Chainsaw Repair

Probably safer to flip the piston with the oem pin location as widening the transfers will aggravate the tendency to catch the transfer port.

What advantages was there in running the stihl 046 piston over the husky 272 piston in the 7900?  Care to share info?

Sounds good.  Thanks.

I've built em with the 272 piston which is taller and requires a bigger spacer plate under the cylinder.  This increases volume and lowers the crankcase pressure, slowing the flow . The  046 piston can be installed with .058 or so gasket and keeps the volume closer to stock.

So basically when you monkey with one aspect of a saw, like crankcase volume it can adversely affect the whole dynamic.   Make the ports too big and flow is reduced, when flow is reduced you need more duration, and on, and on, an on!!!!! Lol!!!

Did you pick up one of those wide skirt wiseco pistons Ed Heard EHP had made up for the 5 cube saws?  Some folks were getting them to put in so called woods ports for gtg racesaws too.   

Wish info on the 046 was there for comparison too.

Per EHP = piston on left is a 7900 used piston, with ring it weighs 85.4 grams , skirt width of 32mm/ 1.260 inch
middle is the wide skirt wiseco piston, with ring it weighs 79.7 grams and has a skirt width of 1.670 /42,5mm
right piston is a stock 272 piston weight was 82.9 grams with ring , skirt width is 35.83mm/1.414 inch,
so race piston is wider and lighter and will fit the 7900/272/460 stihl , I built this piston maining for a race piston and to be run on alcohol/nitro, as you can see its coated everywhere
the 52mm pistons are to be used on a nikasil bore, not chrome bore as Wiseco does not make a 52mm ring to run on chrome bore  , you also have to use the pin from the stihl 460 as that is the pin I had the c-clip groove set at

The 272 piston looks like the best bang for the buck option.  You could push the port out to around 67% of the bore width.