wind vane governor

[295 tramp]

Could someone explain a wind vane governor?
My 07 stihl has a wind vane governor. Now the way I'm thinking if I move the spring forward it puts more tension on the flap, which at a higher rpm moves the choke lever to slow it down. I have the high screw out several turns and when it goes to Wot it tries to choke it down.?Do I need to richen it up more or what.
Thanks

 

[hotshot]

Are you sure that your air vane linkage is attached to the choke lever?, and not the throttle lever?

Normally, they are attached to the throttle linkage, and designed to limit the engine's top RPM.
The IPL shows that throttle linkage has a bell crank on both ends...

The high speed mixture screw is for adjusting the air/fuel mix, an altogether different issue. Adjust
that screw until the saw exhaust sound just "cleans up in the cut", or stops 4-stroking when buried
in the wood.

An air governor slows an engine down by the amount of air blowing against the flap.
When the air vane is blown "wide open", the saw throttle is moved towards closed or idle position.

Therefore, the more tension you put on the flap (to keep the flap from moving towards "wide open"),
the more air it takes to close or reduced the saws RPMs. Added spring tension will usually increase the top
RPM setting by preventing the flap from being blown wide open.

Here's an IPL link in post #5, but you really need the service manual for the correct governor
linkage from vane to throttle arm hook up.

http://www.arboristsite.com/community/threads/stihl-07-ipl.224799/

 

[Guido Salvage]

My only experience is on steam engines...

 

[HarleyT]

Actually, I worked on one, the air vane was hooked up to the choke.

 

[XSKIER]

The air vane is hooked to the choke on an 08, likely the 07 is similar. Best to tune the H screw while in the cut. On that old dog, too rich is just fine.

 

[HarleyT]

Yeah, one richens up the mix to slow the saw down anyway, that way just does it with more emphasis......

 

[HuskStihl]

I'm going to have to move this to the political forum......

 

[295 tramp]

Well the air vane problem will have to wait.
Now I can't get it started, I cleaned carb twice, looked a fuel filter, check fire, it's getting fuel. I changed to another plug and got it to backfire. I checked flywheel to see if it jumped time, checked points.
It has a good blue spark. I don't know what's wrong.

 

[bikemike]

Oh yes toro and briggs n scrap iron and tecumseh were big on the wind vein or air governor. They are very slow reacting to a fast rpm drop unlike centrifugal governors. The wind governor was a very cheap way to govern and engine and they run off spring pressure and wind speed. If rpm is too low spring is shot or stretched. If yohr rpm is real iratic then richen it up more and if it is slow to gain rpm back then you could be too rich loading up ur engine

 

[Moparmyway]

I have seen both ......... wind vane on choke and wind vane on throttle.
Lawn Boy used the vane as throttle governor
Briggs and Tecumseh used the vane as choke pull off in combination with a bi-metallic coil so the choke wont set when the motor is warm

 

[blsnelling]

It's hooked to the choke. Same thing on the 070/090 as well. The stiffer the spring is set, the more RPMs it takes to over come the spring and activate the choke. It's nothing more than a rev limiter. My advice is to disable it, then tune the saw in the cut. Then re-activate the governor if you choose.

 

[HarleyT]

Yeah, that was what the discussion was about. The air vane is hooked to the choke, and not the throttle, like the rest of the air cooled world.......

 

[295 tramp]

thanks fellows for all the input.

 

[Deets066]

I trimmed a little off the flap on my 090, so it wouldn't catch as much air