I doesn't matter. In the past they used to sell reverse rotation crankshafts for glow engines, that had one piece crankcases. Those engines ran just fine backwards with the exhaust on the same side.

+1 airraptor

Some on here are failing to note all the twins out there that use the same piston and cylinder on each side of the engine. One is effectively 180 degrees turned from the other with respect to rotation ...... and they run just fine that way. It is completely unnecessary to rotate the cylinder 180 if the rotation is reversed.

I'm sorry I guess you could turn them around but I would think the p
orting would be screwed up. Look at the cyl base gasket.
BC

Exact. But also compression is the same than. If you leave the cyl and piston and just position the ignition sensor to the opposite side you will have increased compression and need to richen the needles a lot and still end up with an engine that is just not running ok.

Sorry....Do you guys read? Have you even reversed an engine once? You all claim that is not nessecary to rotate the cyl and piston, you claim it can't be done. I just told you that i did on the dle55. Just rotate youre prop the other way on youre own engine by hand and you will feel the difference in compression. This difference can only be taken away by rotating the cyl and piston.
Rest my case. Pffff.

The reason the cylinder cannot be turned around without modification is because of the reliefs for the reed block and rear bearing are different on the bottom of the cylinder.

Well all i can say is: did you try? No, because youre answer is wrong. theres no need for further modification in the dle55.

The cylinder base gasket is squareish with four bolt holes and a big hole in the center and is symetrical left to right

You have a Happy Easter too

Ronald explain to me how the engine knows its running backwards?
If the piston goes up to compress the air & fuel mix , then is pushed down by the burning of that mix. How does the engine know its running backwards?

The only thing that will be slightly different to the engine will be the forces applied to the crank pin and piston rock as the piston is pushed up from the opp side of the engine.

Most purpose built gasoline 2-strokes dont have crankshaft induction. This is where running in reverse would cause problems. Airraptor is right - the piston moves in the same direction. Regardless of the induction path, they should operate in either direction providing the timing is adjusted accordingly. If using Glow ignition, nothing needs to be done other than to start the engine the other direction.

I dont see the point in reversing the cylinder/piston though.. Unless induction or exhaust routing were difficult, it shouldnt need to be changed the way I see it.

For those that think running a 2-stroke engine in reverse changes the compression ratio or how 'well' the engine runs, point me (or anyone else) to some literature that explains this phenomena. I'm intrigued as to how this works differently on a gas engine than it does on a glow engine.

I think the deal about the compression feeling different in the different directions has more to do with which side of the piston the ring gap is on and how the skirt of the piston rocks in the cylinder that helps seal off the compression when traveling in a certain direction.

I don't think the engine cares which direction it is running as long as the ignition timing is correct

Wow. <div>
<div>Making a 55cc engine turn clockwise. </div><div>
</div><div>  This is what these hobby is all about      <div>
</div><div>Good job guys </div></div></div><div>
</div><div>Please keep posting </div>

That makes perfect sense to me, and I agree.. The engine doesnt care which way its turning. None of my glow engines feel different turning them over CW vs. CCW. The pop past TDC sounds different but thats all.

About the only problem you'll have with trying to reverse the cylinder so that it can have the exhaust on the other side, is if the cylinder and crankcase are asymmetrical or not. Many of the gas engines nowadays have asymmetrical cylinders that won't let you do this as the ports are not cutout for it in the crankcase. You may or may not be able to cut the ports yourself as it depends on if the manufacturer left room in the crankcase for it or not.

As for reversing the piston, it really depends on if the piston is asymmetrical in design too. They sometimes have cutouts in the piston to clear things in the crankcases and to open up the ports more too.  The other thing is if the piston has floating rings or pinned rings. If the rings are floating it doesn't matter any, but if the rings are pinned then you have the align the ring gaps so it matches the cylinder sleeve to clear the ports.

But a two stroke engine does not care if it is running forwards or backwards. As long as you have the timing setup it is no big deal.

One thought is if the engine has been run and the rings are seated now, you need to try to keep the piston oriented to match the cylinder as much as possible so reversing the piston would be good then. I think if you are careful, you could probably reverse the cylinder and piston as a unit without disturbing the rings if you reverse it.

