:, Gade Saws, Fairmont railway engines, Maytag - 72 twins, 82 & 92 horizontal singles, as well as a host of uprights, Jacobsen - made 2 stroke engines from the1920s into the early '70s, Clinton, Power Products (Later bought out by Techempseh), Johnson motor Co., and more. Can anyone name more oil burners?

One last note - The federal government means to phase out all 2 cycle engine production by 2010, due to air pollution concerns. They have already forced the motorcycle industry to cease production, and are now after lawn equipment manufacturers. Chain saws are the last to be phased out, possibly by 2011-12, and the manufacturers are scrambling to get a replacement engine on line in time.
Andrew
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Old 05-28-2008, 04:39:04 AM
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Default Re: Why are two strokes so uncommon

Lots of them over here in the UK and Europe, with makers like Villiers, ILO and others. We have an ILO-engined army generator with a 372cc two-stroke engine (22.5 cu ins) runs well but like most two-cycle engines it is uneven when running off-load. It is a pure stationary engine, not a modified snowmobile unit. They made hundreds of thousands before Rockwell/Tecumseh took them over and shut them down.

Possibly we had more utility devices like lawn mowers with two-strokes than in the USA, and in Europe there were also regular cars like DKW and SAAB with their own two-stroke engines in addition to the engines produced by Villiers for sale in small 3-wheelers in the UK.

Our Junkers that we are collection soon is a two-cycle diesel, and there were a fair few of those as well. The fact that it is an opposed-piston engine makes no odds, as you had those in the USA as well (Hill diesel for one, and Fairbanks-Morse and EMD in the larger engines)

I think that if you separate out the small, plain-bearing types like Maytags etc., and go the next step up in size and power, then they get quite interesting.

Peter
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Old 05-28-2008, 06:20:11 AM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Why are two strokes so uncommon

[QUOTE=Andrew Mackey;306270]
As far as wear and tear - some did wear out quickly. The lawn boy mowers were a prime example. The shop I worked at as a kid used to call them "2 and done mowers" 2 years that is.

My dad had a lawn mower and outboard sales and service. He rented lawn mowers, the only mower that would hold up in rental service was Lawnboy. We would mix the gas and oil and provide it with the rental. Never had a bent crankshaft,most B&S wouldn't go a month without bending one. I use a 1959 model Lawnboy every week for trimming, it was one my dad sold to a friend. He gave it to me in 1979, said it didn't run well. I cleaned the ports and fave been using it since, points and condesor changed twice, engine has never been apart. Marine engines were mostly 2 cycle because of the power to weight ratio.
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Old 05-28-2008, 06:37:10 AM
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Default Re: Why are two strokes so uncommon

I just picked up a little Power Products horizontal shaft engine at a show this weekend. Tank was clean, tingled the fingers on the plug when you turned it over by hand and, it was running on a prime before I left the show that afternoon. $20.00 invested. They are out there just waiting to be found, someone brought, and someone else went home with a barn fresh Jake 4 acre mower at the same show.
Peter
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Old 05-28-2008, 07:54:55 AM
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Craig DeShong Craig DeShong is offline
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Default Re: Why are two strokes so uncommon

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Originally Posted by Andrew Mackey View Post
There are several reasons that the 2 stroke . . . Andrew
Great post Andrew, thanks for all the information.
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Old 05-28-2008, 08:12:16 AM
smgussey smgussey is offline
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Smile Re: Why are two strokes so uncommon

Quote:
Originally Posted by Andrew Mackey View Post
As far as wear and tear - some did wear out quickly. The lawn boy mowers were a prime example. The shop I worked at as a kid used to call them "2 and done mowers" 2 years that is.
Andrew
I respecfully disagree. My Grandmother had a LawnBoy mower that I started using when I was 10 years old (and it was old then!). This mower was used until her house was sold a few years ago, at which time we gave it away to a friend who is still using it, I believe. I'm now 27 years old, so I know for sure that I used the mower about 15 years with no problems from the engine whatsoever. All I ever did was sharpen and replace blades.

Also, our Sears mower that gets used on the farm (read: somewhat tough life) is about five years old and still going strong with no problems whatsoever. Just a blade sharpening and replacement. Even the mower we got before that still works, just starts harder than the newer one - that one I would say is at least eight years old.

Also have a Yamaha riding mower, was bought in 1993 I think and I still use that as well. You guessed it, just sharpen and replace blades. Still original belt, tires, etc.

