Stihl 066/660 with an 056 Super piston?

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SGaron

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Hey everyone, I've been rebuilding a Stihl MS660 and I'm about to the part of getting a piston to throw in it (piston cracked from previous owner failing to buy a piston stop), and I started thinking about how I see other people transplanting pistons from huskys to stihls and vise versa, and it got me thinking. Long story short, I found one post buried in here about putting a 52mm 056 piston in an 064, and that it might can be done, but takes some decking to the cylinder and the issue with the wrist pin's being different sizes. I've got a few 54mm 056 Super pistons over here that I'm doing nothing with and I was wondering if anyone could shed some insight on how to get this to work. I've read up on the different strokes (38mm vs 40mm) and it seems doable with the right know-how. I'm still a newb when it comes to this area of mods, and I think it'll be a pretty fun project, but I need some help. Thanks again everyone.

- Shane-
 
What he said is a valid point It is possible to sell or trade the 056 pistons for the pistons you need.

Sent from my E6810 using Tapatalk
 
I hate bumping an older one but it's precisely what I'm looking to understand- Does the Stihl 056 cylinder & piston setup fit onto a 660? Bores aside, am talking about for instance cylinder bolt-up, and - most importantly to me - whether an 056 piston will sit on a 660's connecting rod?

I'm also curious why I'm seeing 52mm all the way to 56mm for 056's....had always (wrongly)assumed it was some unrelated model but it seems it's "part-related" to the 066/660 line and I'm curious for all anyone is willing to share but most interested in whether the piston will fit a 660, because they (lil red barn) sells 56mm 056 pistons that are just beautifully domed and definitely have longer skirts than the big-bore 660 56mm pistons do (which is my setup right now on one of my units) and if I could just use the 56mm 056 piston - even if I've gotta do a lot of work ot it - if it just fits that connecting rod I'm set, I'm happy machining the crown and even going single-ringed I'm just not setup to alter the gudgeon/wristpin so it needs to be "plug&play" fitment to the 660 connecting rod!

Thanks a ton, the piston's most important but I actually am very curious about the 056, for isntance if I had 056 jugs - 52mm and 56mm ones - would both, either, neither of them fit a 660? To be crystal clear, I'm only talking about fit, not "will it work if I just drop it in?" yknow!
 
I hate bumping an older one but it's precisely what I'm looking to understand- Does the Stihl 056 cylinder & piston setup fit onto a 660? Bores aside, am talking about for instance cylinder bolt-up, and - most importantly to me - whether an 056 piston will sit on a 660's connecting rod?

I'm also curious why I'm seeing 52mm all the way to 56mm for 056's....had always (wrongly)assumed it was some unrelated model but it seems it's "part-related" to the 066/660 line and I'm curious for all anyone is willing to share but most interested in whether the piston will fit a 660, because they (lil red barn) sells 56mm 056 pistons that are just beautifully domed and definitely have longer skirts than the big-bore 660 56mm pistons do (which is my setup right now on one of my units) and if I could just use the 56mm 056 piston - even if I've gotta do a lot of work ot it - if it just fits that connecting rod I'm set, I'm happy machining the crown and even going single-ringed I'm just not setup to alter the gudgeon/wristpin so it needs to be "plug&play" fitment to the 660 connecting rod!

Thanks a ton, the piston's most important but I actually am very curious about the 056, for isntance if I had 056 jugs - 52mm and 56mm ones - would both, either, neither of them fit a 660? To be crystal clear, I'm only talking about fit, not "will it work if I just drop it in?" yknow!
So, the Stihl 056 had several variants over the years. As I recall, the plain 056 was 52mm and about 81cc's, the 056 Super was 54mm and 87cc's, the 056 Mag II was 56mm and 93cc's. The 056 Mag II had bigger bolt spacings on the case since the bore was larger, and you'd have to slot out the bolt holes to get the jug to work on older cases. Even then, you may have to machine larger reliefs on the inside of the cases as well to allow for the larger piston. An 056 Mag II cylinder will bolt on an 066 case with a little bit of clearancing, and I believe the piston will work on the 066 crank provided you use the 056 pin bearing. Now, here's a warning. The two a/m 54mm pistons I got from the Duke (which are probably made by the same company as LRB's pistons) had too much slop in the con rod region. Instead of being 14mm they were about 17mm between the "ears". I had to make a set of thrust washers to use one of those in an 056. I don't know if the 56mm slugs have the same issue, but I'd check that as soon as they show up in case they're too wide as well.
 
