My 3120xp mods, share yours and or your opinions

[kneedeepinsaws]

Bought this saw to replace my 395 for milling, out of the box I was a little disappointed to be frank.
I did a couple things to make it a little more fun to use and more reliable for milling.


air filter
Not the best setup cause it was passing particulates, I didnt want any dirt in the engine if I could help it. So i took the flock filter and ran a thin layer of RTV black on the sealing edge of both sides. I worked it in and ran it smooth with my finger. Let dry and used grease to make a good seal. This shot of the intake horn is after two tanks today, extremely clean air going in now
Theres some gunk near the top cause some sawdust fell in when i took the top off. If you look down into the horn it is clean
next was the coil, got an unlimited china one off of ebay, I believe it was a 272 coil. If i could find an OEM one I will probably swap it out. But it is working fine. Combine this with the carb mod from mastermind and you can now tune the saw properly. I set mine at about 10.4K or so, seems to run well with the muffler mod you will see here shortly.

next is the adjustable carb. Mastermind sold me this and he did a very nice job. The air horn must be modified in order to accept the adjustable high jet screw, uses an allen key instead of a slotted screw driver. This is a lousy shot but you can see the high jet and some of air horn removed to accept it. When you buy this you get a brand new walbro carb to replace your stock one. Thanks mastermind this is the bread and butter of this saw IMO

 

[kneedeepinsaws]

Next is a basic muffler mod, this saw had a very small baffle for exhaust gasses to escape, i just opened it up to full size with a dremel exposing the internal pipe.


next is a sticker for your country of residence. Instant 30% horse power and throttle response


stihl elasto start. I bought this to help with the snap back from the flywheel tugging on the starter cord when the engine dies. It did not work for that at all, and ill have to mod the clutch cover and ring the cord slides into to do it properly. I did however find that the saw was much easier to start!



Finally the clutch cover. I found an area near the chip deflector cut out that seemed to be just blocking chip flow. I think the lug that was there was meant for structural support in case the saw were to fall on this area. I ground it off to give a full path for chips to fly out. You can see the metal ground off near the inside of the deflector, unfortunately i do not have a before shot.

 

[drf256]

I have limited experience, but some with my 3120.

Did your saw have a green factory coil? If it did, you’re good to go with the 272 coil. If you had a factory black coil, the timing will be way off. 2 different flywheels over the years.

Im using the factory foam air filter and cage on mine.

After some break in, I set my Masterminded carb to around 12500 and the saw came alive. I initially added a flywheel side deflector to mine which worked out well, as it would direct exhaust away from me while milling, but it did get my hand kinda hot.

Now my saw is a @Moparmyway beast. Kevin did his magic inside and added a big ole pipe out the fly side of the muffler to direct heat and gasses away from me. I haven’t wanted to try it yet, as the 90* weather and milling kinda don’t jive. But from Kiev’s test vids, it’s a beast.

 

[kneedeepinsaws]

I have limited experience, but some with my 3120.

Did your saw have a green factory coil? If it did, you’re good to go with the 272 coil. If you had a factory black coil, the timing will be way off. 2 different flywheels over the years.

Im using the factory foam air filter and cage on mine.

After some break in, I set my Masterminded carb to around 12500 and the saw came alive. I initially added a flywheel side deflector to mine which worked out well, as it would direct exhaust away from me while milling, but it did get my hand kinda hot.

Now my saw is a @Moparmyway beast. Kevin did his magic inside and added a big ole pipe out the fly side of the muffler to direct heat and gasses away from me. I haven’t wanted to try it yet, as the 90* weather and milling kinda don’t jive. But from Kiev’s test vids, it’s a beast.

Yes i found out yesterday milling that this heat is too much for the saw. She vapor locked after 5 passes, so i shut her down. I realized its gonna take at least an hour for her to cool down so i packed up... too bad.

yes mine had the green coil back and if you look in the pics i added a 272 coil. I would like to see the foam filter setup you have

 

[Billy Currie]

Yikes! I thought the 3120 would have worked better for milling than that. Sorry to hear it didn't work well.

 

[Lightning Performance]

Yes i found out yesterday milling that this heat is too much for the saw. She vapor locked after 5 passes, so i shut her down. I realized its gonna take at least an hour for her to cool down so i packed up... too bad.

yes mine had the green coil back and if you look in the pics i added a 272 coil. I would like to see the foam filter setup you have

Maybe you should play with the ignition timing.
Ran off tank after tank in this weather with a 660 and the 084's

I do keep melting the buttons off of decomps on the 660 but no other issues. Not my norm but I'll take it. Zero other issues after swallowing a decomp a few weeks ago. They just need better buttons. Threading the next one for nuts. Melted a TS400 decomp last time

 

[kneedeepinsaws]

Maybe you should play with the ignition timing.
Ran off tank after tank in this weather with a 660 and the 084's

I do keep melting the buttons off of decomps on the 660 but no other issues. Not my norm but I'll take it. Zero other issues after swallowing a decomp a few weeks ago. They just need better buttons. Threading the next one for nuts. Melted a TS400 decomp last time

Do you think retarding it just a degree or two would help cool it down?

