Xs400 dies with throttle

[terrorshark]

Hopefully someone here can help me with this.

1977 xs400 dies with throttle. Choked it revs no problem.
pilot jet is a 42.5
Main is a 155.
Previous owner put what looks like a separate pilot jet in place of the brass screw sitting above the pilot jet. As well as capped off both vacuum ports on intake boots which I brought back to stock set up with vacuum hose and a cap on the other.
Carbs ultrasonic cleaned.
No clogged jets. Good diaphragms.
synched carbs
Valve clearance is correct. Timing is correct.

I have changed jets up and down with no change in performance. Made brass screws to cap the pilots. No change. Adjusted air fuel screws. No change.
I have no idea why this thing won’t run correctly. Help.

 

[xschris]

Post some pics of the bike. 155 main jet it very large. Those should be 142.5 for a stock 77 bike. Most use 132.5-135. What clip are you on for the jet needle? Should be the third one. Also what are your floats set at? Should be around 26mm without the bowl gasket on. What are you pilot mix screws set at? 3 turn out from a very light seat is a good start. Check to make sure the tips have not broken off into the carb bodies as this is very common for the 77-79 year carbs.

 

[XS4004lyfe]

Go over the carb again and again.
Is your vacuum line from the carb boot to the petcock hooked up?