Squish dilemma/Porting opinion

[drf255]

So I'm playing with an ms260 jug. After the band and base cut, I wound up with a squish of .017 using .033 solder. I rechecked with .023 solder, and the measurement went down to .013-.014!!!

Using the smallest solder closest to your expected dimension does make a difference.

I was able to get the exhaust roof down to 102.5* with an .054 square band cut.

So the question is this. I'm freeporting under the skirt on the exhaust side about .005. I need to open squish up to .017-.018.

Would you add a metal base gasket to increase squish (will reduce both freeporting and exhaust degrees) or would you sand another .004 out of the band?

 

[stihlbro]

Are you Checking squish in at least two spots at the same time? Is the ring in the piston? I prefer to measure in the 12,3,6 and 9 o'clock positions with lead held to the top of piston with a grease, measure all 4 locations.

.005 freeporting at idle, say 2800 rpm I doubt you would notice it.

Recheck squish in 4 spots, post up what you have.


Joey

 

[drf255]

Was 4 spots. No starter cord. Turning flywheel by hand. No ring on.






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[stihlbro]

I prefer base gaskets, but that is just me.


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[jmssaws]

I always use a gasket, sealor is messy.
A 005 Freeport is nothing I'd worry about at all.

053 from the chamber should make a runner, I'd raise the exhaust though.

 

[Ironworker]

I would just add the gasket.

 

[drf255]

A gasket will raise the exhaust. I'm trying to go with an exhaust vs. displacement rule of a 105* goal for a 50cc saw.

Hard as hell to get there with a Stihl 026. Even with a red lever jug, I could just get 103.5 with a .050+ SB cut

 

[Mattyo]

Now I feel really bad doc.... your port work is way nicer than mine .... and the 350 still won hehehehheehhehehe

 

[redfin]

Where is your intake and transfers as it sits now?

 

[stihlbro]

102 ish is a good number for the exhaust in my opinion. Especially on a 260.


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[Canadian farm boy]

I'd make a gasket and use a touch of sealant. I believe a brown paper bag measures around .004-.005.

 

[jmssaws]

I agree with 102-101 depending on transfer height.

What's the compression?

 

[drf255]

Now I feel really bad doc.... your port work is way nicer than mine .... and the 350 still won hehehehheehhehehe

Not this one Matty. Although it's tough to beat a quad w a dual.

I agree with 102-101 depending on transfer height.

What's the compression?

Not assembled yet.

 

[jmssaws]

I've never tried bridges in a saw that small, curious for sure.

 

[jmssaws]

Not this one Matty. Although it's tough to beat a quad w a dual.

I disagree with that completely.

 

[Mattyo]

We will see doc....we will see.

 

[stihlbro]

Do the bridges work?


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[jmssaws]

I'm curious on that small cc if bridges work, it's about redirecting flow so I bet fingers do.

 

[SquareFile]

Do the bridges work?


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[Paragon Builder]

I think you will be just fine with the small amount of free porting.
In fact since it's a 50 cc saw (small) I'd run it as is and see how it runs. That way if you decide the free porting is an issue you can pop a gasket in. If you cut the squish band more you will be too big if you need to add a gasket.
I found the same thing checking for squish. So i use very small solder and twist it to get big enough. It crushes much better in my opinion.



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