Part One: The Exhaust Port

[CJ Brown]

Notice how the top ring is polished, and the second ring is hardly broken in? To me that says the second ring isn't doing much of anything, except slowing the saw down.

 

[XP_Slinger]

Both rings look pretty evenly worn to my eye. Anybody ever test for a differential in compression with the bottom ring removed?

 

[mdavlee]

5 lbs is about normal. 2nd ring transfers some more heat to the cylinder. How much I'm not sure.

 

[Chainsaw Jim]

Notice how the top ring is polished, and the second ring is hardly broken in? To me that says the second ring isn't doing much of anything, except slowing the saw down.

The bottom ring is weaker than the top. Off the piston relaxed it has .040 less gap.

I did notice there's a little bit of wear on the top edge of the bottom ring. It isn't noticeable with the naked eye, but shows up good in a picture.
I was expecting to see something like that on the ring after finding that rough plating across the center of the exhaust roof.
It makes me wonder how many 034s saws failed due to that design.

 

[CJ Brown]

Does the lower ring come from the factory with less tension? In other words, if you buy a set of rings for an 034, do you have to ensure that they are installed in specific grooves according to their gaps? The top ring will be forced hard against the cylinder wall by combustion pressure, causing more wear to the top ring than the bottom one, as the bottom one sees much less pressure during combustion. I have no idea how much the increased heat and pressure affects the top ring over time.

 

[drf256]

Good question.

I'm pretty sure top and bottom are the same tension.

Some guys like to use a new top ring with an old bottom ring when they port a saw. You get a bit less parasitic drag with the same heat transfer.

 

[Deets066]

You'll have less skirt wear with both rings in

 

[PogoInTheWoods]

Does the lower ring come from the factory with less tension? In other words, if you buy a set of rings for an 034, do you have to ensure that they are installed in specific grooves according to their gaps?

No.

 

[Deets066]

Revival of the dead thread

 

[Moparmyway]

One could drive a truck through that opening

 

[GoBigBlue1984]

View attachment 89183

View attachment 89184

Revival of the dead thread

That's purty!

 

[XP_Slinger]

Nice work as always. What Saw ya working on?

 

[Mastermind]

Very slick Deets......very slick.

 

[Deets066]

Nice work as always. What Saw ya working on?

066

 

[Deets066]

 

[TreeLife]

Oh wow...nice work Deets!

 

[Deets066]

Oh wow...nice work Deets!

Thanks! Still has the stock muffler on it. She will come right to life after I'm done

 

[TreeLife]

Thanks! Still has the stock muffler on it. She will come right to life after I'm done

Hopefully some before and afters

 

[Nc grease monkey]

Has anyone tried stepping the exhaust port down? If I'm thinking correctly the expanding gases coming out of the top of the port first then being forced down should create a low pressure area at the bottom of the port and help aid in scavenging?

 

[huskihl]

Has anyone tried stepping the exhaust port down? If I'm thinking correctly the expanding gases coming out of the top of the port first then being forced down should create a low pressure area at the bottom of the port and help aid in scavenging? View attachment 95146

Dolmar 7910 series are like that