Stihl 056av 56mm piston

[ELECT6845]

Will another 56mm piston work in this saw or does it have to be for an 056? Mine has some scratches on the exhaust side of the piston that you can feel with your fingernail. Saw did start and run but it was filthy so im tearing it down to clean it up. Should i try to rub out the scratches and just install new rings? The cylinder cleaned up very nice no scaring at all.

 

[ZeroJunk]

I bought an 056 56MM piston on eBay for $30 or so. Shipped from Canada, I can't remember who the dealer was.

I didn't see anything wrong with it. I used some brass shim stock as a base gasket to get the squish down to 20 thousandths or so.

But, I doubt it makes any noticeable difference from a stock base gasket provided you can find one.

Ran and cut great.

 

[ZeroJunk]

BTW, you say 056 AV. Make sure it is 56 MM. The only version of the 056 that was 56 MM was the Magnum II.

 

[ELECT6845]

btw, you say 056 av. Make sure it is 56 mm. The only version of the 056 that was 56 mm was the magnum ii.

its a 56mm so maybe someone changed it out before. The tranfer ports are spotless like it hasent seen use so i wonder what scratches it up? Thanks for the info.

 

[mtngun]

The tranfer ports are spotless like it hasent seen use so i wonder what scratches it up?

A pic would help, but scratches on the exhaust side are due to overheating, usually caused by an air leak or a fuel problem. It would be a waste of time to rebuild it without identifying and fixing the problem.

 

[hotshot]

OEM 56mm S056M pistons are hard to find, but there's one on FleaBay for
only $115

I bought one of those Canadian pistons too, but quickly returned it.
The wrist pin opening, up inside, was way larger than stock, over .060"
wider & not machined at all (as cast) and I don't know how the connecting
rod would stay centered up while running.

However, he honored the refund & claimed he'd never had a problem &
that had sold several.

 

[OREGONLOGGER]

056AV has the 52mm rings/piston..056AV Super has the 54mm rings/piston...056AV Mag II has the 56mm rings/piston these are the stock apps from STIHL. Those are the spec's for the 056 series...good luck!!

 

[ELECT6845]

Ok i got the piston cleaned up by using some wd-40 and some very fine sand paper. Only had to give it a few swipes and the scratches where gone. Now my problem is rings. If i measure mine they are 1.5mm and everything i see says they should be 1.2mm. I went ahead and ordered both sizes from northwood since they had good prices. Any help on the thickness wood be great.
Thanks

 

[Jacob J.]

All of the 056 pistons used 1.5mm thick rings. The regular "Magnum" also used a 56mm bore top end along with the Magnum II.

 

[ELECT6845]

Thanks for the info

 

[Piston Honda]

I know this is a super old thread but hear goes...
Anybody go ahead and use an 066 big bore 56mm piston, rings, wrist pin, and wrist pin bearing in the 056 56mm magnum. I know from experience that the wrist pin bearing for the 056 is impossible to find due to being odd sized. 13x17x14.5 and that is the reason for the switch to the 066 56mm piston, rings, wrist pin, and wrist pin bearing. The wrist pin bearing for the 066 is a much more common size at 12x15x14.5.
Any thoughts on this would be appreciated.

 

[fpwt]

I know this is a super old thread but hear goes...
Anybody go ahead and use an 066 big bore 56mm piston, rings, wrist pin, and wrist pin bearing in the 056 56mm magnum. I know from experience that the wrist pin bearing for the 056 is impossible to find due to being odd sized. 13x17x14.5 and that is the reason for the switch to the 066 56mm piston, rings, wrist pin, and wrist pin bearing. The wrist pin bearing for the 066 is a much more common size at 12x15x14.5.
Any thoughts on this would be appreciated.

Hey Dowdski,
Maybe you sorted this out already? One thought about changing to a different size wrist pin bearing is that you would then have to change the con rod as the piston end would not accept the bearing (old 17mm vs 066 new 15mm). That opens up another can of worms. Maybe there's a connecting rod with a smaller piston end that would fit the 056 crank and the 066 piston? Good luck.

I just picked up two saws: 056 Super and an 045 with hand written in magic marker "056 Magnum II". They both run, pistons look good but have 80 psi compression. Maybe my ancient compression tester isn't any good anymore...orings etc. I'l have to tear them down next winter and see if in fact the Magnum is a magnum.

 

[DZOUTCAST]

I know this is a super old thread but hear goes...
Anybody go ahead and use an 066 big bore 56mm piston, rings, wrist pin, and wrist pin bearing in the 056 56mm magnum. I know from experience that the wrist pin bearing for the 056 is impossible to find due to being odd sized. 13x17x14.5 and that is the reason for the switch to the 066 56mm piston, rings, wrist pin, and wrist pin bearing. The wrist pin bearing for the 066 is a much more common size at 12x15x14.5.
Any thoughts on this would be appreciated.

i just ordered a pop up piston and bearing after watching a youtube video on this very swap, the guy states his piston and pin are much lighter than stock due to newer design and the pin being smaller diameter. The bearing according to him, fits the connecting rod on the 056 and the pin for the 660/066 obviously because thats what its for. He meassure his piston and seen the skirt is .020 shorter than the 056 but doesnt free port the exhaust so he gains intake timing, he didnt state wether he was deleting his base gasket but i plan to do this, base gasket delete with pop up piston im gonna give it hell!

 

[eye.heart.trees]

So.....does this 56mm Stihl 056 piston fit the big-bore 660 top ends? Looks like it's about the right size, wrist pin is 12mm AFAIK....reallllly hoping to find a 660 56mm piston so I can use big bores and actually machine a bit more (w/o freeporting....on that note I'd love to know what the "concensus" is on what to do if you're in a position of having, say, 35thou squish but only 8thou of space before freeporting -- would you run the sloppy-loose squish w/o any freeporting, or would you deal with 7thou freeport so you could get your squish to 20thou? Quite literally in a comparable position with a build right now and I barely touched the exhaust floor I just gently did its ending/edging, didn't change shape or timing of the floor beyond what rounding the edge caused!)

 

[hotshot]

Big bore Stihl 066 pistons are plentiful aftermarket, so I’m not sure what you meant in your post “reallllly hoping to find a 660 56mm piston so I can use big bores and actually machine a bit more (w/o freeporting....on that note”.

Never tried using an aftermarket Stihl 056 56mm in an 066 big bore cylinder...the WPs are different diameters. But I’d be more leary of the compression deck heights being way different, as the crusty guy in the linked video never mentioned that part.

He also never mentioned the fact that the small end rod widths differ, so going your route may end up running the Stihl 056 wrist pin needle bearing tips unsupported and also allows the 066 con rod a lot of side-to-side play up top, not good if the 066 saw is a “rod centered” design. The 056M uses a 14.5mm wide bearing, the 066 is only 13mm.

As far as your free port versus squish compromise question, I’d adjust the free port to zero & just accept the 0.027” squish. For a 100cc saw, that squish will help keep the starter assembly in one piece!