Mechanical devices need care, and many city people either don't know how or don't care to get their hands dirty with oil changes, filter cleanings, etc. Or even to blow the grass clippings out of the cooling fins from time to time. With proper care, these tools/engines can last a long time.

Andrew, you also mentioned that a Maytag shouldn't be run without a muffler... is there a specific reason why? Most stories I've heard from old timers talked about how the noise out the pipe was loud, and many videos on YouTube show them run without a muffler.
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Old 05-28-2008, 08:56:33 AM
K D Redd K D Redd is offline
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Default Re: Why are two strokes so uncommon

I too must disagree with Andrew. The weed trimmer I used is a MAC-80 which I bought at a yard sale over 10 years ago. I do not know how old it was when I bought it. I have used it every summer using Weedeater/Poulan 40 to 1 2 stroke oil to mix the fuel. I though it had bit the dust this spring. Running poorly. I took the carb apart and the alky fuel had attacked a flapper valve on the fuel pump diaphram which was replace but it still ran poorly. I was about to give-up on the trimmer but I changed the plug, the old one looked ok, and she was back running like she has for the last 10 years or more.

Kent
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Old 05-28-2008, 11:29:12 AM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Why are two strokes so uncommon

Mac leod; I just traded off a nice Jacobsen at Portland Then went out and bought a Johnson utilimotor. it's a hit & miss and runs just like a single Maytag. Aside form Maytags there a lot of great boat motors out there. Here some engines to look for Callie, Tuttle, Arrow. Other two cycles are , Sieverkropp,Vim,Bicknell,Aerothrust,Associated 3/4 HP,Elgin Halfhors,Villiers,Dodd(John Hume),Matchless(Wilson Machine Co.), Righter (Drone Engine). And yes I have all of these in my collection. I collect mostly fractional HP engines. It is interesting that when another collector ask me what I collect, they usually have no idea what I'm talking about. They are out there , you just have to look for them. Ron
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Old 05-28-2008, 03:30:58 PM
Jim Metzger Jim Metzger is offline
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Default Re: Why are two strokes so uncommon

I am a huge 2-cycle fan even though I am a Briggs collector.
It was actually Lawn Boy, Power Products & other early 2-cycle engines on walk behind rotary mowers built in the late 1940's and early 1950's that woke up Briggs, Clinton and Lauson and led them to develop a low cost light weight lawn mower engine. Up until that point these manufacturers were using a variation of their cast iron engines, which were very heavy compared to 2-cycle engines.
Consumer 2-cycle engines in many applications, in my opinion, offer many advantages over a comparable 4-cycle engine of similar HP. First off they are simplier with having no mechanical valve train to wear out or need attention. They have a power stroke, on every stroke over a 4-cycle engine, which usually means they make more power with less displacement. They are ideally suited to walk behind rotary mowers because their ideal rpm range is well suited to rotary mowers. I also think that not having a crankcase to maintain is a plus. Probably their main faults are that the user has to be accurate in the amount of oil they mix with the gasoline. Many users,with the more is better theory, are sloppy and do not do a good job with the correct gas/oil mixture and more times than not add way too much oil and then they will smoke and foul the spark plug and carbon up the exhaust port in a relatively short period of time. Then there are those that do not know the difference between 2 and 4 cycle engines and try to use regular gas with no oil and we all know what happens then.
Many, many two cycle engines have been scraped because an air leak occured and the engine started hard or if at all. Crankshaft seals leaking and or gasket leaks can cause these air leaks. Engines with reed petals that are borken also cause erratic performance. With the great synthetic oils we have today and the 50-1 and leaner mixing ratio's, 2-cycle and 4-cycle exhaust can look the same.
When I raced go karts it was not uncommon to achieve 2 and 3 HP per cubic inch on modified 2-cycle engines. It is still a thrill to hear a modified 2-cycle at full song in some kind of racing device whether it be a model plane or go kart.
2-cycles forever....
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Old 05-28-2008, 04:08:57 PM
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Default Re: Why are two strokes so uncommon

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Originally Posted by Jim Metzger View Post
When I raced go karts it was not uncommon to achieve 2 and 3 HP per cubic inch on modified 2-cycle engines. It is still a thrill to hear a modified 2-cycle at full song in some kind of racing device whether it be a model plane or go kart.
2-cycles forever....
On the Isle of Man, two-strokes had a very large part in the smaller claases, until the multi-cylinder Hondas came along in the early 1960's, in fact DKW were very competitive much earlier.

The East Germans did a huge amount if development, which was all to waste as the multicylinder Japanese bikes took over the whole race.

