Piston clearance

[mountainlake]

What should the piston skirt to cylinder clearance be on a 028 WB 44mm cylinder, it's about .007 thousands . It had a lot of blow back through the carb and rather gutless, the piston, cylinder and rings all look real good. It has a domed piston, will a flat top work. Also has a real thick base gasket, do they make thinner ones. Steve

 

[kr5258]

As far as I know, the standard base gasket was 0.5mm. I also thought that the domed piston came on the Super 46mm cylinder, flat tops came with the 44mm cylinder.

Still, .007 at the skirt seems excessive to me.

 

[mountainlake]

Thanks. I'll have to check the domed part, had 2 different saws apart and may have gotten mixed up. Sounds like time for a metour piston. Steve

 

[chip4664]

.0035" is where I like to be on a rebuild on an air cooled motor with a cast piston. You may get some slap at .007"

 

[tomdcoker]

As far as I know, the standard base gasket was 0.5mm. I also thought that the domed piston came on the Super 46mm cylinder, flat tops came with the 44mm cylinder.

Still, .007 at the skirt seems excessive to me.

I have had two 028 supers, the first one had a domed piston the current one does not. I was going to ask on here about this and have not got arround to asking.
The current one is a Stihl 028 wood boss super with the letters super in red. I cannot remember about the first one. I just kow it was a super. Tom

 

[kr5258]

I don't have a Super with red lettering so I wonder....
So I go to my pile O' 028s and start pulling plugs....
4 domed pistons (Supers) and 1 flat top (Wood Boss).
Have you had the red lettered Super since new? I wonder if the piston was swapped out at some point or if the red Supers came that way.
Anybody else out there with a red lettered Super that can check theirs?

 

[tomdcoker]

I don't have a Super with red lettering so I wonder....
So I go to my pile O' 028s and start pulling plugs....
4 domed pistons (Supers) and 1 flat top (Wood Boss).
Have you had the red lettered Super since new? I wonder if the piston was swapped out at some point or if the red Supers came that way.
Anybody else out there with a red lettered Super that can check theirs?

I bought the saw recently from the estate of a Doctor. I believe it to be orignal. It has very little paint loss or other signs of use.
It is a used saw and I do not know the history so it is possable that it is not orignal. Tom

 

[mountainlake]

.0035" is where I like to be on a rebuild on an air cooled motor with a cast piston. You may get some slap at .007"

Not only piston slap but the skirt has to seal the intake port on the down stroke, too much clearance = excessive blow back through the carb. Steve

 

[Mad Professor]

new oem will be 0.0025-0.003

0.007 is getting sloppy/slappy