Pistons and the 066/660

[excess650]

I've been working on a Stihl MS660 "in a box", and have had the opportunity to compare, measure, and weigh pistons.

The OEM Mahle piston is pretty nice, relatively light, and could be further massaged to lighten and open the windows.

Meteor's offering is eye candy out of the box, but at the price of weight, as you'll see.

Bailey's big bore and replacement pistons both are of decent quality, and can be massaged to make them better.

I also have a GB piston for 272xp to compare. Its 2mm smaller than OEM 066/660, but I thought it worth comparing in a relative sense. Its not as pretty to look at in that its not bright and shiny, but very lightweight, and without a lot of flashing or sharp edges.

Both the GB and Meteor pistons have the windows wide open, with more sharp edges and flashing on the Meteor.

The Stihl and Bailey's pistons could be enhanced by opening the windows to reduce weight, and enhance flow.

Weights as supplied:

Stihl OEM Mahle 89g
Bailey's replacement 89g as massaged 87g
Meteor replacement 97g
Bailey's Big Bore 56mm 97g as massaged 94g
**GB 52mm 272xp piston**78g

Stihl's supplied wristpin was thinner than the others and at 14g some 4g lighter than the others.

Overall height was similar between Stihl, Bailey's replacement, and Meteor replacement at 1.695" Bailey's BB was some .080" shorter on the skirt.

Both of Bailey's pistons have a shorter height from center of rod to top of crown. The replacement piston was .005" shorter than OEM and Meteor while the BB was .012". Naturally, the Bailey's replacement will yield less compression in the OEM cylinder.

I checked squish with OEM P&C, Bailey's BB, and OEM cylinder with Bailey's replacement piston without gaskets.

OEM .015"
Bailey's replacement .020"
Bailey's BB .010" *** the BB cylinder is bored to a shallower depth to squish band than the 2 OEM cylinders that I had to checK!***

minimum distance from crown to window opening:

Stihl .415"
Bailey's BB .440"
Meteor .450"
*couldn't compare GB as its a single ring design, and the Bailey's repalcement is already buttoned up in my 660*

As previously mentioned, the Meteor and GB windows are nearly wide open with the exception of flashing. There is a bit of meat to be removed from the Stihl and Bailey's to open them up.

The real surprise is the fact that the Meteor 54mm is as heavy as the Bailey's BB 56mm as delivered. Both can be massaged to lighten, but I doubt the Meteor will be lighter than the BB when finished without a lot of work. I'm wishing that I had a GB 54mm 066 piston to compare for more of "apples to apples".

My choice for piston pin would be the Stihl, regardless of piston.

If I can, I'll post some pictures later.

 

[timberwolf]

There is quite a difference too between the original 066 stihl piston and the 660 piston. Strongly suspect the alloy is even different.

 

[excess650]

Piston pictures:

http://s236.photobucket.com/albums/...insaw stuff/?action=view&current=IMG_0148.jpg

http://s236.photobucket.com/albums/...insaw stuff/?action=view&current=IMG_0149.jpg

http://s236.photobucket.com/albums/...insaw stuff/?action=view&current=IMG_0150.jpg

http://s236.photobucket.com/albums/...insaw stuff/?action=view&current=IMG_0151.jpg

I tired to crop and adjust contrast, but I suspect the differences are more visible in-hand as opposed to the pictures.

 

[blsnelling]

Excellent info here. It's easy to see why the Meteor piston is heavier. Look at the meat in the skirt support and the thickness of the skirts themselves. That's one beefy piston. If you want it lighter, there's a lot there to work with. I think I'll go order one for my 064

 

[sILlogger]

Excellent info here. It's easy to see why the Meteor piston is heavier. Look at the meat in the skirt support and the thickness of the skirts themselves. That's one beefy piston. If you want it lighter, there's a lot there to work with. I think I'll go order one for my 064

I was quite impressed with meteors pistons. good fit and finish and seem to be good quality. but they are definitely built heavy....although that is becoming less and less of a problem as fewer and fewer of my saws are stock!!

i've got a meteor in an 066

 

[blsnelling]

I just ordered one for the 064 this afternoon.

 

[redunshee]

066 and GB piston

Anyone have any experience or comments on the GB aftermarket piston for the 066. Have my eyes on an 066 with a GB piston. Wonder how they hold up.
Bob