10/19 – OEM 372xpw and Hairun/Farmertec 52mm Piston & Cylinder + General Aftermarket considerations

[Spring1898]

Got a few more aftermarket P&C’s to do some more comparison.
As always remember these are samples of 1.


In this, we compare New 52mm Hairun Nikasil and Farmertec Chrome plated cylinders to a NOS OEM 372xpw 51.4mm cylinder. (Note: they are in fact 52mm, so the pistons will not fit an OEM cylinder)


For those who don’t know, Hairun is the company in mainland China who manufactures the Huztl/Farmertec brand P&C’s as well as probably most of the “unbranded” ones sold around by Ebay.

Farmertec P&C’s to my knowledge only utilize Chrome plating, whereas the “unbranded” ones can be found with ceramic (nikasil) plating.

(Hyway is a separate Taiwanese company who has its own factory in Taiwan. They also sell aftermarket parts, including P&C’s, which are considered to be of higher quality than those from China, albeit more expensive)


Cost of Farmertec/Hairun = $25-$30

Cost of OEM = $150



External Appearance – Order is OEM, Hairun, Farmertec

OEM wins, no surprise. What is nice is that the castings of the Hairun/Farmertec cylinders have improved noticeably compared to years ago. Arguably external appearance is not a real factor in performance, but it does show incremental improvement within the company which is important.

Note the ground off logo on the Hairun. This may have originally been slated to be a Farmertec Cylinder.




Internal appearance

All Bores and Chambers appear uniform and about the same size.

Plating seems adequately uniform. Hairun is ceramic, Farmertec is chrome, OEM is ceramic

Unlike a Hyway cylinder, none have a plated chamber.

There are some plating “drips” left in both the Hairun and Farmertec Cylinders. But aside from being smoother, don’t appear to impose into the cylinder in any palpable/meaningful manner.

The cross-hatchings on the Hairun are the most pronounced and slightly palpable. OEM is next, but not palpable. Farmertec has the least visible and is the smoothest.



Weight

OEM = 1lb 4.9oz

H = 1lb 4.1oz

F= 1lb 5.5oz

 

[Spring1898]

Intake and Exhaust

Exhaust:

Externally they are all very similar, with effectively equal sized openings. The Hairun is almost identical to OEM. The Farmertec is slightly mishapen, but not so much I would be concerned.

Internally, OEM has much more uniform opening and slightly more rounded. The Hairun and Farmertec both suffer from a peak at the bottom of the port. Farmertec also has a somewhat jagged bottom edge. All have effectively the same sized opening.

The intakes are very similar between all three.

OEM channels are finished smoother than AM.

All openings are slightly off center it should be noted, OEM slightly less than the AM’s.

 

[Spring1898]

Transfers:

Beveling on the OEM internal port openings are very uniform. It is sufficient on the AM’s, but definitely not as clean.

The skirt coming off the cylinder in front of the transfers is cut much lower on the Hairun and Farmertec. Whether or not this does anything performance-wise is arguable

The OEM cylinder has a ramp or bevel on the exhaust side lower transfer to funnel air through the transfer (note this is not present on the original 372xp cylinder), but effectively decreases the overall size of the transfer.

Neither the Hairun or the Farmertec have this step which effectively enlarges the transfer, and both the Hairun and Farmertec have a thinner divider between the 2 ports, effectively leading to a significantly larger port size. The sizes are slightly larger but similar shape to the OEM 372xp 50mm cylinder.

The exhaust side transfer opening into the cylinder is effectively the same size as OEM.

The intake side opening is notably smaller, due to the smaller flange opening into the cylinder. Any gains from this factory “porting” may be lost.

The interior surfaces on the OEM cylinder have many small jagged protrusions. Interestingly the AM’s are in general smoother than OEM, but have a few larger bits of slag.

 

[Spring1898]

Pistons:

I have 4 to compare

L->R: Hairun – Hyway “Pop-Up” – OEM – Farmertec

Hairun – Single ring, thinner bottom of the skirt, Oil retaining lines, sharper edges

Farmertec – Double ring (like OEM xpw), different casting shape compared to Hairun. Thicker skirt edge, more polished and smoother than Hairun.

OEM – Finer oil retaining rings, not polished. Least sharp edges

Hyway 52mm Pop up – Will not fit OEM! Not quite as smooth as OEM but close, very fine oil lines. Very thick skirt.

The Pop-up begins about .375” from the edge and about 0.020” height above the deck. These measurements seem uniform across Hyway’s pop-up line. I have seen some reviews claiming around 10psi increase in compression. A video of an Aussie 660 on youtube showed around 18psi. I have not had the chance to check a well broken in OEM with a well broken in Hyway on the same cylinder/application.

