Vanguard V-Twin Briggs problem - reaching the end of my rope
I have a 20 hp Vanguard V-Twin (model 358777) attached to a Simplicity Z-turn. I've had it about 8 years. I've had this thing in the shop now twice (to the tune of nearly $500) and still no luck.
Normally, right after it's been worked on at the shop it runs fine, allowing me to mow my 2-3 acre lawn... once or a little more. But then it starts acting up. It will run along fine, then start losing rpm. When I cut off the deck and choke it it will start back up running; it might run for awhile but then with the deck running, it'll cut out again. This last time after it was "fixed" it ran for awhile but now just starts up... then cuts out completely, choke or no choke.
Here's what I've done:
- Replaced the fuel intake line from the gas tank
- Replaced the fuel filter
- Replaced the fuel pump
- Checked that all the lines are clear (and blown back into the tank to make sure there wasn't any clog)
- Cleaned the carburetor (dealer)
- The dealer also cleaned out some valve in the fuel line that had clogged with rust - can't recall the name offhand.
- I also just ran a clear fuel line directly from the tank to the inlet on the fuel pump and started it (with starter fluid) just to make sure gas was running from the tank to the pump.
- Loosened the gas cap to make sure there wasn't a vacuum (it's a pretty new cap).
At this point, I don't know what else to do. Can anyone help? Thanks in advance; I'm about ready to chuck this and just pay someone else to mow my lawn!