Compressing the two rings...

[mrcaptainbob]

 How can I compress the two rings to get the piston back in the cylinder? The automotive one I have is too large and unwieldy for the job. A hose clamp? I don't do this a lot.

[doc henderson]

good idea.  they make them of course for small engines.  I have a couple but you are a ways away.  good luck.  I did it by hand when i was a kid on a 60 cc Yamaha.

[Old Greenhorn]

Take a plastic coffee can and cut it open and make a 2" wide strip, wrap it around the rings and put a hose clamp on it near the base, then with a block of wood drive the piston into the cylinder with a soft mallet. 
 Usually I can get small rings into the cylinder with my finger nails alone, but it is funny to watch and you shouldn't really have children present when I do it. :D :D

[doc henderson]

If children are present, safety first!.  always have them use hearing protection and cover their eyes if @Old Greenhorn is doin something tedious!   :D :D :D ;D ;D ;D  If not, they say it is good to learn sign language, and know a foreign language.

[Real1shepherd]

ebay, Bailey's and a lot of places are awash with little plastic 'helper' ring compression kits for chainsaws. Not much money as they're all plastic.

Maybe try one of our sponsors.

Kevin

[sawguy21]

I use a worm drive hose clamp, not as quick as the plastic ones but works and is readily available.

[sablatnic]

I normally use piece of a steel packing strap. 

[Al_Smith]

The cylinder should have a chamfer on the bottom .Oil everything up and if you hold your mouth just right the piston will slip right in .Joking aside that's how I do it .If the piston has pins make sure the ring gap is on them else you couldn't beat it in with a big .hammer .
The key to it is oil .Don't use wd-40 or something. Regular old crankcase oil ,brand makes no difference .If it doesn't blow smoke for a couple of minutes on a start up you didn't use enough .

[old guy]

If your not using those little red ring compressors, your doing it the hard way.

[Tacotodd]

I don't know if it's been mentioned or not, but a soda or beer can that's been slit to where it's only the thin part left (no rolled & thick parts) would be easily manipulated and removed when you want to remove the can. Just wrap it around the piston and rings and you're there. Bass-bing bada-boom, done. Seat the cylinder and continue with the re assembly. Easy to trim the can to fit, if it's to much can (2"x4" should be plenty)  it can easily be trimmed with scissors. It's slightly hard on the scissors, so have a dedicated pair for the less than precision use such as this. Sheet metal shears or tin snips or even cheap aviation snips that I've sold in a three pack of different curvatures for about $25 would be spectacular ;) Just don't use the best ones in the house! A better half that's OCD might, ahem, complain when they no longer cut like they did.

Full disclosure, I'm the one in our marriage that gets OCD. But I don't believe in trashing what you have either    My wife will disagree, but that's why I want high quality stuff from the begging. Cry once at purchase, not every time you use or break, & then have to purchase again!

[Fishnuts2]

You'll pat yourself on the back after you buy one of those Husqvarna branded ring compressors.  I even give them as gifts once in awhile.
They're around $10 and also come with 2 plastic piston stops and a piece to hold the piston stable while installing the rings.

[Al_Smith]

I think too many people are painting with a very broad brush .It's one thing on a chainsaw with a removable cylinder and entirely another on a clam shell or for example a reed valve McCulloch . What ever floats your boat though . ;D Saying that I've never used a ring compressor on any small engine and I've worked on a lot of them .
Now on an old diesel like a Caterpillar with 3 or 4 compression rings and two oil rings that's entirely another  subject .Big thick rings almost impossible without a compressor . On those I have compressors I think up to 5 or 6 inch .

[Mad Professor]

Make a piston holder from a piece of 1" scrap.  Lube up the cylinder/rings and get the crown started, then I make a tool from an old toothbrush to work the rings in along with your fingers.  Things go much easier with the piston support. I'd avoid any hose clamps as the steel can mar the piston.