Piston Ring Installation

[FuzzyDriver]

Following the tips in the service manual, I was as careful as I could be removing the bottom ring from an F-engine piston and broke it anyway. Anybody have a good tip to keep from breaking these? Maybe heating the ring? Freezing the piston? Some sort of magic lubricant? I'd really like to NOT break the new ones when I put them on...

 

[bertsmobile1]

Put 3 feeler gauges about .005" on the side of the piston then lube them so you can slide the ring over them
slide the ring over the groove then pull them out 1 at a time while holding the ring in place .

 

[SeniorCitizen]

When a ring breaks removing I determine it wasn't of much value anyway and time to replace it. Lowe's shows brass sheet material that can be made into a entering sleeve . In the natural gas compression world it would be called a horse cock to protect pressure and wiper packing while installing a piston .

 

[Mower King]

Following the tips in the service manual, I was as careful as I could be removing the bottom ring from an F-engine piston and broke it anyway. Anybody have a good tip to keep from breaking these? Maybe heating the ring? Freezing the piston? Some sort of magic lubricant? I'd really like to NOT break the new ones when I put them on...

They sell a hand-held ring expander tool....they are cheap to buy.

 

[FuzzyDriver]

They sell a hand-held ring expander tool....they are cheap to buy.

Are you suggesting a tool that expands the diameter of the ring larger than the diameter of the piston so it can be removed all at once?? Just pulling one end over the top edge and working carefully around a little at a time (i.e., so the ring was never larger than the diameter) was enough to break it.

Hmmm..unless it broke because of the little twist, as opposed to the end separation. ??

When a ring breaks removing I determine it wasn't of much value anyway...
SeniorCitizen: I never intended to reuse it, being careful was "practice" for the new ring installation.

Bert: Your suggestion seems pretty close to King's, but with using stuff I have on hand. I think I'll give it a try on another piston and let you guys know if avoiding the twist (going with diameter stretching) works.

 

[bertsmobile1]

Yes Fuzzy
a ring will open out quite a long way without breaking
However a very small amount of twist and it is all over .
They are designed to get bigger & smaller so will happily do just that .
using a ring expander does exactly that and you need a ver small amount expansion to get it over the piston

If using 3 feeler blades , lengths of beer can ( or similar ) , the trick is to lift one end squarely out of the grove with a pick, small screwdriver etc
Once the ring is high enough the feeler is slid under , then moved around the piston to the other side.
Then the gap end of the ring is lifted again and another is slipped in and moved 1/4 the way around the ring
Then repeat on the other side
You need to keep 2 of them fairly close to the gap because it is the gap edge that will tend to get caught.
You can use more than 3 strips, it depends on the diameter of the piston but being a Lawn boy I would assume the piston is around 1.5".
Some wrap the whole piston with beer can or you can use some stiff plastic or even business cards .

 

[FuzzyDriver]

Thanks for taking the time for that detailed write up. Just FYI, Bert, Lawn-Boy piston diameter is 2-3/8".

 

[bertsmobile1]

Interesting side note for me but we did not get Lawn Boys down here
They tried a couple of times but they were a 100% market failure against the locally made mowers which were both cheaper & substantially better for local conditions.
Back then we were a nett exporter of walk behinds , how things have changed .

 

[FuzzyDriver]

I tried a whole bunch of ways to get the piston in and finally got it. I bought a Lisle ring compressor and that was a total waste of money. Packaging said it could get down to 2-1/8", but at that size it was not going into the cylinder. Even worse was the fact that it was designed to push a piston in from the top, which obviously doesn't work with a Lawn-Boy.

Next I tried poking and prodding the piston rings for a good while. This not only didn't work, it got me really irritated.

Then I went to the party store and bought a Fosters. To give it the best chance of working, I downloaded the Fremantle Dockers jock-jam and watched last September's Dockers vs West Coast Eagles game while drinking the Fosters (Dockers won). The Fosters was very nice. I cut up the (now empty) can and made a ring compressor out of it. This not only didn't work, I broke the top ring trying to drive it in. I think this had a lot to do with the tiny, specified ring gap. .007 to .017 means it hardly fits in the cylinder without a layer of Australian Aluminum around it.

What finally worked was getting the piston perfectly straight in the bore, top (second new) ring touching the insert all around, and then spending an hour slowly working a little bit at a time under the insert's edge with a tiny tweaker (.094" wide, .023" thick on edge), then doing the same with the bottom ring. So the Fosters did help, just not the way I expected, heh.

 

[Hammermechanicman]

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This would have helped.