1985 honda bf100

[samcats]

Have this 1985 honda want run off main tank. Last 2 times out it ran for 5 min then quit then won't start. Does the diaphragm in the pump get weak where it won't suck fuel or does the ball create a siphon it did run òff the main tank earlier

 Put a new carb on ìt. Should I go back to the 3 gal tank

[chinook35]

Sounds like it’s not vented. I worked for Honda many years ago. I had a 7.5 that acted the same. When I forgot to vent the tank. Will it start ( or keep running ) when you squeeze the primer bulb ?  Also make sure you have a shutoff valve between your kicker and main motor or you will just suck air   If it runs for 5 minutes it’s not the pump diaphragm but it’s easy to replace if you want to try it 

Edited September 23 by chinook35

[sherman brown]

I would say the fuel line from the main tank is bad and the inner lining is collapsing stopping the fuel flow.