Stihl 039 Muffler Modification Complete Applies to 029, 039, MS290, MS310, MS390

Complete Muffler Modification of Stihl 039, same work applies to the 029, 290, 390, Stihl MS290, MS310, MS390, and clones of these models by Hulzfforma, Farmertec, and Hutzl. I call it complete because unlike many modifications that put more or larger holes in the mufflers shell to assist the gases to get out, this modification does that but also removes the material inside the muffler allowing the gases to move within the muffler much better. For example the first cuttings in the video show the performance of the standard/most common type modification. In this modification you see what can be done when you have a complete modification. Once finished with any modifications to the saw that affects flow always retune the saw as necessary, and for those that still want to use the spark arrester screen, these cuts were made with the screen installed.

[@bruceschaafsma7268]

That's amazing. You see right away even without the times

[@bigjersobservations]

Thank you for your comment

[@JungleBobRepair]

Thanks for sharing.

[@bigjersobservations]

Our pleasure Bob, and we appreciate the viewing

[@adrianstefan23]

new subscriber👍👍

[@bigjersobservations]

Thanks for subscribing

[@garengtutorial8923]

Ikut nyimak

[@bigjersobservations]

Thank you

[@jojet92]

After muffler mod , did we need to tune carb?

[@bigjersobservations]

I have always had to retune after modding. Thank you for your comment

[@patrickrolf482]

Now your going to blow it up. Faster air out faster and more air in. Now you need to re-jet the carb. If you don’t that lean burn will blow it up.

[@bigjersobservations]

Thank you for your comment. I could of showed readjusting the carb. They normally run lean after the mod if you don't adjust the carb. I spun the H screw out about 3/16 of a turn then finished tuning with a different piece of wood that was not shown. I also could of max reved the saw outside the wood before and between the cuts that are in the video so you could of heard the four stroke. Thanks again for helping to make future videos better.

[@SG-ig2th]

It’s the low “L” screw you need to adjust, not the H screw. The H screw is only used to set your max RPM. Need to turn that L screw out a 1/4 turn or so to richen up the fuel/air mixture.

[@bigjersobservations]

@@SG-ig2th Thank you for your comment. I just want to make sure that you understand that both the H and the L screws are used to adjust their respective rpm by changing how lean or rich a setting is. As you change the ratio of lean vs rich you are also adjusting rpm. The simple version is: the L screw is the primary adjustment for lower rpms, and the H screw is the primary adjustment for higher rpms. The objective rpms when using respective screws are reference points in the tuning process. For example: you may have a saw that is max rpm rated for 13,500rpm but due to altitude, bar length, temperature, type of wood, and a host of issues you may need to use the 13,500rpm as a starting point and then finish tuning for optimum cutting effect "in the wood". I recommend that anyone desiring a better understanding of H and L screw adjustments, and 2 stroke theory might want to watch the following youtube video by Craig Kirkman: Episode 43: carburetor adjustment screws on 2-stroke. Many excellent videos are available on the web, and this one does an excellent job with the use of simple yet effective graphics. Thank you again for surfacing an example of another small yet important misunderstanding.

[@schlomoshekelstein908]

same saw, same mod (mostly) and i did it roughly 10 years ago. saw still runs great. i adjusted the carb but didn't rejet

[@bigjersobservations]

Thanks for the 10 year update!!!

[@dujeamizic3588]

What the hell are you doing?!Why haven't you leave original muffler as it is?When service technician hears different sound

[@bigjersobservations]

Thank you for your comment

[@dujeamizic3588]

@@bigjersobservations "thank you for your comment?!"Goood!

[@johnarnold3696]

Did my muffler like your step one and an improvement. Doesn't seem to run near as hot. I am going to order another muffler and do like you did and do step two.. I check my jetting pretty regular with just a fine tune of a screw.I am not worried about warranty as it is out of warranty.I have the stock unmodified muffler but probably never put it back on.

[@bigjersobservations]

I'm glad to hear that it is working out for you with the usual positive results. Good luck with your next step, and thank you for your comments.

[@schlomoshekelstein908]

@@dujeamizic3588 lmao u think i'm gonna take my saw to the 'service technician' and pay him $200 to work on my saw? I AM THE SERVICE TECHNICIAN