Squish... Should I care?

[Simondo]

Gentleman.
Iv not got as far as gasket deletes or changing the compression of my saws . Have looked over many bits of info on this but not taken the plunge and stuck to ins and outs + muffler mods..so I'm wondering.
If you can tighten up the top end clearance to get more compression at the top of the stroke , then you would change the port timming if you made no further compensations.
Is this ok…or is it a must to change the top of port hight inside the cylinder or "Deck" the base ..Always ?
Please excuse me if this has been well covered in the past.
Thanks
Simon

 

[Mastermind]

The timing changes are slight enough to not be of any concern.

 

[Backyard Lumberjack]

100% true.

I just did Backtroller's 034 to ported 036 conversion, and my MS360 building case had a .005 variation in squish from Pat's saw. .015 vs. .020 on my case.

Attention to detail separates the men from the boys in this rodeo.[/QUOTE]

again, at the risk of sounding redundant... 100% true. (as in gospel) take it to the bank sort of thing...

my father was a skilled gun smith (award winning) and an excellent, competent mechanic... full A & P Certification, among other things in his career path. one thing he always said about engine building: " cleanliness is next to Godliness! " and cleanliness is in the details...

guess I would get to greasy helping him at age 5.... lol

 

[Backyard Lumberjack]

The timing changes are slight enough to not be of any concern.

and I read, I believe it was in one of my favorite porter's comments... Mr. MM... these base of cyl changes and squish modes, cut or gasket induced... while moving the port timing some, won't be materially affected if kept within 020-040 range. one only has to hunt up suggested port timing numbers and its clear no two suggestions are the same. these principles helped guide me in setting my port cleanup limits and base gasket mods as I measured my squish changes and extrapolated them to changes in piston to port location relationships.

"well, that's my story and I am stickin' to it!"...

 

[Simondo]

The timing changes are slight enough to not be of any concern.

And the gain "Usually" outstrips the slight changes in timing i take it ?

 

[wildroamer]

Excellent information gang, this place ROCKS!
I will indeed be taking much of the advice offered, thanks!
Won't be going as far as some of you, piston - cyl wall clearance, vacuum testing, etc. But will post a new thread when I finally get going on this.
Cheers all, Happy Hump Day Eve!

 

[Mag Craft]

If you are going to be working on saws for any length of time learn how and get the tools to check the squish. It is probably as easy as doing a compression test and it will give you some very good information. If your deleting bases gaskets and swapping cylinders around you need to check the squish.

What if you bought a new saw from one of these shady saw builders that I have seen around and something did not seem right. Well checking the squish is just one more tool to find out what is going on.

 

[Backyard Lumberjack]

If you are going to be working on saws for any length of time learn how and get the tools to check the squish. It is probably as easy as doing a compression test and it will give you some very good information. If your deleting bases gaskets and swapping cylinders around you need to check the squish.

What if you bought a new saw from one of these shady saw builders that I have seen around and something did not seem right. Well checking the squish is just one more tool to find out what is going on.

right on! there Mag Craft! at 13,500 rpms, 225 piston cycles per second, 600 chain teeth passing a single point per second... at about 70 mph...

you gotta know what's going one. to paraphrase one popular social comment: "squish matters!'

lol

 

[concretegrazer]

Hi gang,

Getting ahead of myself, but thinking about the Solo 681 P/C kit on the 665. If my plan is simply a swap, no porting, do you guys think I need to worry about measuring squish?

I know it is not an enormous undertaking, but it would require me to buy a few things, calipers, solder, etc. I'm just wondering if I really need to bother. It seems that slapping the gasket that came with the kit on, bolting the sucker up, and running it would be fine.

Thoughts? As a novice, I am thinking that the only reason I would be concerned with squish is if I was contemplating a gasket-less install, in an attempt to squeeze the most power from the saw.

What am I missing?

@DexterDay did a good thread on FHC on the 665 to 681 conversion. It looked fairly simple. I can find it if you'd like.

 

[wildroamer]

Thanks, I have seen it and it is the main reason I thought I would try to tackle this!

 

[mdavlee]

There's more than likely going to be .025-030" with a gasket on those. Stihl is the only manufacturer I've seen a saw under .020" from the factory. I'd check it just to check it and maybe you can delete the gasket. .017" or whatever the gasket is will be 1.5 degrees or a little less. Nothing you can notice more than likely

 

[wildroamer]

Maybe I should start a raffle or something. "Guess my squish!"

 

[angelo c]

Maybe I should start a raffle or something. "Guess my squish!"

well at least that's better then the last raffle I won... "who wants to touch my squish..." ???

 

[David Young]

probably common knowledge but...

make sure it is lead solder other varieties are harder and don't squish easy.

 

[wildroamer]

well at least that's better then the last raffle I won... "who wants to touch my squish..." ???

 

[wildroamer]

Thanks for the head's up, DY. I did read that I should be looking for a rosin core solder.

 

[Marshy]

They make different diameters too. You shouldn't need anything over .050 but idk what increment they actually sell the stuff in.

 

[wildroamer]

Yup, I see Radio Shack has .032. Of course I feel a bit silly dropping $15 for an 8 oz roll when I need, what, 2" lol?

 

[mdavlee]

Use .032" if you can find it. The thicker it is the more it can show a bigger reading. Under .018" the .032" stuff reads bigger than the actual gap.

 

[Marshy]

Yup, I see Radio Shack has .032. Of course I feel a bit silly dropping $15 for an 8 oz roll when I need, what, 2" lol?

You'll need more for your second saw.