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Do two strokes inherently have to have oil in the gas?

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M61A!

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The short answer is .... no they dont need to have oil in their gas, if you use an oil injector, but the best way to make sure that the oil is in your fuel is to put it there yourself.
 

Dana

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Oil injections just eliminates gas/oil premix... the engine is still burning fuel/oil/air like any other 2-stroke, which I think was the original point.

-Dana

Always keep clothes and weapons where you can find them in the dark.
 

Dan Thomas

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Oil injections just eliminates gas/oil premix... the engine is still burning fuel/oil/air like any other 2-stroke, which I think was the original point.
Not all burn their oil. The older GM 2-stroke diesels and the huge ship 2-stroke diesels don't run the mix through the crankcase and use straight fuels. They have normal pressure-lube systems like four-strokes. They use superchargers to get the induction air into the cylinders.

But none of those will you find in an airplane. Just a bit too heavy.

Dan
 

Not Yet

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The new snowmobile 2 stroke engines are using various forms of direct injection. The fuel is injected in to the cylinder after the exhaust ports are closed or into the transfer ports late enough that none goes out the exhaust port. These engines are as fuel efficient and clean burning as the 4 stroke engines. They meet all the clean air standards, and 2 strokes have naturally lower nitrous oxides then 4 stork engines
They like most newer 2 stroke engines use oil injection. But these engines will not work on premix because there is no fuel in the crankcase.
 
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akwrencher

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Interesting thread/discussion. Anyone care to pick it up again? I have wondered off an on over the years if a two stroke could be modified like the original poster was asking about, mostly just for the fun of seeing if it could be done....

I have owned a Detroit diesel, and worked on quite a few others. No one here has mentioned that they have a VALVE train. Yes, they only have exhauste valves, but still need a cam shaft.

Hmm, what about using a small lightweight 4 and supercharging it, using the exhaust valves and adding intake ports, to get higher power/wight ratio? Might work with fuel injection, di or idi.....
 

cheapracer

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Interesting thread/discussion. Anyone care to pick it up again? I have wondered off an on over the years if a two stroke could be modified like the original poster was asking about, mostly just for the fun of seeing if it could be done....
.
Old thread but as I'm new I'm catching up ...

STEPPED PISTON ENGINE OPERATING PRINCIPLE

I have another on my computer as well that I will show you in a few days time when I remember to do it.

Lots of nonsense about 2 strokes within this thread also, I'll give this one 5 minutes ..

Sir, with all due respect, you are incorrect. It is well known that at a given RPM 4 strokes generally have more torque.
This is the single biggest fantasy that there ever has been in the world of engines, second only to 2 strokes rev more than 4 strokes.

Taking motocross as an example, 450cc 4 stroke are needed to compete directly with 250cc 2 strokes and 250cc 4 strokes are needed to compete with 125cc 2 strokes.

TWO-STROKE VERSUS FOUR-STROKE: 2012 KTM 250SXF VS 2012 KTM 250SX | News | Motocross Action Magazine

In Grand Prix racing, 600cc 4 strokes have just directly replaced the 250cc 2 stroke class and in the last years of 500cc 2 strokes Grand Prix bikes, 1000cc 4 strokes were required to be competitive against them eventually replacing them.

Unfortunately one of the things you forgot to mention about 2 strokes is that their plugs foul readily unless cleaned religiously.
Try setting your carby and oiling up correctly and you'll never touch your plug again. It probably fouls because you did touch your carby and oiling.


2's are mechanically simpler but their higher RPM's are going to be more prone to failure simply because of high rpms. Look at a freight train, their wide open throttle is something like a few hundred RPM. And they will go half a million miles and they are mechanically very complex with lots of moving parts.
4 strokes need to rev way higher than a comparable 2 stroke and many freight trains are 2 stroke.


