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Husky 272 p&c size/ring size?

Started by smh, March 08, 2012, 09:30:22 AM

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smh

According to Husqvarna Service Manual the factory used three piston/cylinder combinations, marked "A", "B", "C".  Does anyone know if there was specific piston ring to match?
I want to re-ring my engine but find only one ring part number reference (Jacks Small Engines).
Any info on this appreciated. Thanks!
Steve
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

smh

wow, did I stump the stars? No worries. I went ahead and ordered a factory ring. I'll mic it, compare to what is on there now.
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

Cut4fun

I havent a clue but will render you a guess. 52mm by 1.5mm

smh

Thanks Cut4Fun. Your guess is better than mine. I'm just wondering if the factory sized the ring to match the different piston sizing? IOW, are there three different ring sizes, or, just 'one size fits all'?
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

Cut4fun

I'm not the one to ask and I dont know these saws even though I own one. But I have only seen 52mm 1.5mm rings offered.

bandmiller2

SMH,I would say the A B C thing is more for the factory assembly so they don't have to hold too tight tollerances,besides the Sweeds have this thing about tite fitting pistons.The first Volvos in this country were set up to breakin on sweedish roads when the yanks got them on the interstates they would seeze up they had to relax their tollerances. Frank C.
A man armed with common sense is packing a big piece

NCFarmboy

It is 52mm x 1.5 mm.  There is only one ring for 272 works in a,b,c cyl.  Before maching tolerences were improved upon they used to piston match to cyl. hence A,B,C cyls.  Later models (improved machineing) do not require piston to cyl matching.  OEM PN: 503-2890-19 works in 272-272XP.
Shep
Lots & Lots of Saws

smh

Great info guys. Here's the deal: I was sold a mismatched 272 p&c. The tell-tale was low compression and so-so power.The cylinder is grade C (the largest), the piston is marked AB.
According to Husky service manual it's ok to match a bigger piston to worn cylinder, but not vice versa. Since I have a C cylinder, I need at least a C piston. However, the info from NCFarmboy suggests I should maybe just buy a new piston and ring, call it good enough :-)  Probably what I'll do.
Again, thanks all!
Steve
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

Al_Smith

FWIW Husqvarna was not the only company to use different bore grades .McCulloch did the very same thing on several of the 82 cc models .

Although it might be debatable my opinion on the situation was they could not accurately get the bore sizes all the same because the technoligy did not exist as it does today .As such they were able to get the tolerences to fall within three bore grades .Sizing the piston was not a problem .Now in the case of Mac it was a difference of around 4 thou from the smallest to the largest .They listed the same size piston rings for all of them though as I suspect Husqvarna may also .I'd imagine that given enough time the rings  might have seated on this piston /cylinder miss match but it would take a spell .

On this bore grade remember this is a plated cylinder .Fact being having worked in or around the auto industry for around 40 years it was only in the last ten-12  years they could get all the cylinders exactly the same and they are cast iron .

They solved that with different bore grades .They all did it GMC,Ford ,Honda .Now of days they can cut them with micron spectifications ,all pretty close to the same. A micron is one thousanth of a milli meter .Finer than a frog hair .

Keep in mind these or automotive bore grades are not to be confused with over bore sizes .These bore grades are only around 2 thou difference if that .

smh

Al_Smith, that's interesting. So then the .006-.007 piston-to-cylinder I'm reading is definitely out of tolerance? How about one of the cheap aftermarket pistons? Would that be a workable solution? I just want the engine to perform like a 272. As it is now, it more-or-less feels like my buddies stock 61. Mostly less...
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

Al_Smith

How much run time do you have on it???

I've got a Stihl 038 Mag that had some slop in it .Reringed it ,hopped it up a little .It took me all of one summer to get the rings to seat .The reason for that was cutting down out of a giant stack of oak 10 minutes at a time and never really putting an extended  load on the engine .

It runs like a scalded ape now after it finally came in .

