I've been rebuilding an 084 that was given to me that had been run over. I've been working on it off and on for 6 months. I put all new Stihl or oem parts in it, from Stihl, crank bearings, crank seals, rubber, complete gasket kit. The cylinder looked good to me, piston too, so I put new Caber rings in it.
I got it to running, but, it wouldn't run right, so, I let a friend work on it. Actually he is a much better tuner than I am. He's got a world of experience in small motors and chains saws. He couldn't get it to running right, even after a new carb kit. Now he tells me that it needs honing, because when he pulls it over, he says it's losing compression about mid way up the bore. He thinks the cylinder is egg shaped. I can't remember, but, I think that you are NOT to hone a Stihl cylinder account of the nickasil coating, am I right about that?
I wouldn't do it for that reason. Can you pressure/vacuum test the crankcase for leaks?
sawguy, Not now, he had taken the cylinder off to hone it before I found out what he was about to do. That's another thing that concerns me, he should have done a pressure/vacuum test first, I think.
It's unlikely the cylinder is egg shaped because the coating on the cylinder is so thin, it would wear through before it actually became out of round.
Bailey's sells a ball hone for cylinders. Problem is that it must be done 'fast & sweet'....you don't want the balls affecting your transfer edges. Were there any aluminum transfers in the bore? Did you run your fingernail across the bore surfaces? If the cylinder was actually out of round, a honing won't help, because as I said, there is not enough plating material to work with.
The cylinder can easily be checked for concentric issues. It's hard to armchair this without seeing the saw....lots of things it could be. Did anyone do a compression check on the saw? Does it hold a pressure & vacuum test?
Kevin
I'm not an expert on chainsaws, but back in the day during a rebuild we would make a light hone pass on automotive cylinders in order to "deglaze" them, so that the rings would seat better.
This was typically done using a drill, at an up and down pace that would provide a 45 degree crosshatch in the cylinder. Typically it would require around 15 - 30 seconds per cylinder.
I wonder if this may be part of your problem?
Real, I rebuilt the saw and there was no aluminum transfers in the bore. The cylinder bore looked almost new. I think it was a low time saw before it got run over, and since saws like that are used by professionals, they couldn't wait for it to be repaired, so just bought another one. And this one went on the dealer's keep for spare parts shelf. But, it was complete when I got it, except no bar or sproket cover. No compression check with a gauge has been done on it since I rebuilt it. Unfortunately he pulled the jug before doing a pressure or vacuum test. You've all been very informative on the cylinder, so, I'll get the saw back and put it back together and then do a pressure and vacuum test, and go from there. There are too many negative to honing it according to the response's, so, I'll put it back together without honing. Thanks to everyone that responded!
I usually do a light ball hone, maybe 5 seconds one way and 5 seconds the other just to smooth out what was done mostly with sand paper and my finger. Then I put it in the dish washer.
If you have an old cylinder around you can take a ball hone and see how long it takes to start wearing the plating off the down wind side of the ports and transfers. Takes a while.
But, as far as honing some out of round out of a plated cylinder, that's nuts.
BTW, neither the piston nor the cylinder are actually round to start with.
Quote from: 421Altered on August 27, 2020, 12:37:31 PM
Real, I rebuilt the saw and there was no aluminum transfers in the bore. The cylinder bore looked almost new. I think it was a low time saw before it got run over, and since saws like that are used by professionals, they couldn't wait for it to be repaired, so just bought another one. And this one went on the dealer's keep for spare parts shelf. But, it was complete when I got it, except no bar or sproket cover. No compression check with a gauge has been done on it since I rebuilt it. Unfortunately he pulled the jug before doing a pressure or vacuum test. You've all been very informative on the cylinder, so, I'll get the saw back and put it back together and then do a pressure and vacuum test, and go from there. There are too many negative to honing it according to the response's, so, I'll put it back together without honing. Thanks to everyone that responded!
I just don't see tragically out of round cylinders in chainsaws...the plating would wear through first.
