Tuning your 090

[Spokerider]

Wondering how you guys tune your 090 for milling?

Been reading that it *should* be tuned richer for milling......
ok, so how MUCH richer?

Just put a NWP kit on the 090 and it's not had a tank of gas through it yet.
Using Amsoil Saber at 40;1, Chevron Supreme Plus gas, new filters etc.
I have the service manual, and it says to tune the saw to 11 000 rpm with the fan air-driven limiter disabled, and then to enable the limiter again and set the wire on the limiter to achieve a max rpm of 8000.

So if 11 000 rpm is *baseline* for bucking / falling, how much richer should it be set for milling? I'm guessing that to make it richer using the tach, one would look for an rpm of say.......9500-10 000 with the limiter disabled and then keep the max rpm at 8000 via the limiter wire. Thoughts?

 

[Grande Dog]

Howdy,
When you adjust it with the governor disabled, adjust the same as you would any other saw. Instead of looking for a number, you look for a good burble. Since the governor is air vane, and hooked directly to the choke (rather than being an electronic limiter), it cuts off the air supply making the saw run richer (thereby cooling) to slow it's roll. Around 8400 governed under load is a good general setting. If you're going to run a steady diet of small, or large wood past it, you might want to adjust the governor a notch or two.
Regards
Gregg

 

[Spokerider]

Gregg,
Thanks for the reply.
I'm not sure what you're saying, so let me reiterate........

Tune the saw, in the cut under load, with the vane gov disabled, so as to get some 4 stroking......rpm is irrelevant. Then re-hook the gov up and adjust the wire to get a max rpm of 8400 in the cut, under load. Correct?
Will this adjust the saw richer than 11 000 rpm / no load / gov disabled?

I understand how the air vane works by richening the mix and thus limiting the rpm, and that by running the saw WOT with the air vane limited rpm, that this richened mix is advantageous to engine longevity under milling load. What about the air fuel mix at part throttle? [ not that I will be running part throttle much if at all ] Will it be rich enough?

I have not tried to tune the saw yet, as I am still waiting on the arrival of the 20K tach,

 

[Grande Dog]

Howdy,
Yes, that is correct on the adjustment procedure. The governor in this application is to prevent no-load high rpms. Part throttle air mixes are an issue with all saws. If you hunt around with the throttle you can find a flat spot where the low-speed / fuel pump circuit drops off, and the high-speed / venturi circuit picks up. When it's tuned right, it'll sound like it can barely get out of it's own way but, you can really lean on it for torque. Unless you're making huge cuts, it'll never 2 cycle.
Regards
Gregg