 

[rogue60]

Vaper locking that's odd sounds like its the fuel to me.
I've run a 3120 in 40c 100f heat all day many tims never had it vaper lock but that was a few years ago when pump fuel was good and not the rubbish they sell now days that boils at a much lower temperature made only for high pressure heat shielded constant circulating fuel systems in modern car's.

 

[kneedeepinsaws]

I might have tuned it too lean... hmmm maybe i should do a vac test on it...

 

[Nutball]

Maybe you should play with the ignition timing.
Ran off tank after tank in this weather with a 660 and the 084's

I do keep melting the buttons off of decomps on the 660 but no other issues. Not my norm but I'll take it. Zero other issues after swallowing a decomp a few weeks ago. They just need better buttons. Threading the next one for nuts. Melted a TS400 decomp last time

The OEM Stihl valves have wings stamped into the shaft so I thought, so they can't fall into the cylinder.

 

[Stump Shot]

The OEM Stihl valves have wings stamped into the shaft so I thought, so they can't fall into the cylinder.

There's only a tiny hole on the inside of the cylinder.

 

[Nutball]

Which is why Husqvarna is lotz better, but you will see I was replying to a Stihl post.

 

[Lightning Performance]

Vaper locking that's odd sounds like its the fuel to me.
I've run a 3120 in 40c 100f heat all day many tims never had it vaper lock but that was a few years ago when pump fuel was good and not the rubbish they sell now days that boils at a much lower temperature made only for high pressure heat shielded constant circulating fuel systems in modern car's.

Good point. Try avation fuel to cool it down. Better fuel and all gas.

 

[Lightning Performance]

The OEM Stihl valves have wings stamped into the shaft so I thought, so they can't fall into the cylinder.

Not all of them were pinched enough. I did one on an 066 that ate a decomp. Both were oem.
I drilled out that stock 660 that fell in with three 1/64 holes. It's getting threads and a nut. lock the nut, peen the end and a dab JB should do.
The AM decomps are gone in five minutes. The button oozes over and the tension is long gone on the fingers in one tank. Not on my saws thank you. Hobby time is over. Quality chit ftw.

Do you think retarding it just a degree or two would help cool it down?

What type an octane fuel you burning?
Go there first.

 

[Stump Shot]

Which is why Husqvarna is lotz better, but you will see I was replying to a Stihl post.

Sorry I was cornfused.

 

[kneedeepinsaws]

Not all of them were pinched enough. I did one on an 066 that ate a decomp. Both were oem.
I drilled out that stock 660 that fell in with three 1/64 holes. It's getting threads and a nut. lock the nut, peen the end and a dab JB should do.
The AM decomps are gone in five minutes. The button oozes over and the tension is long gone on the fingers in one tank. Not on my saws thank you. Hobby time is over. Quality chit ftw.

What type an octane fuel you burning?
Go there first.

I run shell 92 octane no ethanol with maxima k2 at 40:1

i tuned it to 10.6 but i didnt tune it after the first cut which is the most important cause thats when its warmed right up.
I wont say that it vapor locked completely but i could tell it was starting, it was leaning out real bad after the 5th pass with high rpm. I tried dumping more fuel in the high jet but it only worked for a moment then went lean again. Brought it home and fired it up and retuned the high back to approx where it was and it was running fine

 

[huskyboy]

Leaning out on the H midcut? Sounds like it could be a airleak or a carb issue...? Idk how a 3120 is setup but if it’s like a 394.... it’s very easy to bugger those carb/intake manifold gaskets upon installation if your not careful. Also the intake blocks can crack. I’ve had vapor locking happen to me on other saws. When that happened to me the saw just refused to start and I proceeded to get pissed off lol. Leaning out on the H scares me... if that is what is really happening to you though. Could be something to look into.

 

[Deets066]

Maybe you should play with the ignition timing.
Ran off tank after tank in this weather with a 660 and the 084's

I do keep melting the buttons off of decomps on the 660 but no other issues. Not my norm but I'll take it. Zero other issues after swallowing a decomp a few weeks ago. They just need better buttons. Threading the next one for nuts. Melted a TS400 decomp last time

Pics of a melted button

 

[kneedeepinsaws]

Leaning out on the H midcut? Sounds like it could be a airleak or a carb issue...? Idk how a 3120 is setup but if it’s like a 394.... it’s very easy to bugger those carb/intake manifold gaskets upon installation if your not careful. Also the intake blocks can crack. I’ve had vapor locking happen to me on other saws. When that happened to me the saw just refused to start and I proceeded to get pissed off lol. Leaning out on the H scares me... if that is what is really happening to you though. Could be something to look into.

The reason i wasnt too concerned is cause other people have reported vapor lock with this saw.

I will look into it though, you got me thinking now...

 

[kneedeepinsaws]

The OEM Stihl valves have wings stamped into the shaft so I thought, so they can't fall into the cylinder.

Lmao haha