Tuning a saw to factory RPM while increasing oil % in mix

[John J.]

I have a strato Ms 391 and a Husky 3120xp I recently removed the limiter caps from the 391 and I'm having a hard time tuning it by ear for the -High- I was almost 2 turns out for 4 stroking by my ear,I have good hearing but not that sensitive to sound change. I initially was going to tune by tachometer and slightly richen the mixes but my cheapo tachometer is jumping 600+/- rpm so I left the saw as is until I receive my new tachometer in the mail.
Here's my questions:

*********-If I increase the oil ratio in my ms391 and tune to spec rpm (idle/under factory max) is it still getting adequate fuel at that rpm being a slightly more viscous mix?*********

-My 3120xp seems to run rich based on exhaust and plug knowing that the European manual states 33:1 for proper mix and I've been running 50:1 if I just switched to 35/40:1 would that be okay and possibly run more lean?

I want a richer mix because these saws will be used for milling the 391 very small logs and the 3120xp for everything else.

 

[Andyshine77]

Both saws are revlimited so tuning for maximum rpm without load can be difficult. Your tachometer is likely jumping around because the signal is being cut by the limiter. The best option is to tune in the cut, or with a tachometer you can set the rpm's just under the limiter.

Don't over think the ratio change, it does have some effect, but not all that much.

 

[Little Al]

We run our 3120's at 35/1 in a commercial falling setting not had any problems, tuned in the the cut If you are not used to a limited coil it can be a bit "iffy" working out if it's coil cutting out or 4 stroking it"s a practice makes perfect sort of thing.

 

[SeMoTony]

I have a strato Ms 391 and a Husky 3120xp I recently removed the limiter caps from the 391 and I'm having a hard time tuning it by ear for the -High- I was almost 2 turns out for 4 stroking by my ear,I have good hearing but not that sensitive to sound change. I initially was going to tune by tachometer and slightly richen the mixes but my cheapo tachometer is jumping 600+/- rpm so I left the saw as is until I receive my new tachometer in the mail.
Here's my questions:

*********-If I increase the oil ratio in my ms391 and tune to spec rpm (idle/under factory max) is it still getting adequate fuel at that rpm being a slightly more viscous mix?*********

-My 3120xp seems to run rich based on exhaust and plug knowing that the European manual states 33:1 for proper mix and I've been running 50:1 if I just switched to 35/40:1 would that be okay and possibly run more lean?

I want a richer mix because these saws will be used for milling the 391 very small logs and the 3120xp for everything else.

The air to mix ratio stays same in older manual adjust carbs til needle is turned.Raising oil% in mix lessens out gas to air ratio thereby leaning just the burn. These newer self adjusting saws are just "majic" to me & I don't know if it be good majic or black majic (-;

 

[John J.]

Finally got my Fast-Tach in the mail seems to work okay have to move it around to find the super sweet spot, I'm not experienced in tuning at all I play with my Mac 10-10 just for practice but what a different animal these new saws are.
I tried tuning the stilh 391 based on rpm Low/High and Idle but I gave up with that so I tuned Low on the saw roughly half way between lean stall and rich stall range was about 7/8 turn back and forth tried to center. Then set Idle to 2800.
High I started out 1 to 1-1/4 out and only raised the rpm to a max of 11750 feeling a bit poosey rather keep it rich What's the max rpm 13k? 2800k idle??
Am I doing it right? Lol

3120xp set a max rpm of 7200 WTF is up with that?? Is it possible that it would increase rpm in the cut near 8-9 k?
I have the tach set at 360 one spark per revolution

 

[hedge hog]

Someone will chime


Sent from my iPhone using Tapatalk

 

[John J.]

Bump. Threads seem to drop quick on this site I must say. What's up bros

 

[Andyshine77]

Well I don't have a fast tach so I'm not familiar with it's settings, but it sounds like you have it on the correct setting. A 391 should at a bare minimum spin 12,500 before the tachometer starts to just around. Not too familiar with the 3120 but I do know they are limited to really low rpm's. The carbs can be modified and different coils can be used.

Sent from my HTC One_M8 using Tapatalk