Now then many years ago I noticed with flat  twin cylinder two stroke engines that the left cylinder ran more rich and more cool than the right cylinder did. There is a uneven fuel distribution issue with the air fuel mixture flowing through the engine.  The air fuel mixture devlops a twirling flow pattern as it is drawn through the engine and the left cylinder is affected by it more. It is almost like the flow direction is un-natural in the left cylinder.  I was able to demonstrate it to some extent using a single cylinder engine where I reversed the cylinder but left the engine rotation the same. I did this with several engines not just a Fox 1.20 twin or a Fox .60, but also a MVVS twin and a MVVS 10cc engine too. Some guys running some other twins like the old Ross twins and quads also noticed it too. A geared twin like the Webra 1.20 did it too.

But if you reversed the engine rotation as well as reversed the cylinder so the exhaust is on the left, then you don't have the problem as the single cylinder engine now has its air fuel mixture flowing and twirling in the opposite direction, so it behaves the same then. But you can't do this with flat twin cylinder engines, as they have a common crankshaft of course. As if you reverse the rotation on a twin then the right cylinder starts to run more rich and cool and the left cylinder runs more lean and hot.

A lot of 2-strokes have a off-set piston pin, so you mite have to rotate the piston and cylinder if you what the off-set to do what it was design for.

True statement about the offset pins but very rare in most of the engines we use. None of the engines discussed in this thread have offset pins, at least the ones I that I have measured and inspected. This is mostly done in automotive and other special use engines to reduce piston slap / knock when the engine is cold. Now some engines offset the whole cylinder in the case to gain a bit of power but again this is rare in our engines.

Wow, this whole thread is painful to read. earlwb has some good points that I would like to add to. On the one example of an engine that was reversed here, there was reference to greater compression when the engine was rotated in one direction compared to the other. My bet is this engine had some time on it and had established wear patterns. On most any engine that is run in, turning the crank backwards will give you a greater feel of compression than when the engine is turned in the normal direction. This is due to rod angle pushing on the piston and the slight amount of piston rock in the bore more closely approximating real life run conditions than when turning in the normal direction. If one starts with a new piston and sleeve before the reverse process, I firmly believe that reversed engine will have a greater compression feel when turned in the normal CCW direction. Its all about wear patterns and the slight piston rock in the bore when the engine is hand cranked. Has nothing to do with which direction the cylinder and piston are installed. You simply get a better compression feel when the engine is rotated backwards to normal rotation. Don't believe it .... you can test this on most any ringed engine, large or small.

Now to open a new can of worms, if you can rotate the cylinder / piston in a DLE55, the piston skirt will wear less on the bypass side!

Tee hee Truckracer. You're right, nobody has mentioned rotation thrust wear yet....

AV8TOR

As Paul Harvey use to say, "and now for the rest of the story"!

On the DLE 55, all ones I've seen, had the port inlets and outlets internal to the cylinder and are the closed type and use a windowed piston to facilitate the air-fuel transfer. There are no ports at the bottom of the cylinder-crankcase mating area to consider. The cylinder gasket is the same, right side up or wrong side down. It is symmetrical left to right.

But the cylinder is relieved differently front and back for the rear bearing and the reed plate.

Also like several people have mentioned, there is no real mechanical reason to turn the cylinder around 180 degrees.  And there is no pin offset.

The DLE55 cylinder that has been available for several years now (since they recast it) have open ports that extend all the way to the bottom of the casting though they do taper in a bit at the bottom. Even the boost port opposite the exhaust port is now open ported and the casting bridge once present at the bottom of the cylinder is now gone. As you state, there are no mating machined ports in the crankcase but I don't have an engine apart right now to view to help describe them further.

Thanks for the info on the changes to the ports. I would like to see some pictures of the newer castings.

Where I fly everyone changed to the DA 60's and 120's when they came out and anything new DLE is more or less a thing of the past around here.

So I haven't seen any of the newer 55 cylinders

Tower doesn't update their pictures.

You're right, Tower still shows the older cylinder.

You're right, Tower still shows the older cylinder.