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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...

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 .

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 .

FuzzyDriver said:

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...

Click to expand...

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

mower king said:

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

Click to expand...

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.

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 .

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

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 .

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.

This would have helped.

Hammermechanicman said:

CYLINDER PISTON RING COMPRESSOR TOOL KIT CHAINSAW FITS HUSQVARNA STIHL ECHO | eBay

Husqvarna, Jonsered, Echo, Stihl. Piston Ring Compressor Tool Kit. Includes 2 Piston Stop Tools. GET IT NOW. IT'S ON THE WAY! Quickest and Safest Ordering for you! Made in Italy.

www.ebay.com

This would have helped.

Click to expand...

Thanks for the link, Hammer. I can't say it wouldn't have worked, but the principle doesn't look much different than the hose-clamp suggestion that I saw and tried (but forgot to mention in my previous post). If I had it, I'd try it.

StarTech: As I said in my original post ("Following the tips in the service manual") I was already well aware of all this. Note that the only thing it says about piston installation is: "Apply oil to piston rings, wrist pin and cylinder. Carefully slide piston into cylinder." and it shows a photo with a label pointing to "Ring Compressor". Carefully slide piston into cylinder?! What were they thinking when they wrote that useless "tip"?? No part number given and, from other research I did, the compressor is not available anywhere. Before I started this saga, I printed my own copy of these pages and read them over and over, looking for anything useful with regard to piston installation. But there's nothing there. So no one is going to successfully insert their piston with this information. If you know of an easy, reliable method that works for future readers, please have at it! : )

I know you you following the instructions but you must read all of the installation instructions. The part that apparently didn't stick was the paragraph that instructed you to stagger the rings. The second sentence tells you to install the ring compressor. The showing inserting the piston shows that ring is assembly on the piston before installing the ring compressor.

BTW the ring compressor PN is given in the instructions I posted. PN 609967. It is about 84 usd plus shipping if available.

Now of course the manual don't give step by step instructions as they assume you have done this before, have a master tech teaching you, or at least you can think for yourself somewhat. Plus you got to remember these manuals are a lot times written by non technical personnel; therefore, they put in what they are instructed to do at times without questioning things.

It like the Hydro Gear BDP-21L I worked on yesterday. They don't give step by step instructions on how the assemble the pump. Apparently they didn't think about a tech assembling the pump cylinder while the pump is installed on the mower in the upright position. In that position every piston and spring falls out; unless, they are held in position. Do they tell how hold the those in, No.

How is that apparent? Does it have anything to do with how to get the piston into the cylinder? Please don't assume that, when talking about how to get the piston into the cylinder, I didn't read other parts that don't address that concern - like staggering the rings. The interesting part of the stagger instructions, though it doesn't have anything to do with how to get it into the cylinder, was that the stagger is to either side of the pin opposite to the exhaust side, since everywhere else you look it says to have the gaps 180º apart.

I've installed rings lots of times, just never in an engine that doesn't have a removable head before.

I missed the compressor part number. Sorry. Jack's Small Engines has it for 92$, but I've found listed parts on their site before that they didn't actually have. The Walbro carburetor air filter cover comes to mind. For $92 I could spend a lot of tedious time working those rings in, heh heh.

Well, the issue you ran into yesterday is yet another example of a poorly written procedure. I was a nuclear power plant technical procedure and surveillance writer. I'd have gotten canned if I left out significant things like that, regardless of the training that the technicians had gone through (and there is TONS of training they go through).

FuzzyDriver said:

Thanks for the link, Hammer. I can't say it wouldn't have worked, but the principle doesn't look much different than the hose-clamp suggestion that I saw and tried (but forgot to mention in my previous post). If I had it, I'd try it.

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These finger pinch type ring compressors make installing pistons and rings a snap.

So Fuzzy you thought of every possible way someone can do something other than a set way of doing things. That great. But I still think someone could still a way that you didn't think of. But what I was doing was probably never though of as to installing the cylinder with 8 eight pistons and springs facing down loose. They just fall out if you are not good enough to figure out a way to prevent it. With only about half inch on the sides you cant just use your fingers either or try to reposition the pistons once fall out of the cylinder as all 8 got to go in all at once during the insertion. It can be done with enough thought and engineering outside the service manual which was done for on the bench servicing only.

One thing I have seen is our techs nowadays just don't seem to use their brains to think outside the service manuals. Most can't even figure their way out a wet paper bag with both ends open; unless, it is shown in detail in a manual. Many of us older guys know that service manuals don't cover everything in 100% detail. Plus many pieces of equipment I work on don't even have a written service manual.

Most 2 cycles I do the piston insertion on are done from the bottom of the cylinder as many OEMs provide a built-in taper. Even then a pick type tool maybe needed to center up the rings. Actually using a compression tool would be very hard to remove after insertion as the lower crankcase is not fully open after the piston is inserted. Now of course I am referring to chainsaws and string/bush cutters engines.

As for the many 2 cycles that I have worked on they also have locating pins to prevent the rings from rotating. Here in the online 1978 F engine manual I see no indication that they are used so the rings would be able rotate while the engine is in operation. Grant it that the rings may never rotate much since it just mainly an up down motion. The pins I referring prevent the rings ends from getting hung in an open port. Actually I have only seen one two cycle Lawn Boy and it was such a piece of junk it was not worth the effort to just look inside the engine. I just sent on its way to be recycled. So I have no knowledge of how the ports inside cylinder are done.

