Variation in Squish?

[blsnelling]

https://mahle.partnumber.company/mpy-1-yellow-plastigage-plastiguage-plastigauge-clevite

If I'm reading right, that only goes up to .020". His squish is greater than that on two corners.

 

[mdavlee]

It's actually around .030-035" if measured before being mashed.

 

[Al Smith]

Well that wouldn't do you a whole lot of good .You flatten that stuff out and use the chart on the folder to get the measurements not peel off and use a set of micrometers like solder .

 

[Al Smith]

We've got all kinds of shim stock.steel,brass,aluminum and plastic .It comes on various thicknesses .I had thought about using plastic which is in .002" increments and just "feel" when it hits the top but after thinking about it solder would be a whole lot more simple .It's a chainsaw not a part for the space shuttle .

 

[Moparmyway]

Well that wouldn't do you a whole lot of good .You flatten that stuff out and use the chart on the folder to get the measurements not peel off and use a set of micrometers like solder .

Its just another way to skin the cat.
Pull the gasket and measure with the yellow, then just add the gasket thickness for total squish

 

[JonCraig]

I was planning on just motoseal. Does that add any measurable thickness? Or just seal imperfections in the two surfaces?

 

[Al Smith]

Pull the gasket and measure with the yellow, then just add the gasket thickness for total squish

Never thought of that but even with 20 thou gasket thickness for Stihl it would not be enough for many .Seems to me like the 038 mag was around 46 thou stock .The 200T was around 35 I think . I took them both to around 23 if I recall .The two 038's and the 200 are the only ones I've cut down .Nothing on the Husqvarnas and nothing you can do to the McCullochs regarding that .

 

[blsnelling]

Most Stihl cylinder gaskets are .017".

 

[Al Smith]

Not with a set of Starrett micrometers .

 

[Moparmyway]

Never thought of that but even with 20 thou gasket thickness for Stihl it would not be enough for many .Seems to me like the 038 mag was around 46 thou stock .The 200T was around 35 I think . I took them both to around 23 if I recall .The two 038's and the 200 are the only ones I've cut down .Nothing on the Husqvarnas and nothing you can do to the McCullochs regarding that .

Al, the yellow plastigauge isnt a cure for everyone or everything.
Its just another option.
Causes guys to think about skinning the cat.

Wasnt the origional suggestion of using yellow plastigauge for the origional problem with the offset cylinder in question ?

I dont have any problems using it on any make/model saw that isnt a clamshell.

I've got several different ways to measure squish, as does everyone else. Its just a matter of options and perspective

 

[mdavlee]

Well that wouldn't do you a whole lot of good .You flatten that stuff out and use the chart on the folder to get the measurements not peel off and use a set of micrometers like solder .

Correct. If it does read above .020" then solder will read about the same. .023" solder wouk d read .018-020". Plastigauge was reading .011-012". 372 run like that for a tank or two before I pulled it apart to change something. Then I checked it again with plastigauge and figured that out.

 

[drf256]

Solder measures larger than true. The further away the parent compound from the intended sqush and the less amount of times it’s compressed leads to a bad read.

Anyone that does machining here knows this to be true. Have stock squish of 32 without gasket. Take 30 from band and wind up at 62 squish now-mathematically. Check squish again with thicker solder-it’s 66-maybe. May I didn’t take what I thought?

OK, if I take 46 from the band, I’ll be at a perfect 20 squish. Take 46, measure, and you get .008.

I go with a goal of 18, then I sand the final amount from the band. How much a squish .005 larger is gonna make a saw run? Would have to do a side by side on a dyno.

 

[drf256]

Most Stihl cylinder gaskets are .017".

Not true. Maybe most models you’ve worked on.

026 and 260 44mm are about .009. The 44.7 is around .017.

I just measured a 460 D jug which was .027 sans gasket. 1128 series are the worst in terms of variation.

On a few models I do frequently, I've resorted to using a depth mic to measure final base to band amount at a given squish. Case variation occurs, but it gets me in the ballpark.

 

[Al Smith]

This much I do know .If you cut down the cylinder make certain you mark one cylinder flange to measure from because there are some variances .Then if you cut too much off you have get creative in making a new gasket .Just for general info the cardboard from a case of Bud Light it exactly 25 thou measured with a set of Starrett carbide tipped micrometers . Which by the way measures 25.5 thou with a set of Mitutoyo verniers.I know the Starrett is dead azz on the money not that a half a thou means that much .