Topic: replacing the rings

[eigenvector]

A little scary just how easy it is to remove and replace the rings on a 550.  While probably not the preferred method, simply grabbing it with needle nose pliers is sufficient to spread them apart enough to slide them off.  I'm glad it's easy, but it sure is uncommon.

I noticed the 2nd oil ring was broken on the #2 and 3 pistons.  Fortunately I have a scrap engine to scavage from.

As to installing the pistons, I'm using a hose clamp as a ring compressor and lowering the cylinder onto the piston.  Is that not a good idea, should the pistons drop into the cylinder and the install the wrist pin?  Seems like the bottom of the cylinder sleeve is beveled to alllow installation from underneath.

[calj737]

Lowering the cylinders onto the piston is the preferred method. You can also use some wooden shims to support the jugs while you orient and align the pair of pistons into the cylinders and then rotate the crank and align the next pair. Avoids chipping the edges of the sleeves.

Re-using rings from another set of pistons is questionable. You at least need to measure the end gaps and clean both the piston grooves and ports and the rings from gunk.

[flybox1]

ring compressors, like you are using, work just fine.
just be sure the clamps have no burrs scratching the pistons as you slide them down.  I used a thin plastic strip between the rings and the clamp...
light oil on the inside of the cyl helps, too...
new rings would be preferrable.

[eigenvector]

Check the clearances on the rings?  I don't know where you do your work, but I wrench on my bike under the shade of a tall tree.   (Actually that's a literal truth, it sits under a big Douglas Fir).  Your comment about the rings is understood, I'm not really worried about it for the moment, this is an engine that I'm doing some testing on.  The bike doesn't even have a wiring harness.

That said, I have a new bottom gasket and rings on order for when I do put it all back together - properly.

[calj737]

Just like you actually, in the gravel under the trees. Ring end gap is measured prior to piston installation. Sounds complicated; it's not. Use a feeler gauge and be sure the ring is usable before spending the time to assemble your engine. Test or not, it's not very viable if it's doesn't run worth a darn, and shot rings will lead to very poor compression and poor combustion. Hard to test anything with that going on inside.

Plenty of YouTube videos out there to show the tricks to doing it just like the pros, without the A/C and steel building. 

[eigenvector]

Testing, when I say testing I mean turn the crankshaft by hand.

Remember that post I made a long while ago about printing a new cam chain return guide?  Well I have a bunch of prototypes and I'm just manually turning the engine to check fitment, see where and if they're hanging, where they're likely to wear, small tweaks.  Not even sure why I bothered replacing the oil rings, other than I saw them and it bothered me.

[calj737]

You don't need pistons or rings for that...

[eigenvector]

Let's say I do remove the pistons, can you substitute snap rings for the wire retainers that are used right now?

Personally I find snap rings easier to install than wire retainers - but I have snap ring pliers.  Seems like those wire retainers always want to shoot off in random directions, typically just before you're about to finish.