I have a Murray Wide Body garden tractor with an old Briggs I/C Twin II. It starts instantly and purrs like a kitten, It'll run 5-10 minutes, then seem to run out of power and dies. Pull the choke and it re-starts immediately. The mower had sat outside for 6-7 years so the gas tank has been cleaned, new fuel line, filter and carb rebuild. The tin was pulled and all the cooling fins were cleaned. Any ideas on what I missed?

Sounds like it is not getting enough fuel. I would recheck the float to see if it is dropping freely and that the new pump is working properly. Please post engine numbers.

Its becoming obvious that I messed up on the carb and need to clean it again. I have to play with the chokd to get it to run and the idle jet screw has no effect at all. The vac tube to the fuel pump is tight and the pules are strong. All the same, the pump will get special attention this time. It has all new parts, but this doesn't mean they stayed right while I was reassembling it. I was originally gonna sell this, but it has tooooo many rattles, squeeks and shakes for me to trust anybody else with it. 7 years ago, when my cousin brought it home, there were only a couple of things wrong with it, all belt related. It sat outside all that time, unused. Most of the springs rusted away and now there seems to be a lot of "crud" built up on the drive pulleys to cause it to make lots of racket. The clutch idler is about the only clean pulley and I made sure it was tight. Still doesn't smoke and except for a little exhaust leakage, it's okay. It's only a '94 so it surely has more useful life in it.

Run time of 10 - 15 minutes is fairly common for those that have a gas cap vent plugged. It doesn't cost much to check that.

Ok, so I tried the gas cap. It still died. Took the carb off and sprayed it with Berryman's then washed it with hot soapy water (something you nearly have to do with Berrymans, with Gumout, not so much). Blew it out with about 30 lb air. After making sure the float was level, I put it back together. Runs like a champ now. The only problems now are getting the exhaust straightened out and cleaning a seriously fouled, brand-new plug.

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I moved your thread to the Small Engine & Mower Repair Forum.