Also look up "Schnuerle", he did a lot of work on two-stroke porting.

Peter
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Old 05-28-2008, 10:06:43 PM
Mac Leod Mac Leod is offline
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Default Re: Why are two strokes so uncommon

So basically it sounds as though maintenance (or lack there of) did them in. I would really like to come up with a good collection of the two strokes engines made by Power Products and Tecumseh---sort of specialize in them. Unfortunatly they seem to be very uncommon, and for the few I found, they are almost all missing there mufflers . Does anyone out there collect Power Products engines as a main focus? How about two stroke engines?

Mac Leod
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Old 05-30-2008, 09:29:59 PM
Mac Leod Mac Leod is offline
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Default Re: Why are two strokes so uncommon

Well, an AH -47 showed up on my porch today ...in the form of a beat up Lombard chainsaw. The engine is in good shape though the saw is junk. Should get to it in a few days, after I finish my P/P AV-31 resto.

Mac Leod
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Old 06-05-2008, 02:40:34 AM
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Default Re: Why are two strokes so uncommon

Last week, Andrew Mackey posted:
".....Years age I had a Puch 'Twingle' made for Sears Roebuck. It was a 250 CC, and had 2 pistons and cylinders, and a common combustion chamber, fired with 2 plugs.....".

My dad had one of these in a 1966 Sears Allstate motorcycle. They (Steyer-Diamler-Puch) made 2 versions for Sears - A heavy 'cruiser' with full fenders, and a lighter model that would compare to a Honda scrambler (It wished!). Dad had the heavy one. I learned to ride on it and when I turned 16 & got my license, 'assumed' a majority shareholder status.
Through a series of cosmic alignments, I just today was able to re-acquire the engine from that bike. Not just one like it, but THE engine from that bike.
Here is a picture of it taken this afternoon.
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Old 06-05-2008, 10:35:15 AM
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Default Re: Why are two strokes so uncommon

Gentlemen...some excellent posts and commentary on two-stroke engines. Very interesting reading. Iíll throw in my $.02 as Iíve worked in the two-stroke engine field for most of my career.

I must say that my 1976 Lawn Boy two-stroke mower still runs perfectly and I still use it for trimming. Over the years Iíve replaced a bent crankshaft, ignition module, recoil starter spring, and one spark plug. The engine still has the original piston, rings, con rod, and bearings. It starts on one or two pulls and has adequate power for most mowing conditions. The secret to long life for one of these is to always mix fuel and oil correctly and use good two-stroke oil made for air-cooled engines. Husqvarna chain saw oil has an additive package thatís the best on the market for reducing carbon and varnish. I highly recommend it. But probably the best advice to keep a Lawn Boy running is to never lend it to your neighbor!

The carbureted two-stroke using crankcase compression for cylinder scavenging is mechanically the simplest form of internal combustion engine. However, thereís always some air/fuel mixture lost to the exhaust during the scavenging process Ė from 15% to 40% of the delivered charge, to be exact. This is what contributes to the high hydrocarbon emissions and reduced fuel economy when compared to a four-stroke. The fact that the engine produces a power stroke for every crankshaft revolution per cylinder means high power output per displacement and per engine weight. This coupled with the ability to run in any position makes them the preferred choice for a chainsaw engine. The high hp/weight advantage makes them particularly attractive for outboard motors and snowmobile applications. When an expansion chamber exhaust system is employed, the engine can easily produce twice the power output of a naturally aspirated four-stroke of equal displacement. The expansion chamber harnesses the exhaust pressure pulses to not only extract more mass flow through the engine (increased delivery ratio) but to produce a high pressure ďpluggingĒ pulse at the exhaust port just prior to port closing (increasing trapping efficiency). It works like a supercharger with no moving parts.

As far as engine life is concerned, itís difficult to get the same useful life out of a two-stroke when compared to a well-designed four-stroke. The two-stroke engine is inherently a thermally limited machine (due to the double power stroke frequency) and is most always equipped with rolling element bearings (out of necessity) which have a lower life span than plain, oil lubricated journal bearings. This, combined with the somewhat marginal lubrication method when compared to a four-stroke, usually translates into fewer running hours between overhauls for the two-stroke.

