Christmas Exchange Echo 620

[Four Paws]

I've been looking for ways to improve flow and I see a lot in this cylinder that use to be done for improvements over the years.

I won't touch the transfers. I may widen the exhaust. Intake will end up where setting squish leaves it.

Have you found any areas where you can improve flow?

I find it interesting, but not surprising, that the decomp disturbs the flow in the combustion chamber so much!

What about carburetion? Intake timing is long - what is the venturi diameter? Do you feel a larger venturi would help?

 

[Mastermind]

I won't touch the transfers. I may widen the exhaust. Intake will end up where setting squish leaves it. This saw is like playing chess, I need every move to count.

I ordered a base gasket, it will probably take a few days to get.

Chess huh? I like chess.

 

[Stihlbro]

Have you found any areas where you can improve flow?

I find it interesting, but not surprising, that the decomp disturbs the flow in the combustion chamber so much!

What about carburetion? Intake timing is long - what is the venturi diameter? Do you feel a larger venturi would help?

I seen the decomp markings too, around it is the only area with some build up. Might be the oil I'm using????? Lol!

I've compared the carb to other models of the same size and it is very equivalent in size. But....I got a idea. I'll show some measurements after a while.

Chess huh? I like chess.

Did you like my wording? Got to think this thru, got to have a plan. Personally I could leave it stock and be happy. I've ran it enough to know it is sassy from the factory.

 

[Mastermind]

I seen the decomp markings too, around it is the only area with some build up. Might be the oil I'm using????? Lol!

I've compared the carb to other models of the same size and it is very equivalent in size. But....I got a idea. I'll show some measurements after a while.



Did you like my wording? Got to think this thru, got to have a plan. Personally I could leave it stock and be happy. I've ran it enough to know it is sassy from the factory.

It reminds me of the Solo 681. Tough to make gains on in a real working environment. I stared at this saw long and hard myself.

 

[Red97]

Have you found any areas where you can improve flow?

I find it interesting, but not surprising, that the decomp disturbs the flow in the combustion chamber so much!

What about carburetion? Intake timing is long - what is the venturi diameter? Do you feel a larger venturi would help?

Same as the hda 199 around 15.9 mm IIRC. the boot is the tight spot, but don't think it hinders much.

 

[Stihlbro]

Squish set at 18 thousands. Ports untouched. The piston has washers in between the piston and rod. What a pain to get back together.

I won't have a base gasket till later in the week.

The piston is tapered and the squishband is tapered. Very hard to get squish clearance readings.


Flow?

Maybe here?

 

[exSW]

The piston has washers in between the piston and rod. What a pain to get back together.

That 680 piston I just pulled is the same way.

 

[Red97]

Squish set at 18 thousands. Ports untouched. The piston has washers in between the piston and rod. What a pain to get back together.

I won't have a base gasket till later in the week.

The piston is tapered and the squishband is tapered. Very hard to get squish clearance readings.


Flow?
View attachment 45339
Maybe here?

Washers are to keep the rod centered on the crank, vs floating around, creating odd pressure angles. Just a dab of grease does wonders.

Leave that piece in the filter, otherwise ya gotta wring the fuel out every couple days... I removed it on one saw, didnt notice anything performance wise. With the intake in 80*+ range they start spitting pretty good.

 

[Stihlbro]

I won't take it out, may add some holes in the sides.

Small increase in cranking compression.



Made some spacers and drilled a Stihl bar to run a more common chain.

 

[Four Paws]

They was a nice bump in compression, Joey.

 

[Deets066]

How much did you drop the jug Joey?

 

[Stihlbro]

I dropped the jug a total of 20 thousandth. .012 gasket and .008 off the base.

 

[Four Paws]

How much skirt do you have left at TDC?

 

[Stihlbro]

I did not get an exact measurement. It will be apart again once I get the base gasket.

 

[Bigblock]

Subbed

 

[drf256]

Any reason you can't lose the lower ring and run the piston in the correct orientation?

Great build Joey. With the amount of carbon I see on that piston, how long do ya think the 18 squish will hold up?

This saw was new when you got it, correct?

Is that oil or scoring in the bore?

Other than widening the exhaust, and maybe a little epoxy on the intake floor, I can't see anything to gain by touching those myself.

 

[drf256]

BTW,

The 490 had the same odd ring pin setup. I had to lose the lower ring to get where I wanted to be on the intake.

 

[Stihlbro]

Can't do much with piston.

18 on squish is way too tight for me. It is temporary.

This is a brand new saw with 3 tanks of fuel thru it.

The picture make the cylinder look worse than it is. There are some shiney spots, again new saw.

This saw is gonna be hard to get much improvement, but I have a plan.

There just ain't no love for an Echo it seems.

 

[Red97]

I like echo...

 

[drf256]

I like echo...

Me too.

I'd be proud to own/win it. Very happy Joey.

Does look tough to improve.

They're like the Honda of Chainsaws. The 620 is more of an Acura.