Can an auto tune carb be converted to manual needles?

[Nutball]

I've never taken apart an automatic tuning carb, but assume it has servos that turn needles right? Or some kind of electric motor moves some kind of mechanical valve. So, it should be possible to remove the electronic part and attach some sort of manual tuning device right?

Has anyone experimented with this?

 

[DND 9000]

No this is not possible. Simply forget that idea. The fuel is delivered by an electronically controled solenoid valve.

 

[Nutball]

So it's still a variable flow valve and not a pump right? It's a little hard to tell from the Stihl video.

Another question would be: will the coil still let the engine run if it detects no solenoid (if it was replaced with a mechanical valve)

 

[DND 9000]

Yes variable fuel flow, depending on the switching cycle of the valve.

The control unit will not let the engine run if there is no valve installed or the electrical connection to it is malfunctioning. In such a case you would have 2 or 3 sec. spark and then it`s shut down.

 

[legdelimber]

Never had one of theses saws in my hands, so obviously I'm just spitballing some thoughts.
I tend to still think and get ideas like I'm in a machine shop, even though I'm not anymore. (wahhh)

Has anyone tried hanging an extra solenoid as a dummy for the ignition?
Of course you'd need a way to get fuel to flow to run the engine.
A bit of something to hang the solenoid open that's still on the carb body
or just mount a non auto-tronic carb (if all that is practical)
After doing all of that....
Would the ignition get confused when it's attempts to adjust the saw RPM didn't get the expected results?
What would the module do?
Go into a "limp home" mode or just do the aforementioned brief run and shut off routine?

Heck. If the ignition would stay happy and run while hooked to a non installed solenoid...

Could someone make a "cartridge" with an adjusting screw (blunt or flat end?) to fit into the carb body where the solenoid normally fits?
Think a little bit like the old screw and bolt that held the float bowl on an older mower engine.
A Screw in the middle, but with an appropriate shaped end so as to fit the need.
Maybe the cartridge has a drilled passage and the screw works against an internal surface, thus controlling the flow through the cartridge and the carb circuit?
Or does the ignition feedback cover enough operating range that the carb lacks the old type of mid-range fuel circuitry, due to the processor, also, altering the fuel flow at speeds less than max rpm?
In other words, would it meter fuel worth a heck if you somehow popped a (properly sized)
metering orifice into the solenoid hole, to (mostly)cover max rpm in a fashion of the old screw carbs.


Is there even room, physically, to do such a thing?
Are the all of parts and saw body, air box, etc arranged in such a way as to permit it?

 

[Nutball]

Never had one of theses saws in my hands, so obviously I'm just spitballing some thoughts.
I tend to still think and get ideas like I'm in a machine shop, even though I'm not anymore. (wahhh)

Has anyone tried hanging an extra solenoid as a dummy for the ignition?
Of course you'd need a way to get fuel to flow to run the engine.
A bit of something to hang the solenoid open that's still on the carb body
or just mount a non auto-tronic carb (if all that is practical)
After doing all of that....
Would the ignition get confused when it's attempts to adjust the saw RPM didn't get the expected results?
What would the module do?
Go into a "limp home" mode or just do the aforementioned brief run and shut off routine?

Heck. If the ignition would stay happy and run while hooked to a non installed solenoid...

Could someone make a "cartridge" with an adjusting screw (blunt or flat end?) to fit into the carb body where the solenoid normally fits?
Think a little bit like the old screw and bolt that held the float bowl on an older mower engine.
A Screw in the middle, but with an appropriate shaped end so as to fit the need.
Maybe the cartridge has a drilled passage and the screw works against an internal surface, thus controlling the flow through the cartridge and the carb circuit?
Or does the ignition feedback cover enough operating range that the carb lacks the old type of mid-range fuel circuitry, due to the processor, also, altering the fuel flow at speeds less than max rpm?
In other words, would it meter fuel worth a heck if you somehow popped a (properly sized)
metering orifice into the solenoid hole, to (mostly)cover max rpm in a fashion of the old screw carbs.


Is there even room, physically, to do such a thing?
Are the all of parts and saw body, air box, etc arranged in such a way as to permit it?

I forgot it messes with the "low speed" too or something for cold starts, so defeating it might leave you without a low speed adjustment. I had thought of hanging a dummy solenoid on it, or at least a coil of similar properties, but depending on how sophisticated the controller is, they could potentially send a lot of input and get a lot of feedback through just even 2 wires from a simple coil.

I guess the question comes down to, how do you entirely defeat the system (what parts: carb, ignition, flywheel, or mods to those parts need to be done to make it non auto tune). My initial thought for posting all this was, what if the dumb solenoid wears out (possibly many years down the road), and I can't get a replacement. Like how do you convert a computerized Cummins to a non computerized one, so you can keep running it glitch free when the computer acts up.

 

[DND 9000]

I guess the question comes down to, how do you entirely defeat the system (what parts: carb, ignition, flywheel, or mods to those parts need to be done to make it non auto tune). My initial thought for posting all this was, what if the dumb solenoid wears out (possibly many years down the road), and I can't get a replacement

If I remember right, I think tree monkey did such a conversion in the past on a Ms 462 or 661? But even if it is possible, it is not worth it if you don`t have the parts for it laying around. Much too expensive if you have to buy the parts. As you already stated, you would need at least a flywheel, ignition module, other wires and a carburetor, maybe other things too. There can also be other factors play a roll like different crankcase halves depending on the exact model. I also think that it will take a long time if the spare parts for the C-M models will be NLA.

 

[Ketchup]

Has anyone tried installing a manual carb with the computer carb hanging on the harness?

 

[lehman live edge slab]

Kinda wondering why anyone would want to defeat the mtronic or auto tune. Parts will be available in one form or another for as long as the saw is around and legitimate for use. Only going to be more mtronic/efi saws because of emissions.