All weigh ~3oz give or take 0.2oz

 

[Spring1898]

Opinions:

These are 52mm copies of the original 50mm 372xp cylinder, not copies of the XPW. A better comparison may be to the OEM XP cylinder. A consideration for the future.

I also find it interesting that the OEM XPW cylinder has notably smaller transfer volume than the original XP cylinder.



Nitpicking vs practical significance and realistic expectations:

OEM Superiority: Of course, for the price and engineering it should be. One should not expect OEM performance for 20% of the cost.

But ALL the smaller defects noted in this comparison I have also found in OEM cylinders. Quality control of OEM is better, but you can still find jagged edges around ports, offset openings, etc

Port timing and degrees: I would guess that there is a difference of significance. To determine that would take too much time.

Performance: I don’t think these could compare to OEM XPW. I suspect they are inferior but closer to OEM XP and above OEM 48mm 365’s.
From what I have seen, between the inferior port and transfer designs you lose top end. With displacement and compression from a base gasket delete you can gain torque.
I agree with a certain Farmer that compression can make up for a bit.

The “10 Minute Rule”
I find a cylinder acceptable when there are only small defects that can be rectified in 10 minutes or less either by hand or with a simple rotary tool


If you choose to buy one for an application, I would suggest buying from a large volume seller. They are more likely to have recently made cylinders with the latest improvements from the manufacturer. A low volume seller may have inventory months old.




Preview: I have a Hyway 272xp pop-up kit and initial impressions are very good. Comparison to follow once I pull of the OEM 272 jug to compare.

 

[roy wilson]

good info there have not heard of that Hairun one tho do yu know where they are ? , i often get the farmertec kits but do tweek them a bit with flashing or minor port defects but have been fine so far and use caber rings as they seem to be better as the black farmertec ones seem to be failures sometims , not that i have , but choose better rings

 

[Axotopia]

Spring1898, thanks for taking the time to post the photos. Great resource for the rest of us to be able to see the difference side by side.

 

[morbius18]

I have a farmertec 372xp big bore kit. The saw I was going to install on to test is a 365sp. I measured squish on it .047" without a gasket. I don't have a lathe to modify it, so immediately it was ruled out. I ended up cleaning up and porting the OEM 48mm 365sp cylinder. Squish was .024 without gasket.

To summarize, the ports could be beautiful, plating beautiful, but if the squish with a gasket is roughly .060", compression will be horrible. You should check this with your cylinders also.

 

[Spring1898]

That should have been a reason to return it. The worst one I have encountered was low 40's. Best, in terms of squish was 0.25"
I pretty much do gasket deletes on all I do.

Quality consistency is lacking. They know this and generally are accommodating. They are constantly in a state of "improvement" and changes which probably helps and hurts consistency. We the end users are basically the 3rd phase clinical trial for these. So definitely let them know your feedback.

 

[morbius18]

I get the canned response from huztl when dealing with them. Something like, 'It look ok according to our tech, try run it and see'. I just know if the base is that far off, I wonder how off the port timing is as well. I don't think it's worth my time to clean up, port and then deal with such a high squish. I agree, it should be returned, however huztl disagrees, it run ok, try it.

 

[RBurtcher]

Thanks for your effort.
The lower left combustion chamber looks very poor. Sharp edges and not very uniform. OEM looks good.

The price of the OEM P&C for this saw seems like a bargain.

 

[Spring1898]

Lighting was not the best in these pictures, also trying to get the camera to focus on all three simultaneously was a bit of a challenge

From what I recall there were no major defects in any of the combustion chambers, they were all round and uniform. What it looks like in the picture is created by the shadow from the light and a line of machining dust which I did not clean off before the pictures. Not saying that there are not cylinders that make it through with such defects, but that was not the case here, nor have I seen any personally.

I spend 2-3 hours with the cylinders during this process. Pictures are for everyone else's benefit but they are definitely limited.

 

[morbius18]

I get the canned response from huztl when dealing with them. Something like, 'It look ok according to our tech, try run it and see'. I just know if the base is that far off, I wonder how off the port timing is as well. I don't think it's worth my time to clean up, port and then deal with such a high squish. I agree, it should be returned, however huztl disagrees, it run ok, try it.

I purchased an OEM 372xp cylinder, and in preparation, I removed the ported 365 special cylinder. I put the huztl farmertec big bore 52mm on the saw and degreed it.

Exhaust was 102
Intake 82
Transfers 125

This was without gasket

 

[Rennsman]

It’s been a while, has anyone compared the hyway BB kit to these?