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Put a new carb on to get it running (its's been worked on before by someone else) and it does, but only at idle speed. Slight extra tension on the governor spring gets it going, but the spring looks fine and I'm wary of just crimping it as a workaround. The parts diagram for it shows 2 governor springs, and A and a B and it doesn't say which one I need or both. I've attached a picture with the spring off so you can see its condition. I have an air vane spring ordered, btw.

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Edit: Just found how to ask B&S about the springs. Not convinced that's it.

Your governor spring looks fine, you would not replace it. Air vane spring is toast, Briggs part number 790849. After you get everything back together start the mower and if it only idles bend the tab (on the right side of your picture, looks like a T on it's side) where the governor spring attaches out and the engine should increase in speed.

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Oh, well...

Air vane spring made a difference, now I have surging. Bending the spring post wouldn't go far enough.

When I hold the throttle open at any speed, it runs a bit rough. New plug. Flywheel key is good. Timing?

Time to clean the carb and install a new float needle and seat. Part number 398188. Here is the procedure I use.

Needle and seat replacement

Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.

I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.

With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. *Next check to make sure that the float does not have any liquid in it. *If it does, replace. *If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.

PS: *On the side of some Tecumseh carbs you will find a plastic cover. *Under this cover will be an idle jet. *Remove it and check to see that the jet is open both horizontally and vertically. *You should be able to push the old float needle wire through the vertical opening.

Rivets said:

Time to clean the carb and install a new float needle and seat.

Click to expand...

Forgot to mention the carb is brand new

I have found that most surging problems are caused by a lean mixture. I would start by pulling the carb and checking to see if the float is level or high. I like to set them low, as I describe in the procedure. Yours wouldn't be the first that I've seen set incorrectly. If you feel thecarb is right and the linages are correct, then I would check to see if the governor is set properly.

Just for the hell of it, take a look at the intake tube (manifold) to be sure it isnt cracked.

Get a triger pack NOT A SPRAY CAN of Wd 40 or similar.
With the mower surging spray it liberally all around the area between the carb & the engine.
If you have an air leak it will be obvious.

Seemed like the choke wasn't opening fully so I popped the cover. Yikes, what's going on here?


Edit: Removed that stuff and the choke opens fully. Runs smoothly but still slow. Massaged the spring a bit and I'm now in the right speed range but still have surging. Damn, thought that was it.

Edit2: My son said that was his work and that helped with the surging when he had it. It seems unlikely 2 carbs would do the same thing. Can't see another place for an air leak.

Bod said:

Just for the hell of it, take a look at the intake tube (manifold) to be sure it isnt cracked.

Click to expand...

Manifold and o-ring are good.

Did you check the timing/flywheel key?
Since the carb is new, what about the fuel line/filter? (if there's a filter)
Also check the gas cap condition.

Have you check to see if the governor is set properly?

Rivets said:

Have you check to see if the governor is set properly?

Click to expand...

From what I've read, that's done solely by spring tension and I have the engines revs in the ballpark.

Grassbandit said:

Did you check the timing/flywheel key?
Since the carb is new, what about the fuel line/filter? (if there's a filter)
Also check the gas cap condition.

Click to expand...

Flywheel key is good
No fuel filter
Surges with the cap off

Governed top speed is set by RPM's, but the governor itself must be set mechanically. Please read this manual on how to set the governor, section five.

https://doc-04-5o-docs.googleuserco...253/*/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00?e=download

Rivets said:

Governed top speed is set by RPM's, but the governor itself must be set mechanically. Please read this manual on how to set the governor, section five.

https://doc-04-5o-docs.googleuserco...253/*/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00?e=download

Click to expand...

"Top No Load RPM is changed on these engines by
changing to governor spring. " pg 24

I'm not going to argue with you, but I will tell anyone else who reads this post that you must mechanically set the governor before setting the RPM's. Good luck, I'm out of here.

Rivets said:

I'm not going to argue with you, but I will tell anyone else who reads this post that you must mechanically set the governor before setting the RPM's. Good luck, I'm out of here.

Click to expand...

Didn't mean to offend you. I traced the actuating arm back to the engine and looked for set screws on the carb mounting plate, but found zilch. Many other engines do have adjustments, I just don't see one for my engine. Can you show me where it is?

Try reading page 22.

Rivets said:

Try reading page 22.

Click to expand...

I read Replace Governor Shaft Bushing for a mechanical linkage governor on that page. I have a pneumatic type whose adjustment is also here under Setting Top No-Load Speed:

Adjusting The Governor