My VL250 is dying after i switch to reserve, it idles ok but as soon as i open thr throttle in gear it dies. this problem continues after i refill the tank and switch back to main tank.

There is throttle plate adjustment and idle air mixture adjustment x2 so 3 items to adjust.If the carb is clean and you have NO vacuum leaks the engine should run fine.One trick for a better idle is to run full vacuum at idle speed on the dist vac advance if you have a vac advance rather than a ported vacuum which applies vac only at open throttle.

Start off by cleaning carbs,sounds like idle jets are blocked

are there any codes ? sounds like a bad throttle position sensor and or a idle air control valve

More likely a fuel problem. Tap the choke when you put it in gear and see if it picks up. If so your idle mix is to low or you throttle link is picking up to soon.

take off the muffler and try it if ok open the muffler and clean the carbon off the screen

will it start right back up after it dies? you could use a small screwdriver and turn the idle screw in a little to raise the idle speed that should fix it.

Quickly check for any manifold leaks and in the vacuum tubes and pipes that go into it. Next check out the Idle Air Control valve on your throttle body. This device has an electrical supply that is fed by the ECU when the the engine is at idle. The IAC opens and bleeds a regulated amount of air past the closed throttle plate to allow the engine to keep running. However if the ports, that allow the air past, become blocked or the valve becomes gummed closed then the engine will idle OK until there is a power demand made such engaging the power steering or shifting into gear. You will need to remove the air ducting to the throttle body. Take some carburettor choke cleaner and a cloth and spray in the inlet port in the interior wall of the throttle body, lift the throttle plate and spray in the exit port. Spray, brush and wipe until clean. Disconnect the IAC and unbolt it. Spray and wipe the bullet shaped valve until like new. Remount the IAC, reconnect the connector and reinstall the air ducting. That should fix it

Sounds like you have a dirty throttle body. This truck has whats called "drive by wire". There are no throttle cables. If you remove the air intake tube you can carefully clean with some carb cleaner and a rag. Reinstall the tube and let it idle for a few minutes so the computer can relearn the base idle. If this does not work you may have a defective throttle body.

first thing i would check is clutch freeplay, make clutch adjustment if necessary. if that doesn't work you might have a bad clutch or neutral switch.

idle air control valve Check idle air control valve on throttle body. Mine had similer problems. A quick fix to get you going should be just unplug and remove spray w/ cleaner to get carbon off spring and cone shaft, reinstall. remember, this is just temporary. If cleaning helped, buy a new one soon. JMO