Bike stalls after running for 15 minutes or more

Questions here are better with full 'year make model' instead of generic '318'.

A few generic ideas.

1. Check fuel pump pressure.
2. Run injector cleaner through the fuel system 'Extreme Clean' is a good one.
3. Clean the throttle body.
4. Does it have a MAF (mass air flow sensor)?

More ideas here

https://www.google.com/search?q=1989+Dodge+318+stalls+and+surges+when+starting

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There can be many causes:
Loss of fuel pressure, increased back pressure, fuel tank vacuum, loss of ignition pulse,

If you know the brand and model, you can find answers on the WEB or YOUTUBE

Fuel Pump / or Filter

Carbs have a reservoir in the base that will last for a few miles before it is drained. So turning the fuel off doesn't starve the engine immediately. This is normal.

From the sounds of that I would say FIRST get a new battery!
The stalling problem sounds to me like the carb needs to be cleaned!

look at sears parts online

BAD STARTER SWITCH

Sounds like you coil is over heating after running a few minutes. The windings are seperating, then when it sools they make contact again. Try replacing the coil.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

Sounds like a fuel problem. Check for fuel tank vent plugged. Usually in the fuel cap. This problem normally causes the bike to stall but will restart after a few minutes. Usually runs for about five minutes and quits again. Try running with the fuel cap loose but not off.