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Mufflers and jetting/tuning

Started by alleyyooper, December 09, 2010, 03:23:47 PM

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alleyyooper

Jonsered 2159C hot handle due to EPA cat muffler. I bought the saw in the fall of 2004.




Can replace it with a non EPA non cat muffler for a resonable price.



Is the change going to require a big jetting change?

;D  al

your not fully dressed with out a smile.

JohnG28

Welcome to the forum alley.  Do you mean will the carb need to be retuned after installing the new muffler?
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

JohnG28

I guess I should have paid more attention to the title of the thread here, sorry.  Most likely you would need to retune your carb following a muffler change or modification.  Probably need a little richer on H side until it four strokes.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

John Mc

I made exactly that swap on my Jonsered 2152. All it needed after the swap was a tweak of the high speed mixture to richen it up a bit. I did have to trim the limiter caps on the mixture screws to get the adjustment needed. Saw runs significantly cooler, and has a bit more power.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

dsgsr

What's it mean when the term (when it fourstrokes) is used?

Thanks,
David
Northlander band mill
Kubota M59 TLB
Takeuchi TB175 Excavator
'08 Ford 550 dump
'87 International Dump
2015 Miller 325 Trailblazer Welder/Gen

JohnG28

I didn't know that myself until learning from the guys here.  It's when the motor sounds sort of rough at WOT with no load, similar to a small 4 stroke engine, say a 4 stroke weedeater, if you've heard one run.  It's hard to explain really, but there was a thread a while back where someone, I believe Cut4Fun, posted few videos of what you should listen for.  Makes it a lot easier when you can hear it for yourself.  Once you get it right with no load, when you bury it in a cut it smooths out and has more power.
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

John Mc

when setting the high speed mixture, if it's too lean at wide open throttle (WOT), you get a "screaming" sound (if you lean it even further, the saw won't run). If you enrichen it a bit, the saw runs smoothly. Keep going richer, and the saw starts to "blubber". With a bar and chain on the saw, but out of the wood (no load) you should enrichen it until it just starts to "blubber". This is the 4-cycle sound you've heard people refer to. When you put the saw in the cut under load, the blubbering smooths out to the normal two-cycle sound.

Madsens has a good write up of this, as well as an audio file you can listen to as someone adjusts the saw between, normal, lean, and rich settings. You can find that article here:
Madsen's Saw Carb Tuning

Other interesting Madsens files: http://www.madsens1.com/MNUsawmaint.htm

John Mc
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

dsgsr

Northlander band mill
Kubota M59 TLB
Takeuchi TB175 Excavator
'08 Ford 550 dump
'87 International Dump
2015 Miller 325 Trailblazer Welder/Gen

alleyyooper

It is also a good idea to learn how to read your spark plug.

Do I just snip off the limmiters on the 2159 so i can adjust the carb or do I have to remove a part to remove the limiters.

On the husky 55 they were just winged caps that slid off once you removed the top cover.

;D  Al
your not fully dressed with out a smile.

sharkey

What's it mean when the term (when it fourstrokes) is used?

When there is no load on the engine the piston can move though its power stroke pretty much uninhibited.  Because of this 'no load' situation, the fuel is not always fully burned during the power stroke.  So when adding a load, the engine rpm slows down while cylinder pressure and heat increase.  The load or weight on the engine keeps the burning fuel contained within the cylinder for a longer period of time helping to achieve complete combustion and greatest power.     

You can hear this by listening to the exhaust sound of the engine.  When the fuel mixture is not fully burning, the engine sounds like its firing on every other cycle or burbling like an old Lawnboy mower.  When adding a load by beginning a cut, the burble goes away.  If the burble doesnt end when the load is applied, then the mixture is considered to be too rich with fuel for the amount of air/oxygen that is available for combustion in the cylinder.         

To further your interest, gasoline as a fuel has a stoichimetric combustion ratio that it burns the best at.  This fuel to air ratio is where complete combustion occurs. Therefore all of the fuel which has been metered through the carb and mixed with air, is compressed by the piston and burned in the cylinder to be made into power.  Complete combustion is when all the parts of the fuel are converted. 

All two stroke engines need to be run a little on the rich side to compensate for changes in temperature, barometric pressure, load and so on.  Just thought you might want to do a little more reading about how some of these things work. 

 

   


Captain


John Mc

Quote from: sharkey on December 18, 2010, 06:15:22 AM
To further your interest, gasoline as a fuel has a stochiometric combustion ratio that it burns the best at.  This fuel to air ratio is where complete combustion occurs. Therefore all of the fuel which has been metered through the carb and mixed with air, is compressed by the piston and burned in the cylinder to be made into power.  Complete combustion is when all the parts of the fuel are converted.

To expand on that a bit: the stochiometric ratio of air to "straight" gas is 14.x to 1  (14.7 ??) The ratio for straight ethanol is closer to 9:1 (ethanol is an "oxygenated" fuel - some of the oxygen need for combustion is already in it, so you need less oxygen from the air). So the mixture needs to be set differently for your saw if you are running pure gas versus running 10% ethanol gas (E10). If you are set up for pure gas, then put in E10 (or E15, which I hear will be coming soon), you'll need to readjust the carb for best operation -- otherwise, your saw will be running a bit leaner with E10 than it did with pure gas.

Modern cars, and some newer "auto-tune" saws can do this automatically. Older cars, most chainsaws, and many small engines need to be retuned (and some will not run well even with retuning... might need a new carb or ??, not to mention ethanol resistant fuel lines, tank sealants, diaphragms and O-rings)

Clear as mud?
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

dsgsr

Yes, clear as Mud :D But Thanks for all the effort. I'm a slooow learner but once I've got it:) i'll be happy as a pig, in Mud.


Thanks,
David
Northlander band mill
Kubota M59 TLB
Takeuchi TB175 Excavator
'08 Ford 550 dump
'87 International Dump
2015 Miller 325 Trailblazer Welder/Gen

Cut4fun

Listen to this Dolmar 166 of mine. It is set fat and 4 stroking out of the wood. Once in the wood and cutting you will here it clean up in the cut.

http://www.youtube.com/watch?v=YqXOHsQE3Wk

JohnG28

That's was the video I was thinking of.  8)
Stihl MS361, 460 & 200T, Jonsered 490, Jonsereds 90, Husky 350 & 142, Homelite XL and Super XL

dsgsr

Thanks cut4fun, I needed to hear it I understand now.


Thanks,
David
Northlander band mill
Kubota M59 TLB
Takeuchi TB175 Excavator
'08 Ford 550 dump
'87 International Dump
2015 Miller 325 Trailblazer Welder/Gen

tonto

Stihl MS441 & Husqvarna 562XP. CB5036 Polaris Sportsman 700 X2. Don't spend nearly enough time in the woods.

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