I have no idea what the skirt to cylinder clearance is supposed to be but would guess around 4 thou .When I get a chance I'll look up the Mac specs which is about all I can do because I only have Husky IPL's and not the tech specs .

So it's up to you .I personally think if it hasn't had much run time it will come about all my it's self .It's going to take time though .

Al_Smith

From what I can see using standard tollerences the Macs were as I said around 4 thou .That's brand new though as they came from the factory .

All I could find was service manuals on iron cylinders ,none on chrome so I have no idea how much slop they can have but on iron it can go up to 5 thou over max .

So if you have 6-7 thou and around 3.5 -4 thou fit is within specs I wouldn't think a couple over would be so bad .

smh

This is a used p&c (plus carb) top end I put on a stock 61 crankcase. Both p&c definitely have been used. How many hours?.. who knows. But my 61 (with roughly 250 cord on it) looks brand new by comparison.
What bothers me is the piston/cylinder mismatch. The factory obviously wanted a certain tolerance. I have no experience in air cooled but .004 you mention seems reasonable.
Note: ok, ok, got dressed, went to the shed, measured the 61 piston at 1.885, the cylinder at 1.889. So you hit it: four thou is what you want.
I do have a new ring coming from JacksSmallEngine (back-ordered). But now I know for sure I need a tighter piston. How about an aftermarket piston. Not them $100 factory OEM's, but one of the cheap $25 buck jobbers. Any experience using these?
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

NCFarmboy

Aftermarket are fine.  Get a Meteor, Episan, NWP (not too bad).  Meteor 1st choice.  Use them all the time as OEM is too expensive.  Try Northwood Saw (Meteor), Baileys (NWP), Ebay dandrikop (Meteor, Episan).  AM rings Caber only!
Shep
Lots & Lots of Saws

Al_Smith

FWIW I resleeved a Mac 125 with a cast iron liner a number of years ago .Fact I think I'm the only one ever to put pictures of the process on the internet forums .I had it set 4.5 thou and finished it with a Lisle precision hone .

Now that thing has less than 1 hours running time on it .It has nearly the power of another 125 I have but can be started without the decomp which is unusual if you've ever pulled a 125 over .So on that one as well I believe the saw in question it's merely a question of some run time .That's just an opinion and believe me they do vary .

Although most people would prefer the innards of the engine to be flawless there are many with slop in them that have cut well for years and will continue to .I would not recommend running gas/oil mix at a hundred to one but people will debate that too so I'll drop it before the oil wars get ignited again . 8)

smh

Follow-Up:
I bought a new 52 mm Meteor piston from Northwood Saws, $37 (thanks NCFarmboy for the link). It measures .0035 larger o.d. than the piston I bought used as a p&c set.
I'm not going to hone the cylinder because I'd have to purchase a hone, and I'm already into this for more $ than I intended. I can do that later if necessary.

Here's the good part: I immediately noticed the pull rope harder to pull. Sure enough, compression is up ~18 psi! That's as good as I can pull left-handed.
It will be interesting to see if the new ring can seat to the used cylinder. If so, I'd expect to see a further compression increase.
oh, fyi: Northwood Saws is in the process of replacing the Meteor line with Episan. According to the sales dude, I got one of the last Meteor in stock.

This has been a fun and informative project for me, something to keep me busy while I recover from arm surgery. It proves the value of having proper tolerances.
Thanks to all of you who chimed-in, helping me with your greater experience.
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

NCFarmboy

Don't worry about not honing.  The new ring will seat to used cyl. and comp. will/should go up. There are 2 schools of thought on honing so say no some say yes.  On a Nikasil plated some say a flat NO.  It depends on the condition of the cyl whether I hone or not.  If I do I use 320 grit ball/Flex hone.  Lightly!  I stress lightly as you can hone through the plating.
Shep
Lots & Lots of Saws

smh

hmm yup good point. my engine experience doesn't include saws. Thanks again for the advice Farmboy 
husky 61   -   old school mods
husky 272 -   heavy metal mods
husky 4 parts-uh oh oops
stihl 180c  -   what will it be when it grows up?

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