Best pic of governor linkage.

Below is the link for an online service manual. Page 57 has a pic. Hopefully even the right one!

Here is a link that might be useful: manual

See attached photo. Picture of my 422707.
I believe the spring indicated by the yellow X is your mystery spring.

And one more. This one from below looking up.

Thanks for the input and the manual. It should help reduce the calls for help later when I go to set the idle and governor.

My pics weren't the best so they don't show the detail needed but the spring you suggest (Yellow X) is there as is the larger governor spring on the back of the governor unit (Red X). That's what's got me stymied. My mystery spring is a longer but less strong version of Yellow X spring. Very little tension.

At work now. Will repost better pics later today.
Thanks again for the assist.

Well, I saw that the mystery spring did appear to be made of smaller diameter wire than the spring on my engine.
Everything about the 422700 engines in the Briggs parts manual shows there to be only two springs used in the governor to carb linkage.
Your description of this project being "inherited" in basket condition has me wondering if the spring you found may have come from an unrelated source and was simply tossed into the mix by mistake sometime before it all came to you.
Many Briggs (and some others) engines use a light tension spring in conjunction with the throttle linkage to dampen, or buffer, the free play in the pivot points of the throttle linkage members which can lead to "hunting" by the governor.
Typically, those springs have a short coil section in the center of the overall spring, but have very long reaching straight wires that end with the spring hooks.
I have included a photo of a Vanguard V Twin to illustrate that point, but I have never seen any buffer springs used on the Opp Twins.

Excellent Photos, Mownie.

Walt Conner

After looking thru the manual several times figured it might be a backlash spring but doesn't seem to fit anywhere so am moving on.

Tried to adjust mix, idle and governor. Governor seems right. Setting idle though engine will not get down to 1300 RPMS without stalling. I did not rebuild carb. probably ought to, right?
Only other obvious problem is the throttle cable does not move the 1-3/8 inches manual says it has to. The lever is limiting the travel. Quersiton: Should I set cable so the max is reached or so the low idle is reached. Can't get both.

The low idle point of operation is accomplished by the pilot, or idle jets in the carb. The fact that you can't get the RPM down without stalling probably means the pilot fuel jet is clogged.
A good carb cleaning including blow all passages out with compressed air should clear that up.
Regarding the range of travel afforded by the throttle cable. If your throttle cable (disconnected from carb) does not give the 1-3/8" range of travel, the problem lies in the cable control structure on the dash. If the cable control is a lever type handle, there might be some wear in the handle pivot that is eating up some of the cable motion, OR........you may be looking at a case where the dash control unit is not compatible with the requirements of the engine, as you said this was a "swapped out" engine project. So, if the dash control is not configured to provide the range of motion require in the cable for this engine, you will need to replace the dash control with one that does give the required range of travel.
You are not going to set the low idle speed by adjusting the position of the throttle cable.
There is an "idle stop screw" adjustment that permits adjusting how much the throttle plate is allowed to close when the governor moves the throttle linkage toward the closed position.

Mownie, thanks for the info.

Idle stop screw: check.

Throttle cable: I was using imprecise wording. If I use the existing cable and lever I can set the cable so the swivel (see pic from manual) will hit one or the other stop. It will have 80-90% of the travel, jsut not all of it. I know the lever is the limiting factor but if I can't (or don't) replace it is it better to adjust set the cable so the swivel will hit the full open setting or the low setting ?

I really appreciate your help.

If I had to choose, I would opt for adjusting so it could attain the higher RPM range.
It is pretty useless (to me) to insist on a working engine being able to to do a slow idle.
All work needs to be done at wide open throttle/high RPM (or very close to that) so that the engine is making its rated power, and so that the engine cooling fan is spinning fast to get rid of the heat.
Trying to slow down the engine to have a slow ground speed is not the right way to do it. The correct way to choose a slow ground speed is to select a lower ratio in the transmission.
If you run these engines at low RPM while they are doing strenuous work, the engine will heat up.......because the fan is not spinning fast enough to carry away the heat being generated.

The engine will still be "stoppable" by cutting off the key switch even if it will not idle slow, but you can't do much work if the engine can't reach its max governed RPM range.

Mownie,

Roger all.

Carb kit due today. Will update sometime thsi weekend if I have a chance. Again, thank you fo rthe assist. Much appreciated.

Carb kit installed. Fixed hesitaton issue and some minor leakage. Still a touch rough. Might be my expectation are too high.
Discovered a charing issue though. Battery dead so now moving on to alternator, regulator, etc. Suspect stator might be bad. Regulator, wiring, and battery are new. Not much left .. flywheel and stator.

Hey. Did you ever figure out a solution to the random spring? I have the exact same engine and the exact same spring not attached to it! I disassembled this engine about 1.5 years ago and like usual just bagged all the parts up *knowing* I could just stick em back together later. I only pulled the intake and carb, and not the governor. So, I'm think this spring links between the two because the other two governor springs are right where I left them. This must be some kind of damper spring to keep the throttle plate from bouncing at idle (maybe on or near the linkage connecting the governor to the carb/intake), but I can't for the life of me remember where it went or figure it out. Let me know if you ever sorted it please...