What do you feel about 2 strokes automatically wearing out faster than 4's based on RPM? I don't necessarily agree with that. It depends more on HOW you run an engine than HOW FAST.
RPM has nothing to do with it, 2 stroke rings have ports to transverse, simply having less surface area to ride on and running over the ports edges causes faster wear but in balance 2 strokes are twice as fast to replace the rings, status quo. Also most 2 strokes sold are competition machines with thin rings than non-competition engines. 2 of 2 stroke bikes I have owned bought brand new, being a Suzuki TS250X trail bike and a Yamaha RZ350, both came with full warranty and neither were touched internally for around the 3 years I owned them riding daily to work and weekend rides, about 15,000kms each. Never touched the spark plugs in either by the way.

There are big movements to get back to 2 stroke dirt bikes recently, such is the cost of owning a competition 4 stroke along with the huge maintenance required.

Husqvarna Two-Stroke Dual-Sport Concept Bike- Two-stroke Resurrection


I love chats like this. We learn so much! :)
You obviously need to have more chats.
 
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M

Manticore

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Limbach Flugmotoren GmbH & Co. KG from Germany (EU) have been successfully building aircraft engines for over 30 years.

This is what Peter Limbach says about their 2-strokes:

"What conditions does the engine life depend on?
Two stroke engines in general do not like continuous operation. In this mode of
operation the piston ring grooves tend to fill up with carbon deposits and at a time the
piston ring might stick. A sticking piston ring will definitely lead to engine failure. The L
275 / L 550 series engines feature a tapered piston ring to prevent sticking rings but
depending on temperatures, type of fuel and oil, the possibility of ring sticking cannot be
excluded. Limbach Flugmotoren recommends to remove pistons and cylinders and to
decarbonizes the pistons, rings and cylinders every 75h.
Another limiting factor are vibrations, which can lead to worn carburetor linkages,
premature coupling failures etc."
 
N

Niels Abildgaard

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I drove 80000km at 80% power on my single cylinder MZ 250 on one sparkplug and never decarbonized.
Se Subaru thread for picture
Reason for giving it away was my age.
Engine ran as well on final trip as on first.
 

cheapracer

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I drove 80000km at 80% power on my single cylinder MZ 250 on one sparkplug and never decarbonized.
.
Niels, a guy who I used to work next door to had Australia's largest collection of MZ's including a late model like yours. If you ever need to contact him PM me.

I am a CZ man myself having raced many a 250 and 400 and my best mate has a few side pipes and a 360 twin port.


This is what Peter Limbach says about their 2-strokes:

Limbach Flugmotoren recommends to remove pistons and cylinders and to
decarbonizes the pistons, rings and cylinders every 75h.
Well with that antiquated design what do you expect, maybe they should release a new model rather than stay with a 30 year old design, the cooling finning is awful, 1960's awful.

Not that 75 hours is a hugely bad thing for 2 hours of maintenance and a couple of new rings/gaskets, it's something I do once a year with my race bikes for the new season anyway needed or not.

I would be interested in doing a small 2 stroke engine myself but with aviation coming to China in a big way I believe the market in 5 years will be flooded with small engines and ultralights so not a good business move me thinks.
 
M

Manticore

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I drove 80000km at 80% power on my single cylinder MZ 250 on one sparkplug and never decarbonized.
Se Subaru thread for picture
Reason for giving it away was my age.
Engine ran as well on final trip as on first.
I didn't know there was enough power in those things to pull a fuel tanker.;^}
Incidentally, how did you manage to stay awake for that length of time?
 

Aviator168

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with aviation coming to China in a big way I believe the market in 5 years will be flooded with small engines and ultralights so not a good business move me thinks.
Yeah. Cheap engines are all you are going sell to fly in the air space bellow 1k meters they just opened up. I see lots of detonations coming. The thing is, even a good two stroke is not cheap.
 

cheapracer

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The thing is, even a good two stroke is not cheap.
Yes they are actually, that's the whole point of a 2 stroke.

The reality is it's all about demographics, you guys are willing to pay through the nose for anything "Aviation", it's a scam that I have laffed at for many years in motor racing, go buy exactly the same part at a circuit racing, rallying, speedway and off road shop and you will get 4 wildly different levels of price accordingly, respective to that order.
 
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