Jiles
Well-Known OPE Member
- Local time
- 9:56 AM
- User ID
- 2622
- Joined
- Feb 11, 2017
- Messages
- 24
- Reaction score
- 43
- Location
- Florence Alabama
I am a retired Tool&Die Maker.
Only time I mike Piston and cylinder is when mixing the items or replacing one with new or used. Taking measurements within .0005 is questionable. Any item can be cheated with measurement much more then .0005.
I always rely on piston ring gap to determine proper fit.
As has been stated, better to have too much gap then not enough and I am in agreement that .015 is acceptable and I have had no problems with .020-025 gap.
I build a lot of Stihl 200T and I check compression on a runnable engine before teardown.
On a used engine, compression might check to have 150 PSI compression with .020 ring gap checked after teardown. I always install new rings on these saws.
With a new set of OEM or Caber rings, gap would be .012 and after assembly, compression would be about five pounds more.
If piston is questionable, I use a smoothe style or worn file and file the piston in a circular manner. By this I mean, lightly file around piston (like painting)
Afterwards, I clean entire piston diameter with scotchbrite and WD40.
Only time I mike Piston and cylinder is when mixing the items or replacing one with new or used. Taking measurements within .0005 is questionable. Any item can be cheated with measurement much more then .0005.
I always rely on piston ring gap to determine proper fit.
As has been stated, better to have too much gap then not enough and I am in agreement that .015 is acceptable and I have had no problems with .020-025 gap.
I build a lot of Stihl 200T and I check compression on a runnable engine before teardown.
On a used engine, compression might check to have 150 PSI compression with .020 ring gap checked after teardown. I always install new rings on these saws.
With a new set of OEM or Caber rings, gap would be .012 and after assembly, compression would be about five pounds more.
If piston is questionable, I use a smoothe style or worn file and file the piston in a circular manner. By this I mean, lightly file around piston (like painting)
Afterwards, I clean entire piston diameter with scotchbrite and WD40.
