Saw mods

[Lawn Masters]

Just a question, what all does a saw builder modify to get the very most from a saw? I know the mufflers are a big thing in this as are the transfer ports, but what else all is modified?

My reason for asking this is that I would like to have a better understanding of how a modified saw works. If one understands the saw better, then one can potentially think about it and come up with ways to actually get more from the saw.

 

[Grande Dog]

One thing that I like to do with the Husky 372 is to get rid of the cylinder gasket and reassemble using Loctite # 518 gasket eiliminator. You'll lose about 1cc in displacement but the change in compression will boost the power. Best of all no special tools.

Grande Dog
Master Mechanic
Discount Arborist Equipment and Tree Care Supplies

 

[Crofter]

Originally posted by Grande Dog
One thing that I like to do with the Husky 372 is to get rid of the cylinder gasket and reassemble using Loctite # 518 gasket eiliminator. You'll lose about 1cc in displacement but the change in compression will boost the power. Best of all no special tools.

Where do you "lose" the displacement to?

Frank

 

[066 stihl]

Crofter

You would lose cc's in the combustion chamber. That's how you gain more compression.

Ricky

 

[cbfarmall]

But you don't lose displacement. Stroke is the same, and the bore doesn't change.

Chris B.

 

[ehp]

But you missed the biggest thing by taking your base gasketsout , you change your port timing , I know most guys think that just that .025 gasket would not change much but it does ,yes you need compression but the more compression you have the hotter your saw is going to run , this is ok for ******** but not good for a woodsaw,
Frank I already knew you had that figured out.
saw builders here will mod. your intake, ext. and transfer ports plus get your compression to the numbers he wants,

 

[Crofter]

066 Stihl. i agree with the increase in compression. Displacement (nominal) is a factor of stroke multiplied by area of the bore and is not affected by moving the jug up or down. Effective displacement is the distance travelled after the exhaust port is covered thence to the end of the stroke, multiplied by the bore area. Since lowering the jug the gasket thickness would cover the port sooner, I am sure effective DISPLACEMENT is slightly GREATER and since final compressed volume is SMALLER, compression is indeed higher. The exhaust and intake timing events will have been changed though and torque and horsepower peaks will likely happen at a lower RPM.

Frank

 

[ehp]

Frank you are our winner. yes the engine will pull at a lower rpm.

 

[Crofter]

Ehp; I can tell by the saws you built me that you did just a smidge more than throw the gaskets away! I haven't taken them apart yet to discover your secrets. I usually have a pretty inquisitive nature, but for that I will take your word.
There is one bad thing about saw modifications though! Once you have felt the differenc there is no looking back!

Frank

 

[rbtree]

Ain't that the truth!!!

Rog the saw junkie

 

[heffayinthebush]

Hey chainsaw dudes, this subject has me entrigued. Recently we blew up our Walkerized 357, and dicovered only the top on the port side of the piston broke. A chunk above the ring about a centimeter log cracked off and landed in the muffler.

After we took it apart, the cylinder wasn't damaged (thanfully) so we just ordered a new top end kit and reassembled.

But I'm puzzled, after examining the cylinder thoroughly, I can't figure out where the walkerizing has been done. None of the ports appear to be raised, doesn't look like the base has been lowered (machined). What do they do besides mod the muffler?

Heff
firewood.ca

 

[glens]

I recall Jacob J. talking about them doing a bit of work to the piston itself.  If I both understood and recollect that right, it sounds like you'll be reverting to a more stock configuration again.

I guess I had in mind something like the second to last <b>post</b> listed <a href="http://www.arboristsite.com/search.php?s=&action=showresults&searchid=204783&sortby=lastpost&sortorder=descending">here</a>.

Glen

 

[ehp]

Crpfter there was a little more machining that when on in your 260 than the base gasket, you should of felt your saw is 1 pound lighter now, and i think it will get stronger yet

 

[Jacob J.]

One thing you're going to find out, and find out fast, is that if you live in an area where they put more ethanol or equivalent alcohol type additives in your gas, you're going to want that extra room in the combustion chamber for expansion of the flame front after combustion.

I've gotten more power out of later model saws by using base gaskets but increasing the combustion chamber volume by beveling the top of the piston. This also gives the charge more surface area on which to push the piston down after firing.

 

[Crofter]

Originally posted by Jacob J.
.

beveling the top of the piston. This also gives the charge more surface area on which to push the piston down after firing.

Removing metal around edges of piston will alter port timing and would relieve a too small squish situation, but I question the explanation of increased surface area harnessing more of the charges potential power. EFFECTIVE frontal area of a piston is not influenced by its surface area but only simple diameter.

Your point is valid tho about different fuels possibly being a problem. When you modify a saw lots of interactions can start to happen that can stack up and create a disaster. You better trust your buider!

Frank

 

[bwalker]

you're going to want that extra room in the combustion chamber for expansion of the flame front after combustion.

Please explain, Jacob.

 

[geofore]

no looking back

I told RAH, the first time I met him, that modded saws were great and you know what happened to him. Now Rich has more modded saws than he can hide from his wife and the itch to get more saws. Once you've tried one you have to have two and there is no going back. Is it worth the money to get them modded? Yes I have fun with mine.