You can go on You Tube and there's what's called the 'wigglesworth method'. A guy named Randy ports saws and is very well thought of in the biz. He shows you exactly how to polish a chainsaw jug without honing. The 'wigglesworth' part is using a rubber mandrel that's just under the size of the bore...then you take some brown Scotchbrite pads cut a piece a little bigger then the mandrel and using a drill, force it down the bore up and down like a hone. MUCH safer than a hone and you can polish until you get the desired results.
Turning the jug upside down with the spark plug in, drop the piston into the bore without any rings. It should float down to the end of its travel. If not, something isn't Kosher so start measuring.
Kevin
My uncle used to talk about people who could destroy an anvil with a cooked colla flower, about the same talent it would take to destroy a cylinder with a hone.
https://www.youtube.com/watch?v=VuMlesup53o (https://www.youtube.com/watch?v=VuMlesup53o)
Watch Part 1 and Part 2. 'Wigglesworth' method explained in Part 2.
Randy is unquestionably the most honest port man in the biz. I respect his methods and his techniques. So do the hundreds of people who own his ported saws and the hundreds waiting for theirs to be done by him.
Kevin
never hone a cylinder , if you have to use a flap wheel . the cylinder coating is only a couple thousands thick and never seen a cylinder go out of round . If he is hearing something like compression then maybe the decompressure is leaking or did the cylinder get cracks when ran over . Also make sure crankcase is not leaking or gasket between cylinder and crankcase
Thanks to everyone that has replied to my post. All of y'all have given me things to look for that I didn't think about before. There is truly a WORLD of knowledge on this site!!
I've got a Lisle precision hone which is the only type that will actually round a cylinder .A shoe or ball hone will just follow the shape of a cylinder not correct it .If any thing some 3M greenies and a hand sand lightly is all I would do .It could be out of round but in time the rings will seat with just some run time .
Some ten years ago on a rebuild and modification of a Stihl O38 Magnum it took me half of a summer before it really came to life cutting ten minutes at a time a big pile of oak. Don't lose your cool .Some run in quickly some just take longer .
Now on rings seating .like I said some are quick .The two Partner P-100 I just did are there already on about a half a tank of fuel and they both got D-handles very quickly .Danged things try to pull your fingers off .Easiest large saws I own for starting too . Those,Swedish made use Mahl cylinders just like Stihl and in spite of their age looked nearly perfect after I cleaned them up .I didn't even use Scotch Brite on them .
Now the Lisle hone which was given to me is not something a person would find very often because of the cost involved .The way they are made they will correct for taper and ovality .Generally speaking seldom used on plated cylinders .I've got both the cast iron stones and stones for plating but have only used it once .That was for a cast iron liner I made for a rebuild of a McCulloch 125C the plating had flaked off .It came in less than half a thou in taper and ovality .With the tool steel piston rings some 12-15 years after I haven't put enough run time on that engine to seat those rings .It runs very well though in spite of that
As I said, with chainsaw jugs the plating is so thin that unless the saw got run over by a skidder or truck, out-of-round cylinders are just not an issue.
Lots of guys just throw in new Cabers and go forward(I'm not advocating that) with a pretty good success ratio. I'm old-school and prefer to at least polish the plating and at the very least remove all traces of aluminum transfers.
Most Caber rings are broken in by 4-5 tankfuls....you can monitor that with a compression gauge.
Kevin
If you have enough oil in the gasoline and set the carb correctly it's doubtful you would get .any transfer .Now ingestion of dust,grit from a faulty air filter or scorch from a lean mixture or highly restrictive muffler is another story .There you could get transfer .
I've torn down 50 year old chainsaw engines that had no transfer .Oil,the life blood of any engine .
Back in the day when we regularly used leaded gasoline piston melt downs were alot less frequent.
Reason why the aviation industry still use it in their fuel today.
Here today we have leaded gas been eliminated for ground use but still have it raining down on us from the aviation industry.
Well, I wasn't saying that aluminum transfers are common to every saw that's aged. I've never seen transfers in any of my saws and many are in their 40's.
There's a reason transfers happen.....usually an oil mix issue, but not always.
Kevin
I just reminded myself about the 108 octane VP C12 race fuel I'm running in my bikesaws , it's leaded too.
There for a reason....