I have been told that when I replace the rings on a Lawnboy, I should hone the cylinder to help the rings seat. Can somebody give this self-taught Lawnboy mechanic some instruction on how to do this? What type of hone to use, what type of lubricant to use when honing?
Queston about honing a cylinder
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I have never replaced a piston or rings in a cylinder. I will be replacing two pistons this fall so I have done some research. I have found that the two or 3 stone expanding hone works better than the round ball type. There are many different sized hones and that you need one that will fit the bore you are working on. The speed of the hone spinning is another issue. Have not gotten much on the ideal rpm only that you do not want to spin too fast. Number of passes is also a concern, less is better. What kind of oil or lubricant is another I do not have any kind of information on. Probably not much help hopefully someone that rebuilds motors will reply.
BlazNT
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Lots of YouTube videos on that subject. You really need to watch it to understand it.
Hello,
I've never honed the cylinder of a Lawn-boy, but I have rebuilt the engine on a Sears Gamefisher (Tanaka) 3.5 air-cooled outboard. I used a brake cylinder hone and a hand drill. As stated, Youtube does show how to perform honing. The trick is to keep the drill speed slow and move in and out of the cylinder quite rapidly. You shouldn't perform this procedure for that long, maybe a minute or two. You are just deglazing the cylinder and introducing a cross hatch pattern of 30 to 40 or so degrees. Use WD-40 or motor oil as a cutting fluid. Don't stop the hone in the cylinder and remove it, keep the drill spinning as you withdraw it from the bore.
The Outboard ended up with a cold compression test of 103 PSI,,,I guess not too bad for such a small piston. Most weed whacker engines I have only pull about 80 PSI
Jeff
I've never honed the cylinder of a Lawn-boy, but I have rebuilt the engine on a Sears Gamefisher (Tanaka) 3.5 air-cooled outboard. I used a brake cylinder hone and a hand drill. As stated, Youtube does show how to perform honing. The trick is to keep the drill speed slow and move in and out of the cylinder quite rapidly. You shouldn't perform this procedure for that long, maybe a minute or two. You are just deglazing the cylinder and introducing a cross hatch pattern of 30 to 40 or so degrees. Use WD-40 or motor oil as a cutting fluid. Don't stop the hone in the cylinder and remove it, keep the drill spinning as you withdraw it from the bore.
The Outboard ended up with a cold compression test of 103 PSI,,,I guess not too bad for such a small piston. Most weed whacker engines I have only pull about 80 PSI
Jeff
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Just a word to interested parties...the honing creates a new surface with a pattern that holds extra oil during new ring break in. I think kerosene is also used. One golden rule from hot rod lore. After honing USE HOT SOAPY WATER AND A SCRUB BRUSH TO THOROUGHLY CLEAN THE BORE OF GRIT. RINSE WITH CLEAN WATER AND WIPE WITH A WHITE RAG. Oil afterward to avoid rust. This is hot rod gospel, I forget the verse...:thumbsup:
Motoman hit it on the head before I could. The only thing I would add is I use a ball hone instead of a three leg expanding hone. Easier to control and you don't have to worry about setting stone pressure. Don't use a brush, just a rag, but I also wash it twice. You don't want any leftover grit in you engine. I like a spray can of oil (WD-40, PowerLube, etc.) at the ready to stray down any machined surface ASAP after drying. Compressed air first then the white towel, any dirt on the towel, START OVER.
bertsmobile1
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And a quick word on stone grit.
Cast iron barrels with cast iron rigs require a really rough hone 180 grit or coarser.
I do a lot of old Pommie motorcycles and they get 120 stones as bottle brush hones do not go that coarse.
Too fine a hone and the rings will never seat properly.
You will get good compression but blow a smoke screen James Bond would be proud of.
Assemble the rings into the bore with no oil.
A touch of starter fluid or carb cleaner if it needs a little help.
Try not to leave the re-ringed engine idleing for more than a few seconds.
Assemble the engine into the mower start the engine and push it into some long grass they will put a heavy load on the engine.
This builds up pressure behind the rings and they will seal in a few seconds but mow for 10 minutes or so to do the job properly.
Now that the rings have sealed start to play with the carb it will need adjusting if it has been adjusted to compensate for the old worn out rings.
Too many failures come from people spending 20 minutes buggerising around with carb settings with the engine on low idle most of the time happily glazing the bore.
Don't worry if it runs rough , misses, backfires ( a little ) just so long as the throttle is wide open and there is a load on the engine.
The load is really important or the engine overrevs and again glazes the bore.
While mowing it is beneficial to open & close the throttle .
Been breaking in engine this way for 20 years and never had a failure once I changed over to dry installation.
This only applies to castiron rings running on castiron bores
A whole different ball game with steel rings or chrome plated bores
Cast iron barrels with cast iron rigs require a really rough hone 180 grit or coarser.
I do a lot of old Pommie motorcycles and they get 120 stones as bottle brush hones do not go that coarse.
Too fine a hone and the rings will never seat properly.
You will get good compression but blow a smoke screen James Bond would be proud of.
Assemble the rings into the bore with no oil.
A touch of starter fluid or carb cleaner if it needs a little help.
Try not to leave the re-ringed engine idleing for more than a few seconds.
Assemble the engine into the mower start the engine and push it into some long grass they will put a heavy load on the engine.
This builds up pressure behind the rings and they will seal in a few seconds but mow for 10 minutes or so to do the job properly.
Now that the rings have sealed start to play with the carb it will need adjusting if it has been adjusted to compensate for the old worn out rings.
Too many failures come from people spending 20 minutes buggerising around with carb settings with the engine on low idle most of the time happily glazing the bore.
Don't worry if it runs rough , misses, backfires ( a little ) just so long as the throttle is wide open and there is a load on the engine.
The load is really important or the engine overrevs and again glazes the bore.
While mowing it is beneficial to open & close the throttle .
Been breaking in engine this way for 20 years and never had a failure once I changed over to dry installation.
This only applies to castiron rings running on castiron bores
A whole different ball game with steel rings or chrome plated bores
bertsmobile1
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Chrome , no
Chrome is micro cracked. It looks like a dried up mud flat and these cracks hold the oil that lubes the bore it is also why you should apply a chrome wax to decorative chrome.
Nickasil is another ball game again.
It is very very very hard and should be used in conjunction with soft rings.
Never had to work on a nikasil engine bore. Only place I come across it is drum brakes which have to be rotary ground back to round.
Chrome is micro cracked. It looks like a dried up mud flat and these cracks hold the oil that lubes the bore it is also why you should apply a chrome wax to decorative chrome.
Nickasil is another ball game again.
It is very very very hard and should be used in conjunction with soft rings.
Never had to work on a nikasil engine bore. Only place I come across it is drum brakes which have to be rotary ground back to round.