There is a way to make the two-stroke match the exhaust emissions and fuel economy of a four-stroke and that is to employ a direct-cylinder fuel injection system. The Mercury Marine Optimax outboard is a two-stroke, V-6 engine using fuel injection directly into the combustion chamber. The engine scavenges with air only, thus any scavenge air lost to exhaust contributes nothing to emissions. By injecting fuel into the cylinder near the end of the scavenge process means virtually 100% of the fuel is trapped for use in the combustion process, instead of being wasted out the exhaust. These engines have all the benefits of a carbureted two-stroke (light weight, small package volume, high power density) with the same fuel economy and low exhaust emissions of the four-stroke. The down side is the fuel system is expensive, electronically controlled, and quite costly...something not suitable for a small utility engine. To hear one of these run is quite interesting...totally misfire free and perfectly steady at idle and part load. At higher loads and speeds it sounds just like a V-12 four-stroke! Lubrication is by oil injected into the inlet air system via a metering pump. With the crankcases pumping air only, only about 2/3 of the oil is necessary for lubrication of pistons and bearings when compared to a carbureted counterpart. This is due to no gasoline mixture in the induction air which tends to wash oil off of the critical components. With this reduced lubrication requirement, visible exhaust smoke is totally eliminated.

To address the original question of why there arenít more vintage two-stroke utility engines around these days, is probably the four-stroke was always the preferred choice for reasons already mentioned in the other posts, and thus manufacturers concentrated more on producing four-strokes to fill the demand. Mixing fuel and oil is something that most consumers like to avoid. The majority would rather run their four-stroke lawn mowers, never change the oil, and just buy a new one in 2 Ė 4 years. The Jacobsen Company was an exception though...they produced high quality two-strokes that were used on commercial equipment, such as greens mowers, etc. These engines had a very good reputation for reliability and dependability.

Two-strokes have always been my favorite form of internal combustion engine. They are simple mechanically, but quite complex in the gas dynamic processes which need to be harnessed properly to attain improved performance and efficiency. In order to meet emissions standards, a high-tech fuel injection system must be used. This adds interesting challenges to the engineering and design process. I hate to see this engineís demise, driven by the ever-tightening exhaust emissions regulations. A simple, mechanically based, direct cylinder fuel injection system (costing no more than an equivalent carburetor) could keep the utility two-stroke alive and competitive. This is a project that I independently continue to work on and experiment with. No breakthroughs yet, but I have high hopes.

Dave Kirk
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Old 06-05-2008, 12:14:43 PM
Jim Metzger Jim Metzger is offline
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Default Re: Why are two strokes so uncommon

Hi Dave,
Your response was very well thought out and put. The snowmobile industry today is one of the best battle grounds determining whether 2-cycle or 4-cycle engines will prevail for snowmobiles at least. Yamaha adopted 4-cycle technology some years ago and offer an excellent line up of sleds getting decent mileage, but come with a weight penalty. Ski-Doo seems to be busy in the laboratory developing modern 2-cycles, that through direct injection and other state of the art techniques, offer superior horsepower per cubic inch in a much lighter easy to package engine offering even better gas mileage than the competitors 4 strokes. The arguement can still be made that no matter how clean 2 stroke exhaust gets they still pose a 100 loss of the lubricating oil from the oil injection system. Polaris and Artic Cat offer both types in various sleds but do not, at this time, seem to want to be the leader. Venues like Yellowstone Park and others only allow 4 stroke sleds and in very limited numbers to ride in the park. The string trimmer industry has dabbled with both types as well. I am not sure, but it seems I remember reading that the state of California has a phase out date for all and any types of 2 stoke powered anything. I wonder what the chain saw industry is doing for their part in 4 strokes?
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Old 06-07-2008, 01:48:50 AM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Why are two strokes so uncommon

The phase out is already going on in California, they are always ahead of the rest of the USofA. The phase out is going to be federally mandated.

As for lawn boy mowers - there are always exceptions. I worked in a shop, and have been working on small engines over 48 years, so I have 'some' experiance. Most of the lawn boys either had deck fractures (casting fault-fatigue from vibration), or bearing failure. Most had such loose bearings, that the magnets in the flywheel would rub the magneto core! With most of these machines, poor maintainance was probably more of an issue, than poor design, As with anything else, care makes for a longer lasting machine. As posted by others, if you do the proper maintainance, and keep the machine clean, it will last a lot longer than one you just put gas in and go!

A friend had a Saab, a B-10 I think, and it had a 3 cylinder engine in it. You could always hear it coming down the hill near the end of my street, and you could tell when Tommy hit the gas: ding ding ding ding BOOM (afterfire out the exhaust) then WAHHHH winding up speed!. That weird looking car could accelerate though!

