jeffcat you seem to know those V briggs and I got a question

I have a couple 60 inch mowers one with a P220G (4020) and a zero turn (5820) with a Vanguard 20hp Briggs both Ingersoll. When I hit the tough mowing the onan shines the briggs is a weak sister and loses power immediately.
After I purchased the ZT, (it had set for some time) I repaired the charging system stator and volt reg. I had the flywheel off key was good. I didn't pull the intake but used a rubber cork and my vacuum pump to check for leaks, they pulled down but slowly went back to zero. Set the valves per manual. Compression was good I don't remember how much. Still it was really anemic seemed to pop back thru carb some. It has the the two barrel NIKKI with two different jets.
So I got the next size bigger jet for the large side and moved the existing large jet to the smaller side. There is no fuel solenoid on this. I did replace the twenty dollar o ring /gasket on the bottom of the carb.
Any thoughts appreciated. Thanks Tom
P.S. Oh yeah I reset the mags

Well let us take a gander. It shouldn't pop back trough the carb. I have seen something that can be misleading in this sound you heard. It might be a crackle of exhaust. First I will say that stupid key must be perfect. The washer on the flywheel that is concave gets weak and even with the nut tight the flywheel will still slip. I put a big lock washer on top and then tighten the nut. On one of my Husqvarnas the muffler was too high in the frame. The engine could not exhaust correctly. It would make a funny crackle note now and then in the exhaust. It was partially cutting the exhaust off. I cut a little sideways facing opening in the pipe where it goes into the muffler and added a couple of washers. There is also a little baffle ring collar that acts as a seal into the muffler. If it breaks loose and falls down it can also choke the exhaust. These fixes are after the engine. Let's move back a little. Are you sure the governor is set correctly. I set the ones on my older Kohler engines and one was off. Try down loading the service manual off of Briggs web site. There are PDF files for most everything there. Also you can get a manual disk from sellers on Ebay for your engine. Valves are 4 and 6 from everyone I have talked to. You could have a flukey governor linkage internal of the engine but I have not pulled the bottom off of one of these puppys. See if you can get the service book. Lastly is the carb.. I have rebuilt a couple of Niki double barrel carbs and even checked them with a number set of finger drills used for setting commercial kitchen equipment gas orifices. Kit of drills costs around $135.oo. Both jets were the same size in the two carbs, So I don't know where folks are getting the different size stuff. Just guess all of mine are set up standard. If you look in the parts explosion there is 117-117A-118 and 118A for the jet part numbers. Cannot find what size they are anywhere. Both of my carbs. just work dandy. Now there is no way to fix the jets when they fall out cause you cannot buy the stupid little "O" rings, BUT there is a guy with an advert on ebay with a Kit of the bowl gasket and those two little rings for a few bucks. One funny thing I found is the plastic manifold can develop a leak between the carb body and the manifold flange where it mounts to it. Put a dab of silicone seal between them.
Now as it stands This is everything I can think of and I have posted quite a few pictures on the garden tractor site with explinations of them. I re re read your post and I think things are looking back to a governor problem Orrrr if the linkage IS working correctly then it sounds like a fuel problem and the engine is starving. These twinV engines do have guts But I have seen engines do as you describe. The Niki carbs are a kind of balanced system deal and there are no settings of any kind. I actually saw a twin V that would only run on one cylinder no matter what, till the guy just gave up and bought a new carb. Problems fixed! That may be what you need to do. See if you can talk to a friend with one of these motors and borrow his carb. Put the two machines side by side and swap a couple of parts around and see what they do with the other's parts. The problem should follow the bad part. No kidding, it just might fix it. Could also be a weak fuel pump. Really!
When I have worked on the big commercial machines I fix ,every now and then I have had to have two of them side by side and just swap parts around till you find it. Usually one or two parts and you find the problem. Many times it is a really stupid simple thing that just never occurred to you. Even just a little adjustment being off, or a fluky part.
Get back to me so we can see if we can hash out a fix for you. One last thing. Are you using Hi-Test gas? My 46" Husqvarna with the 21hp engine goes nuts if you put regular in her. Put Hi-Test back in her and everything is happy.
That's all I have. Let us know. Jeffcat

Jeffcat, here is a shot of the nikki carb it does have screw in jets and the part numbers are different. The serial number is at the top of the pic. I haven't taken the time to investigate the governor setting yet. Tom