Chainsaw Porting Theory

[Brush Ape]

I'm right there with you Al. Loving the atmosphere of this place. Respectful.....that's what it is.

You have to respect Al the guy's slung like a Bull Ardvark.

 

[paragonbuilder]

You have to respect Al the guy's slung like a Bull Ardvark.

It's amazing what you can do with shadows and light placement! [emoji23]


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[Al Smith]

Have u ever followed the tuning in the Stihl service manual? After several up and downs on rpm between the idle and the l the final idle is set with the l

I had sent a carb to Eddie Anderson at Stihl in Va Beach for evaulation .He sent me a new one ,Zama C1Q something for a 200T .I never as much as turned a screw on it and it was right on the money .However it came with instructions that would have taken 20 minutes to dial it in .Way too much info .

 

[5000+]

Absolutely, unless you are cutting at high elevations. Compression increase is a power adder. Too much compression can work against you in a work saw. Work saw I'm classifying a saw saw that runs all day. Not the one truck load firewood cutters. Not your 3 minute YouTube videos.

I'm not saying it's not done, or I am right. I am speaking of my experiences from my uses. The closer I get to 200lbs of cranking compression the more I find tunes change with saw getting to operating temperature. Cold saw it so rich it won't rev up till it gets to temperature.

Saw with closer to 175/185 seem to perform better from start to finish. Make sense?

Stock saws once tuned in, have you ever had to retune once dialed in in same cutting conditions?

Lots of old big jonsereds had over 200#s stock. They held tune good, but they were not super high revving screamers like more more modern saws.

 

[weedkilla]

So I've come to learn that "4 stroking" occurs when the mix is too rich to fire. So that combustion cycle goes unburned, and then it mixes with some exhaust days and ignites on the next cycle. If it takes 2 cycles, then it's "6 stroking".

I'm having a hard time understanding why an engine goes from 4 stroking with no load to 2 stroking under load.

You lay the chain into wood, so now you have resistance.

Does the motor suddenly have more chamber heat to burn the mix better?

What's actually happening?

My understanding is that with a carb like you find on a saw it pulls more fuel with increased air velocity, as the revs drop when you hit the wood you pull a little less fuel.
I can't see the heat change being the instant change you see in most saws where you can lift in the cut and the saw goes straight back to 4 stroking.

 

[Deets066]

That's how I tune one,haven't fried one yet. Lol

Lot of times my low will be less than a turn and my high will be over a turn,not much either way though,maybe a 1/8 of a turn and lean cold.

Most of the time my saws tune over 1 on the low, throttle response seems to improve with the low opened up good. I always start at 1-1/8 and go from there

 

[Keith Gandy]

I had sent a carb to Eddie Anderson at Stihl in Va Beach for evaulation .He sent me a new one ,Zama C1Q something for a 200T .I never as much as turned a screw on it and it was right on the money .However it came with instructions that would have taken 20 minutes to dial it in .Way too much info .

Wow!! Anyway u can copy and paste that?

 

[Al Smith]

I have an 038 mag I tweeked .Pop up piston,long sweeps on the upper transfers,muffler reworked, piston, the whole nine yards .It starts hard after sitting for a long while but after that fires on one tug .Never runs hot even in 90 degree weather .

It has a D-handle because the comp is high but I'm at elevation 800 or so feet above sea level if that has anything to do with it .One thing, it almost never sits at idle .It's either running wide open or off .

 

[Al Smith]

Wow!! Anyway u can copy and paste that?

I think I have the box the carb came in on my other computer desk,I'll check.

 

[Keith Gandy]

I think I have the box the carb came in on my other computer desk,I'll check.

Thanks

 

[Deets066]

Most of the time compression is just a by product of other desired mods

 

[Al Smith]

Well I found the box,part number 1129-120-0653 .Zama c1Q s126a .Nice diagram how to install it with a various type of elbows for the intelicarb set ups . .Problem,no tuning directions .I tried ..

 

[Keith Gandy]

Well I found the box,part number 1129-120-0653 .Zama c1Q s126a .Nice diagram how to install it with a various type of elbows for the intelicarb set ups . .Problem,no tuning directions .I tried ..

Thanks anyway

 

[Barneyrb]

I've seen the tune issue that Joey is talking about. But......only in a few saws. The worst one is my Poulan 3750. Tune it perfect....then make a dozen cuts. It's screaming lean. Retune, and it's good to go......till it cools off. Then it's so fat it will hardly run. I was seeing that to some extent in the MS461 too. After I started drilling the main jet, that issue went away.

Randy, on that Poulan I found if you use the metal throat insert and the outer ring from a Stihl ( I don't remember the model I used one from) but it helps. Does it have a 137 or a 164 on it?

 

[riverrat2]

I wish diesel pickups were as easy as chainsaws to make power. Put higher flowing injectors in, advance timing, now we have to upgrade the clutch or automatic trans to start. I have grenaded enough parts already in my truck.

But I still want more power... next is turbos, even larger injectors.... when does it end? I smell smoke coming from my wallet.....

Connecting Rods sticking out the side of the block once or twice will get that out from under your skin!!!!! Usually!!! LOLOL!!!

 

[Dieselshawn]

riverrat2: That could likely happen, but I'm keeping my rpms below 2,500 rpms while making power. Cummins do not like high rpms. People run high rpms because quick power can be made and will save a lot of grief for anything sitting behind that six shooter.

I on the other hand am trying to keep everything from failing behind the engine by beefing them up. The engine is fine, very well built.

 

[Ironworker]

While I tune my saws, I also check throttle response, I like to leave my l somewhere between chain spinning on its own and good throttle response, I hope that makes sense.

 

[riverrat2]

The load on a WOT chain is minimal and does little work, when you put the chain in wood, more work is done, so more power is needed.

At no load, the tune is slightly rich for the load and we see the typical 2 stroke studder or 4 stroke. That same tune cleans up with more load, and as the load increases, more fuel is needed to cool the machine and have the necessary power to do the increased work

Absolutely, when its fours-stroking it cannot use all the fuel that is available because the RPM is too high, but when you load it up in the cut the motor slows down and the excess fuel is now more fully utilized...

FWIW I live and work within 18'-250' AMSL. on the Texas/ Louisiana Coastal Plains

I went saw racing up in TN a few times and learned real quick that my sea level tune that I use for falling/bucking timber on the landing all day is way too fat for cutting cants around 2K' AMSL LOL

Yes if you want a work saw to live around here a four stroking tune will make it last,,, and the extra fuel will keep it kool!!!! Just saying!!!

 

[riverrat2]

riverrat2: That could likely happen, but I'm keeping my rpms below 2,500 rpms while making power. Cummins do not like high rpms. People run high rpms because quick power can be made and will save a lot of grief for anything sitting behind that six shooter.

I on the other hand am trying to keep everything from failing behind the engine by beefing them up. The engine is fine, very well built.

OK yeah I got ya, I have a nice 06 Ram 3500 and just had to put a better clutch in it and all I've done is the Smarty Jr.... The dual Mass flywheel is now gone And I have a Kevlar/Ceramic button Clutch that is working verywell

 

[mdavlee]

riverrat2: That could likely happen, but I'm keeping my rpms below 2,500 rpms while making power. Cummins do not like high rpms. People run high rpms because quick power can be made and will save a lot of grief for anything sitting behind that six shooter.

I on the other hand am trying to keep everything from failing behind the engine by beefing them up. The engine is fine, very well built.

It's more fun when they hit the peg for 0 on a 12 valve.