Even with direct injection, there is still oil being burned. That is the biggest problem with the oil burners. I read once in a power mechanics magazine, that a chap had designed a 2 strole engine, with a ceramic block, It had sealed bearings, and minimal oiling needs for the rings. As the block was ceramic, no real cooling system was designed, as the engine ran hotter, it was more thermally effecient. We had discussed the engine in a mechanic shop in highschool, and were waiting for further progress on it. After a year or so, it dropped from the magazine's interest.

I had a Suzuki T 500-R 2 stroke motorcycle. It was a twin cylinder. The stock T 500 Titan had 42 HP. My T500-R had 78HP, out of the box - before modifications. The bike weighed 245 pounds with a full tank of gas. Talk about a road rocket!!! The biggest problem with that bike was keeping the front wheel on the ground! Talk about a power to weight ratio! The Puch 250 Twingle was a sears bike. Fully enclosed everything - wheels, chain, frame, body, everything! It was built in 1971, and looked like it was from the '50s! It weighed about 425 pounds, had about 14 HP, and had a top speed of about 70 MPH. Down hill. Up hill though - you could not stop it. It had tons of torque. I have had 4 of these brutes over the years, 3 250s and 1 175. 2 of the 250s were sears jobs, as well as was the 175. The other 250 was Puch thru and thru! the sears units were made in Czechslovakia, and the Puch was Austrian! I learned to ride a motorcycle on the 175. 16:1 gas to 50 weight oil, and shake well even before you start it! Smoke like a fool, until it warmed up, then don't follow too close behind, up hills! That machine would only go about 60 MPH, but it would out climb anything else in the woods!

As for 2 cycle engine exhaust - The exhaust port on a 2 stroke is typically the hottest part of the engine. most 2 stroke engines have some kind of muffler for several reasons. 1st is the noise issue. 2 strokers are inherently noisy, due to the fact that the exhaust port is opened suddenly, and the exhaust gas volume blows itself out of the cylinder at a prodigeous rate. A muffler does what it says - it muffles the sound. 2nd, is the issue of the amount of heat being released. Running a 2 stroke with no back pressure on the exhaust can lead to piston or cylinder failure, especially on engines running at high speed, with aluminum pistons. With a muffler, the exhaust gas flow is cut somewhat, stopping the blow torch effect. Also, it prevents fresh air from entering the exhaust ports, and causing a lean out condition. I used to love taking the baffles out of my Sears/puch machine's dual exhaust system. it sounded neat, and you could hear it for miles-literally. The only drawback - every time I did it, I ended up melting out the front piston of the machine, which was the exhaust piston port end of the engine. Granted, $7.20 for a piston and $2,00 each for the 3 rings wasn't much, but the 3 week wait for new parts was a killer! (I finally got smart and bought 3 pistons and ring sets!). I never did run the 250s open exhaust! As for the maytags, due to the nature of the 92, 82, and the uprights hit and miss action, you probably won't hurt them much, due to them being all cast iron piston and cylinder. They probably will run better with the exhaust pipe and muffler attached, but it seems that people like to hear the pop of the exhaust pulse and the purr of the engine coasting on compression. As the engine is turning with no ignition, fuel/oil mix is lubricating the piston and cylinder between firings, That is why the hit ans miss maytags leave such a mess, the raw fuel and oul just goes out the exhaust. On the twins though, it is another story. That engine fires constantly, having a throttle governor. Run the twin without a muffler, and it is liable to run unevenly, and keeping the mixture even will become the day's event! Run the twin under a heavy load, no exhaust muffler, is liable to buy you a pair of pistons before long! The twin needs the back pressure under load, for reasons explained above. The faster an engine runs, the more important the muffler becomes. Running a 2 stroke open ported, is an invitation for melt down. Modern 2 stroke engines actuallu have a 'tuned' exhaust. The shape and length of ther exhaust system is calculated to give the best power and effeciency. Tuning an exhaust is not a modern phenomenon, though. A 1902 Detroit Engine Works 2 cycle marine engine I had, had a tuned exhaust system. It had a muffler, with a special provision: When the exhaust port opened, the exhaust gasses went right into the exhaust chamber of the muffler. Within a split second, the gas flow was slowed due to the chamber's shape. you would think that slowing the gas would not allow the engine to scavenge properly, but Detroit had an answer to that problem. Their answer was to inject water into the exhaust pulse at the precise time it entered the exhaust chamber. The result was that the exhaust pulse was rapidly cooled, to the point that it actually pulled a slight vacuum on the now empty cylinder, making for a more effecient fuel/air transfer to occur. An ingenious solution, don't you think?

Andrew
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