Hammer those pinch looks like they will work according to image I have here of an open notch in the cylinder. Another way is a sleeve of aluminum with pinch tabs and a pair of long bent needle nose vise grips to pinch it very close to tight so the piston can slide into the cylinder. Might even be able to use the medical retractors I have here that I modified for in areas like this. I have also use soda pop cans for this as they are thicker gauge metal most times than beer cans.

FuzzyDriver said:

Thanks for the link, Hammer. I can't say it wouldn't have worked, but the principle doesn't look much different than the hose-clamp suggestion that I saw and tried (but forgot to mention in my previous post). If I had it, I'd try it.

Click to expand...

They work a treat as does the similar tools with a set of ratchet pliers to replace your fingers.
I inherited a set with the business

Now there was one question that has always bugged me
What are those 2 bent rods supposed to be used for ?

If it is the two I think you are referring to they are piston stops.

"One thing I have seen is our techs nowadays just don't seem to use their brains to think outside the service manuals. Most can't even figure their way out a wet paper bag with both ends"

Stop talking about me. I am offended.

The pinch type compressors work good for both top and bottom of cylinder piston insertion. Once the rings start in the bore the plastic will spread wide enough to take off the piston. If you work on a lot of stihl chainsaws two must have tools are these and a tool to install the brake spring.

Hammer Gee Whiz I was talking the younger generation [under 25] coming online. I recently had to try to get the JD Stihl tech to repair a hedger. He couldn't do a pressure/ vac test on it. Nor could find a bad spark plug that had it dieseling. I end having to fix it for my customer out my pocket to cover the warranty. So embarrassed that was the best they had for a tech.

I have did several Stihl chainsaws in the last few years and didn't really need the tool. For the brake spring may have used one my spring hooks here. I usually make my own so they are custom made for certain work. It sorta like the custom installation wrench I made to tighten up the oil drain on the Kawasaki engines. A regular crow foot will not work.

I still working on (in my head) on a spring hook tool for a Cub Cadet ZTR drive spring that is a royal pain to get on the hook tab. Luckily I only see these once every couple years so it is not a priority here.

Since my machinist retired I got to get my own lathe now so I can continue to design and make custom tools for my job requirements. It like the PTO clutch tool I use for torquing the mounting bolt when the Double D are involved. I now need a 46mm version.

Just kidding.
I have to agree with you on some of the new kids coming up unlike some of us old farts that grew up working on cars and such just don't have the mechanical background a lot of us take for granted. "Back in the day" we could work on cars and most other machinery with basic hand tools and a few specialty tools. Can't really do that today.
I have a little 4" Atlas metal lathe. I am by no means a machinist but it does come in handy making special tools and such

Yes back then it was a lot easier to work on our own vehicles. I right tracking a brake problem with my truck. It electrical in nature and I think I finally pin the are of the problem. It appears I have bad electrical connection in my steering column. As when they won't engage as if the anti lock is operating I can hit my fist on the steering wheel and it clears up. Still scary as heck when you need them to working right.

Years ago i had a problem with a dodge minivan not locking up the torque converter. Problem turned out to be a stuck thermostat. Not real intuitive to find.

StarTech: It's not just the Lawn-Boy you looked at. Unless I'm mistaken, there aren't any Lawn-Boys with pins on the piston rings. Nothing to prevent them from rotating.
Bert: What are "ratcheting pliers"? I've used large wire crimpers that ratcheted, but not pliers. Is this what they call Vise-Grips down in Oz?

They come in the ring compressor kit
I have 4 of them in different sizes because when you work on parallel twin engines with 360 deg cranks both pistons have to go in at the same time & tilting the barrels slightly to edge one ring in then tilting it the other way to get the corrosponding ring on the other side in generally results in a broken ring .
They are the same as the finger pinch ones but there is a pair of pliers to replace your fingers that have a stepped locking system like a hemostat because each ring covers about 5mm of bore variation . They have to lock so your hands are free to manipulate the barrels or crankshaft .

bertsmobile1 said:

They come in the ring compressor kit
I have 4 of them in different sizes because when you work on parallel twin engines with 360 deg cranks both pistons have to go in at the same time & tilting the barrels slightly to edge one ring in then tilting it the other way to get the corrosponding ring on the other side in generally results in a broken ring .
They are the same as the finger pinch ones but there is a pair of pliers to replace your fingers that have a stepped locking system like a hemostat because each ring covers about 5mm of bore variation . They have to lock so your hands are free to manipulate the barrels or crankshaft .

Click to expand...

Try as I might, I can't mentally picture an engine where you have to put the pistons in at the same time. What kind of bike is this??

mower king said:

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

Click to expand...

I bought a Lisle brand ring expander. Made in USA and <$10. It worked great, and thanks for the heads-up on that.

FuzzyDriver said:

Try as I might, I can't mentally picture an engine where you have to put the pistons in at the same time. What kind of bike is this??

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Every British Twin made from 1938 through to 1999
All the Triumphs , Nortons, BSAs Enfilelds Ariels & Sunbeams were 360 twins .

bertsmobile1 said:

Every British Twin made from 1938 through to 1999
All the Triumphs , Nortons, BSAs Enfilelds Ariels & Sunbeams were 360 twins .

Click to expand...

Thanks. I wasn't thinking about engines where there's no split along the crankshaft combined with cylinders that aren't separate.