10/19 – Comparison “OE” OEM 272XP and Hyway “NE” 52mm Cylinder w/ Pop-up Piston

[Spring1898]

I have been looking forward to this comparison. I picked up a very used, but very clean 272XP from an acquaintance. It belonged to his Father who bought it new and used it heavily on several hundred acres. Well maintained, and never rebuilt. It looks externally a lot younger than it is.

No scoring on the cylinder, but plating is getting noticeably thin (though mostly uniformly) on the intake and exhaust sides of the cylinder. This is how a cylinder should die; from old age and use, not a catastrophic failure. Could get more out of it, but figured a good opportunity to see what is available in the aftermarket.


The first thing you will notice is that they are 2 different cylinder styles. OEM is the original Mahle version of the cylinder. Hyway looks like it copied the newer style still used in new 272’s manufactured in Brazil (and what you will get if you purchase new OEM). So not entirely an apples to apples comparison, and as I don’t have one of the new 272 style cylinders, I can’t tell if the differences are due to changes Hyway made or just differences between the “OE” and “NE” 272’s (note the new 272’s have a slightly lower rated output)


Cost of Hyway Pop-up kit = $72

Cost of “NE” OEM = $140


External Appearance – OEM on the left, Hyway on the right

The first thing you will notice is that they are 2 different cylinder styles easily identifiable by the 6 vs 7 fin set up of the OE vs NE respectively. Casting is cleaner on the OEM no surprise there.

Hyway always seems to have extra thick fins on all their castings. Not sure if this is by design.


Using the bottom of the base as a reference we can see that the Hyway cylinder drops into the case about an additional 0.035” give or take a few thousandths. This will come into play later, where we will reference the bottom of the cylinder and bottom of the base for measurements.




Internal Appearance

All bores and chambers appear uniform and effectively the same size. The chamber on the Hyway is plated.

Plating is uniform on the Hyway and much nicer than on Chinese cylinders.

Crosshatchings are uniformly distributed on the Hyway, but not as pronounced as those still remaining on the “low wear” areas of OEM.

 

[Spring1898]

Intake and Exhaust

Exhaust:

Externally very similar, no differences worth noting.

Internally, the OEM beveling is very subtle and there remain some rough jagged edges along the perimeter.

The Hyway has no such jagged edges and has more pronounced beveling, but is not as perfectly ovoid and has a wavy appearance.

The ports themselves are smoother on OEM than Hyway.




Intake:

Externally the Hyway matches OEM fairly well, but here is my first point of concern. Note the impulse port “counter sunk” area and its proximity to the intake. It is drilled too close to the intake, leaving only a narrow span for the gasket to rest on.

Internally the ridge formed to house the left carburetor bolt is fully cut back on OEM. The Hyway left part of the ridge which leads to an “indentation” on the internal opening. Probably does not affect anything in practical terms, but I think it is worth mentioning. That entire side of the port looks a little less machined than the rest, so it may have been an oversight during manufacture.



So remember what I said about base vs cylinder reference?
If we use the bottom of the base as a reference, the openings of the intake and exhaust are in the same position on both OEM and Hyway. (which is then, by extension, 0.035” higher relative to the bottom of the cylinder)

 

[Spring1898]

Transfers

The lower transfers on both Hyway and OEM are very uniform and square, with appropriate beveling. OEM again uses slightly less pronounced beveling compared to other cylinders. The rough edges around the port make a return, forming a noticeable ridge before entering the transfer port. These ridges are not present on the Hyway.

The upper transfers on the Hyway are less square and less uniform than OEM, particularly on the intake side where they are much more rounded.

The interior finishing of the ports reveals smaller but more jagged protrusions in OEM. The Hyway has relatively larger slag, but more rounded, leading to a much smoother feel.

The biggest difference is that the Hyway ports are cut both deeper and wider than OEM. Again, not sure if that is Hyway’s decision or the difference between OE and NE versions of the 272 cylinders.


The position of the ports on the Hyway is slightly different than OEM. Relative to the Bottom of the Cylinder they are in about the same position, which makes them around 0.035” lower than OEM relative to the Base)

The rest of the measurements are roughly the same so they have simply been shifted in the Hyway. Again, not sure if that is Hyway’s decision or the difference between OE and NE versions of the 272 cylinders.




Weight

OE OEM = 1lb 4.0oz

NE Hyway = 1lb 5.8oz



Pistons:

Casting of the Hyway is slightly thicker all around, skirt thickness, piston boss, etc.

If you look closely you will notice the hole in the boss is cut slightly higher on the Hyway. This looks done intentionally, as it maintains the same height to the top of the piston. Putting a wrist pin between both OEM and Hyway demonstrates this. The offset does not concern me as the additional material around the boss is still thicker than OEM. (Note: OEM is not entirely centered either)

You may also notice the head of the piston extends down lower on the Hyway than OEM. This also appears intentional as, you may have guessed, it is about 0.035” lower than OEM.

The Pop-up begins about .375” from the edge and about 0.020” height above the deck.



Weights (with rings):

OEM = 2.8oz or 80g

Hyway = 3.0 oz or 86g




Opinions:

Overall I am impressed with the quality of the Hyway cylinder at 50% of the cost of OEM. My only real concern is the space around the impulse port as mentioned.

As to the difference the in the height of the transfers relative to the base, I will let those more well-versed in 2-stroke theory explain the potential effects.

The diameter is the same on both OEM and Hyway, meaning the Pop-up piston can be used in both. I am not sure what effect, if any, there would be on an OE OEM cylinder with its transfers slightly higher. Again, 2-stroke theorists could explain it better than I can, but I suspect in practical terms it doesn’t matter.

 

[Yotaismygame]

Thanks for taking the time to do this. I'm going to be buying one of these Hyway top ends for my 61 to 272 build here soon. Where did you find the Hyway with pop up kit so cheap? best price ive seen is $96

 

[Spring1898]

I get them directly from Hyway. Subjectively I have gotten nicer looking parts that way than from resellers, but that could just be a fluke.
It takes a little long for them to arrive depending on how much you order from them. I usually purchase multiple items at a time to spread out the shipping cost.