So, the Stihl 056 had several variants over the years. As I recall, the plain 056 was 52mm and about 81cc's, the 056 Super was 54mm and 87cc's, the 056 Mag II was 56mm and 93cc's. The 056 Mag II had bigger bolt spacings on the case since the bore was larger, and you'd have to slot out the bolt holes to get the jug to work on older cases. Even then, you may have to machine larger reliefs on the inside of the cases as well to allow for the larger piston. An 056 Mag II cylinder will bolt on an 066 case with a little bit of clearancing, and I believe the piston will work on the 066 crank provided you use the 056 pin bearing. Now, here's a warning. The two a/m 54mm pistons I got from the Duke (which are probably made by the same company as LRB's pistons) had too much slop in the con rod region. Instead of being 14mm they were about 17mm between the "ears". I had to make a set of thrust washers to use one of those in an 056. I don't know if the 56mm slugs have the same issue, but I'd check that as soon as they show up in case they're too wide as well.
That took a couple reads but I think I do understand, if I have 660 cases (as I do) then most of the 056 stuff is no good except for the 056II 56mm? That's actually precisely what I was hoping for, because I've rebuilt one of my 660's with 56mm big-bore kit but I had to go through 3 kits ROFL to get it just right, and the biggest(only) problem is the stupid piston they make the skirts nearly 2mm(73thou) shorter than OEM, which seems silly to me because even at the 1.610" height they come at they do most definitely have their skirts going under the jug/into casing and the casing is way larger than 56mm there, not that that matters as I was getting my 1st kit expecting that I had to modify the case for fitment, was not happy/was upset finding cut skirts :/

It took 3 kits to finally get a build I like, but now you have me freaked-out about the slop between the 'ears' or "gudgeon pin bosses", I had (3) 56mm's choose from and the slop was, best to worse:
- Hyway (13.55mm), then
- Farmertec ( 14.5mm) and then
- "NewJ's" which, being installed, I cannot measure but I remember thinking the farmertec was "midway" between the two so am guessing about ~15mm.....it did really bother me but I pictured the piston moving in its vertical-axis plane of motion and, considering even 1mm of slop could have overhang of 1.0mm, I reasoned that it probably "aims for straightness" given the centrifugal force of the rod...

Darn now I'm all worried about this build, it's gone through heat cycling and break-in but has only done modest "extended length full-throttle" (in wood of course), will be taking the head off for piston check in several tanks will get to see then (love how easy it is working on these, I use the gaskets in a disposable fashion so I don't have to fight w/ Moto on that tiny mating surface, the 56mm jugs come with 54mm sized chambers and on the NewJ's one the exhaust floor was a good 60thou higher than OEM so it allowed me to drop it 10thou while still having 50 of before-freeport, got to flatten 1/3rd of the band and polish the rest at OEM-angle into that smaller chamber ;D

Would be curious Re "thrust washers" you used, sounds like you made them? Was close to going to Ace and just finding alum or steel washers but remembered Jennings & Blair both talking about different metals' expansion rates so I figured to just go with what I had...there's a good chance I'll swap over to the Hyway anyways, only reason I couldn't is because Hyway made it w/ the locator pin >3mm out of place so it'd let a ring into my upper transfer, am still kinda "back&forthing" with the (known) seller because I did accept & port it before I noticed the pin was outta place (sucks because I *did* check pin location, obviously as it's an involved build, but I must've just checked 1 side and it wasn't the outta place side!)
 

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