MS250-Too Much Compression?

[drf255]

Do I run a huge risk if I just put some fuel in the intake boot?

Think I'm wimping out and dissembling it.

 

[wigglesworth]

Do I run a huge risk if I just put some fuel in the intake boot?

Think I'm wimping out and dissembling it.

Do what makes u comfortable.

And that's a big no on firing it off with no carb. She'll sing to the moon!!

 

[nmurph]

...and you're not losing 30-40psi from cold to hot. It's more like 10-15psi.


I doubt he timed it if he's asking about "taking 1-2mm" of the exhaust to reduce compression (yes, that will reduce compression...).

 

[c5rulz]

Fire that bad boy up, I wanna see how this turns out. It's not like you are going to be out a "good" saw.

 

[drf255]

It's coming apart. This is my 3rd 025/250 rebuild. Got it down to the tank and motor in under a half hour.

I Dirko'd the hell out of it. Even around the seals. The cleanups gonna be a beoch.

It's a "good saw" to me. I want performance, but also something that lasts.

I'm gonna try to get it down to the 180-200 psi range.

The ports have been played with already, just squared, enlarged and blended. I didn't mess with the timing.

This time I'm testing compression BEFORE I glue the engine back together.

For those who wanted to see it explode, sorry.






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[Deleted member 83629]

good luck.

 

[drf255]

It's out




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[drf255]

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[NewToStihl]

It's out

View attachment 389774

You said you "Dirko'd the hell out of it". I'm not trying to split hairs, just curious; All of the Dirko I've ever seen is red & your sealant looks grey. Is it actually Dirko, or something similar?

 

[drf255]

It's dirko. The one I bought grey.

 

[NewToStihl]

It's dirko. The one I bought grey.

That's interesting, I wonder if there's a difference between them?

 

[blsnelling]

This time I'm testing compression BEFORE I glue the engine back together.

You will not get an accurate compression test until it has been run to clean the assembly lube out of it.

 

[blsnelling]

The ports have been played with already, just squared, enlarged and blended. I didn't mess with the timing.

You're missing a very critical part. Until you degree that cylinder, and put the port timing where it should be, you're leaving a huge piece of the pie out of the equation. The transfers likely need raise, and the intake probably needs lowered. You will see gains for your port widening, but not what it could be. You can print out a paper degree wheel, sized to the diameter of your flywheel, and then simply glue it onto the fins. Make sure it's centered and that will be plenty good enough. Let us know what your stock port timing is and we can go from there.

 

[drf255]

You're missing a very critical part. Until you degree that cylinder, and put the port timing where it should be, you're leaving a huge piece of the pie out of the equation. The transfers likely need raise, and the intake probably needs lowered. You will see gains for your port widening, but not what it could be. You can print out a paper degree wheel, sized to the diameter of your flywheel, and then simply glue it onto the fins. Make sure it's centered and that will be plenty good enough. Let us know what your stock port timing is and we can go from there.

I don't have the knowledge you do Brad. I figured I'd worsen whatever the engineers calculated more than I'd help.

It's also a clamshell with very long and thin transfer ports. Not the typical ones with an entry and exit.

I'm reading Jennings books now. I have a 12" automotive degree wheel. I need to make an adapter.

I do sincerely appreciate all the advice you've given.

 

[blsnelling]

Just glue a degree wheel onto the flywheel. There's no need to go to the trouble to make an adapter unless you plan on doing more saws.

 

[drf255]

Reduced dome.

Gonna rebevel ports.

Keep ring gaps at .008 or open a bit?


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[drf255]

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[blsnelling]

Leave the rings as they are.

 

[drf255]

Thanks. I rechamfered my ports.

Sanded piston from what you saw above. Blended any hot spots.

With an oiled cylinder, I'm at 210 psi now.

 

[AKDoug]

Fire it up