Stihl 025, ms230 piston skirt difference

[Pioneer]

Noticed this when I pulled a Stihl 025 apart, it has a 30 thou relief on the intake side of the skirt compared to the ms230 piston. Means more intake duration, something to keep in mind as a reference if you are using an aftermarket piston to refresh your 025/250. I've seen some AM pistons that look like the relief is squared off instead of using a radius.

 

[ballisticdoughnut]

Hmm. Wonder if the MS250 piston is the same?

 

[pioneerguy600]

Noticed this when I pulled a Stihl 025 apart, it has a 30 thou relief on the intake side of the skirt compared to the ms230 piston. Means more intake duration, something to keep in mind as a reference if you are using an aftermarket piston to refresh your 025/250. I've seen some AM pistons that look like the relief is squared off instead of using a radius.

View attachment 1124651

Raising/shortening the piston skirt on the intake side and notching the piston crown at the upper transfers was some of the earliest porting tricks I was taught back in the 60`s, I am sort of surprised it is still being used on more modern saws

 

[thompsoncustom]

Raising/shortening the piston skirt on the intake side and notching the piston crown at the upper transfers was some of the earliest porting tricks I was taught back in the 60`s, I am sort of surprised it is still being used on more modern saws

As the old saying goes there's plenty of ways to skin a cat. Something I've wanted to try just haven't got around to it is to braze a big pop up piston on a clam shell. I even have the perfect donor sitting here just got to find the time.

 

[farmguywithasaw]

Raising/shortening the piston skirt on the intake side and notching the piston crown at the upper transfers was some of the earliest porting tricks I was taught back in the 60`s, I am sort of surprised it is still being used on more modern saws

If it works it works. The infernal combustion engine is over 100 years old

 

[pioneerguy600]

If I were controlling the cylinder casting process the ports would be positioned correctly for timing and then keep the piston skirt even all around, the intake side of the piston wears the quickest so a complete skirt would give the piston more thrust face support. In most saws the intake port can be lowered if necessary for more intake timing, in others it has been deemed to need raising just for modification sake to make more power, in stock form most saws run satisfactorily for the masses.