advantages and disadvantages of 2 and 4 stroke engines

[tenlizard]

what are the advantages and disadvantages of 2 and 4 stroke engines?

 

[Russ2251]

I plead no contest...
My opinions on 2 cycles are HIGHLY biased and I just can't be fair and balanced to my Otto cycled friends.
I stay as far away as I can from 4 cycles.

 

[Kenny_McCormic]

2 stroke makes roughly double the power of the 4 with less parts and weight, most have bad emissions and you have to mix your fuel and do it right or the motor wont last through a gallon of gas.

4 stroke generally burns cleaner than a 2, burns straight gas and makes roughly half the power of a 2 stroke of similar displacement.

I currently run a 4 stroke but there is more than one 2 stroke BEGGING to be installed, just dont have the money and its getting cold outside.

 

[fluxcored]

I have always wondered: Is there any way to distinguish between a 2 strioke and a 4 stroke at a glance?

If I find an oil filler cap, I always assume it to be 4 stroke but that may not be true in 100% of the cases?

 

[modelengineer]

I usually look for the "2stroke" or "4stroke" label on the engine

But seriously, I think there have been a few wet sump 2-strokes but not very successful, otherwise we would see more of them. Looking for the oil filler cap is probably the best way. That, or looking at where the carb comes from. If it comes from near the top of the head then probably a 4 stroke. If it comes from the rear or front of the crankcase, or the bottom/middle of the cylinder then chances are its a 2-stroke.

 

[fluxcored]

Good one, Andrew - can't for the life of me figure out why I've missed that label.

 

[Magice]

An expansion chamber if there is one means it's a 2 stroke.

 

[kibble]

If you see the carb attached directly to one side of the engines cylinder and the exhaust attached on the opposite side of the cylinder, usually a two cycle. 2 Cycle crankcase's tend to be smaller as well as they don't have all the parts needed by a 4 cycle motor.

 

[2or3wheels]

You idea with a dip stick can be misleading. Many 2 strokes have transmissions that have dipsticks, bit those with dipsticks usually have huge expanshion chambers on their pipes.

 

[Kenny_McCormic]

I usually look for the "2stroke" or "4stroke" label on the engine

But seriously, I think there have been a few wet sump 2-strokes but not very successful, otherwise we would see more of them. Looking for the oil filler cap is probably the best way. That, or looking at where the carb comes from. If it comes from near the top of the head then probably a 4 stroke. If it comes from the rear or front of the crankcase, or the bottom/middle of the cylinder then chances are its a 2-stroke.

From what I have heard all new 2 stroke outboards run a direct injection system with a wet sump.

 

[Jerryburger]

I think if more 2 strokes of the easy-to-mount / easy-to-hook a PTO up to were built, they'd dominate this forum with a few high dollar 4-stroke challengers thrown in here and there....

...BUT... "easy-to-mount / easy-to-hook a PTO up to" describes a common utility motor, which must jump through several Lowest Common Denominator requirements... that's one of the reasons why the B/S flatty was/is so prolific. They were designed to be easy to generically mount, turn a shaft at a regulated 3600 rpm cheaply and reliably- that's it.

Russ has demonstrated that even a 2-stroke "utility motor" (LawnBoys) are pretty quick right out of the box. (My Favorite is the "LawnBoy Classic 4.5hp".... It was my "AHA!" moment.)
Can you imagine the $$$ invested in Jr. Tyler's dragster engine being used to develop a LawnBoy motor into a LawnMAN engine? (SuperBoy?!?...Tarmac-ShredderBoy?..). Scary!

I think if a person can figure out how to mount and run a PTO from a 2-stroke for their project, they should do it.