Wonderboy's Metro XFi Revival

[Wonderboy]

I finally got back around to working on rebuilding this engine. I went out and bought a flex-hone to deglaze the cylinder walls, as seen in Johnny Mullet's great G10 rebuild guide. Today I deglazed my cylinder walls using the flex hone (or berry/dingleberry hone). I used some 5W synthetic oil as the lubricant instead of hone oil. It seemed to work alright. This is what it looked like when I was done honing:

Then I used some carb cleaner (couldn't fond any WD40 lying around..hate it when that happens) to clean out the cylinders of the residual oil and grit. The Mullet advised on using something to protect the crankshaft journals from getting grit on them, so I initially wrapped each of them with an old sock from below. This didn't work out well, as the hone got a hold of the sock, and ripped one of the berries off, and twisting two others towards the center of the bit. I ended up not using anything to protect the crank, which worked out alright since the oil I used stayed viscous enough to not get everywhere, and was easy to clean up.
This is what it looked like after cleaning. Notice the little discoloration toward the bottom of the middle cylinder...is that okay? Should I try to use the hone for longer? It feels no different to touch than any other part of the cylinder wall.

This is a closer look at one of the cylinders after cleaning.

The main question here is with the new rings. This came as a bit of a surprise to me, as I got my replacement rings from partsdinosaur, who sells a special XFi ring replacement set. However, the compression rings that came with it do not have the nice angled overlap that the original rings have:

All of the original rings still seem to be in good shape, all have the same amount of gap and spring force. The only difference between them is that the new ones are a bit stronger when compressed, rendering them almost difficult to push down into a cylinder, versus the old one which goes in a little easier, but not easy like throwing a hotdog down a hallway if you catch my drift.

Here is what the new ring looks like seated in a cylinder:

Old ring:


Is my inclination to continue using the old compression rings and only replacing the oil rings well founded? Let me know what y'all think.

Will

[Christ]

Will,

If the new rings create a total seal with no obvious gap, then they're fine to use. With a single compression ring, the fear is that there will be obvious blowby from combustion, putting mixing combustion gasses and oil.

As far as that area in the cylinder, if the piston rings don't touch that spot at full travel, probably not really a big deal (unless you're anal about cleanliness).

Technically, the skirt will rub against it, but as long as you oil the piston skirt before you put it in there, it should be OK and will polish that spot.

Your cross hatch looks pretty good for apparently never having done it before.

[Wonderboy]

I think I should've taken a better picture of the seated new ring - there IS a teeny little gap you can see through, the ends do not meet.... so therein lies the dilemma. A VERY tight fit with one teeny hole probably 1mm wide at most, or a less tight fit with full closure. Hmm..

[Christ]

Normally, I'd tell you to use the new rings. In this case, I'm going to suggest that you either bite the loss, and buy a total seal ring kit, or you re-use the old ones.

Obviously, that's listed in order of preference.

[Johnny Mullet]

A standard ring set for a G10 would have worked. You just keep the extra rings for spares since you XFi only takes 2. Looking good so far.