066.....What happened?

[Adirondackstihl]

Scoring on the intake side mainly.
Running VP SEF 32:1 with 800 2T.

I upon disassembly I found something interesting. The deco valve could barely stay closed with gravity alone.
Would this cause a lean condition? If you say yes, please explain your answer.

Exhaust side


Intake

 

[Adirondackstihl]

BTW, this is a very low hour 066 flat top.

 

[mdavlee]

Leaking decomps have caused scoring on one saw I picked up to rebuild. It's a quick fix usually. If they won't hold themselves up then it can suck air.

 

[nk14zp]

Any leaks around your filter letting dirt in?

 

[Adirondackstihl]

Leaking decomps have caused scoring on one saw I picked up to rebuild. It's a quick fix usually. If they won't hold themselves up then it can suck air.

I agree.
But there is something that bothers me about that theory!

At what point is the combustion chamber under vacuum ?

 

[mdavlee]

I agree.
But there is something that bothers me about that theory!

At what point is the combustion chamber under vacuum ?

I guess when the piston is going down there's a vacuum in the chamber for a split second before the transfers fill completely

 

[Adirondackstihl]

I guess when the piston is going down there's a vacuum in the chamber for a split second before the transfers fill completely

Wouldn't there be pressure from the expanding gasses?

 

[mdavlee]

Wouldn't there be pressure from the expanding gasses?

Somewhat. There's a time when the transfers and chamber are equalized at bdc.

 

[Knobby57]

2 stroke . Fires every other rotation . After the power stroke it will miss the next and that's when it will pull in air and give you a lean charge . Faulty decomps have trashed many saws


Sent from my phone when I should be working

 

[Adirondackstihl]

2 stroke . Fires every other rotation . After the power stroke it will miss the next and that's when it will pull in air and give you a lean charge . Faulty decomps have trashed many saws


Sent from my phone when I should be working

Nope
A saw fires every rotation.
Each time that magnet crosses the coil you have spark. That's every 360 degrees.

 

[Knobby57]

Nope
A saw fires every rotation.
Each time that magnet crosses the coil you have spark. That's every 360 degrees.

You are correct sir . I think I need more sleep [emoji42]


Sent from my phone when I should be working

 

[Homelite410]

But....... You do need a saw to four stroke....... Right Jeremy?





"I have a potty mouth".............[emoji8]

 

[Adirondackstihl]

But....... You do need a saw to four stroke....... Right Jeremy?





"I have a potty mouth".............[emoji8]

It was 4 strokin quite readily and cleanup up in the cut.

 

[Homelite410]

That's what we like! Put that decomp in another saw and see if you get the same damage!

 

[Adirondackstihl]

That's what we like! Put that decomp in another saw and see if you get the same damage!

I'll send it to you for further analysis

 

[old-cat]

I think there was trash getting in there.

 

[Duke Thieroff]

That looks like molten aluminum, not debris ingestion.

What do I know though...pics ain't the best.

J, can you advise?

 

[Duke Thieroff]

Pics of piston?

 

[Adirondackstihl]

I don't think ingestion would cause transfer. Not in 3-4 tanks of fuel

I'll get some piston pics in a lil bit

 

[big t double]

Was it snowing or raining when you were cutting? Any possibility there was moisture in your fuel? Usually scoring on the intake side only is from something washing the oil/lube off the intake side...also known as water score. Condensation forming in the carb maybe from cold temps? Or debris ingestion but like you said...debris probably wouldn't cause the transfer. Something had to of washed that cylinder. My .02.