High Quality Chainsaw Bars Husqvarna Toys

Part One: The Exhaust Port

Fairways_and_Greens

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Using what Andre was doing on the 346XP that beat all of our asses at Wigg's GTG several years ago........and the heights of some of my stronger running 90cc saws, I arrived at a EX height to CC scale sorta thing.

Now......there are exceptions, so remember this ain't "the gospel". lol

50cc - 105°
60cc - 103°
70cc - 101°
90cc - 100°
120cc - 98°

The biggest exceptions to this "rule" for me are the stroker or over square type engines. They get "different".

Would that put an MS241 at about 106° or 107° Randy?
 

Fairways_and_Greens

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So in taking @Mastermind 's video in setting up a homemade wheel attached to flywheel, I came up with something like this:
IMG_0163.jpg

Going up to 106° get's me to .735 to the squish.
IMG_0165.jpg

So according to the rule of thumb of 65% to 70% of the 1.67 inch piston, I can cut up to that cardboard and 1.085" - 1.169" wide?


Last question: does just blending to to the exhaust gasket size look good or do I need to go wider?
IMG_0164.jpg
 

Deets066

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So in taking @Mastermind 's video in setting up a homemade wheel attached to flywheel, I came up with something like this:
View attachment 158127

Going up to 106° get's me to .735 to the squish.
View attachment 158129

So according to the rule of thumb of 65% to 70% of the 1.67 inch piston, I can cut up to that cardboard and 1.085" - 1.169" wide?


Last question: does just blending to to the exhaust gasket size look good or do I need to go wider?
View attachment 158128
You sure you measured right?
If you raise your port up to that cardboard, I find it hard to believe your gunna be at 106
 

XP_Slinger

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When you say flange, are you referring to the piston? It seems like I have room for days there.
View attachment 158204
He meant the muffler mounting flange. If you widen the exhaust to 70%, you will want to widen the entire port to the same width all the way out to the flange.

Piston skirt width is another consideration when widening the exhaust. But as you said, it looks like you’ve got plenty of room there.
 

Fairways_and_Greens

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He meant the muffler mounting flange. If you widen the exhaust to 70%, you will want to widen the entire port to the same width all the way out to the flange.

Piston skirt width is another consideration when widening the exhaust. But as you said, it looks like you’ve got plenty of room there.

Interesting Slinger, you got me thinking, so I tried my best to trace out the current configuration. I didn't do a great job with scissors (bad sign).

Right now the cylinder side of the port is a touch wider than muffler side. Also, the area between the two appears to be at a ratio of 2:1. Is that a good rule of thumb to maintain?

Do you recommend keeping the widths the same throughout the port Slinger?
IMG_0170.jpg
 

Fairways_and_Greens

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I'm talking about thru the outlet in the jug. Widen it too much, and you cut a hole.....

I see what you're saying now Randy, looking at the port casting from underneath. Thanks for slowing me down and leaving me bread crumbs.

Regarding the flange. My thought was to just match the muffler gasket.
IMG_0168.jpg IMG_0169.jpg
 

XP_Slinger

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Interesting Slinger, you got me thinking, so I tried my best to trace out the current configuration. I didn't do a great job with scissors (bad sign).

Right now the cylinder side of the port is a touch wider than muffler side. Also, the area between the two appears to be at a ratio of 2:1. Is that a good rule of thumb to maintain?

Do you recommend keeping the widths the same throughout the port Slinger?
View attachment 158259
Yes that’s what I like to do. That’s why I don’t always go right to 70% of bore for width. I don’t see the point in widening the port window that far if there will be obstructions on the sides. But I’m still learning too bud, so please don’t take what I say as gospel.
 

Fairways_and_Greens

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Yes that’s what I like to do. That’s why I don’t always go right to 70% of bore for width. I don’t see the point in widening the port window that far if there will be obstructions on the sides. But I’m still learning too bud, so please don’t take what I say as gospel.

Hey Slinger. I'm like a blind man in an orgy right now. I appreciate the help. You're getting me to think about stuff I wasn't previously.

I think I'm going to try what Randy said re: look at that the saw designer did and go from there, so I think I'm going to try to retain the shape/ratio while creeping up to the timing.

I think I have a plan and am just delaying at this point. Worst case is I screw up the saw and send it to a professional!
 

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