No effect when you goose the gas? Dirty (clogged) gas filter, clogged brass filter sock in the bottom of the tank, carb floats/needle valve stuck?  Sounds like a fuel issue to me.

Do you have an electric fuel pump?  If so do you hear it run at startup and then occasionally?

Do you have a vent to fuel tank?  Either a vented cap or a small hose off filler tube.  Try running it with the fuel cap removed.  Could be vent is blocked.

That sounds like a classic clogged fuel filter.

Get it up on jackstands or on a lift at a local mechanic and follow the fuel line from the tank (up front) back to the engine.  The fuel filter could be anywhere along the length.  Once found, replace it with one similar.  While checking, look for any sharp corners in the line that might be crimping it partially shut.

If it is a see-through plastic filter, please do not use another one of those.  Instead, go to a local NAPA store and ask for a NAPA Gold 3031 metal-can fuel filter and use that instead.  Much better filtering and it won't melt under heat and set your car on fire.

You probably won't have to pull the tank (but it is really easy to do, no matter what).  Instead, you can get to the outlet under the tank by pulling the passenger side front wheel to gain access to the underside of the tank.  Drain the tank and then remove the outlet (there will be some gas spilled even if you drained the tank) and check for debris or clogging.  There may be a small screen on the outlet up inside the tank - Or maybe not.   Use teflon tape on the threads when you replace it.

The only other things affecting it might be (a.) a rubber fuel line that has grown mostly shut, (b.) a clog at the carb pilot valve (unlikely, given that it runs for 15 minutes) or (c.) a weak fuel pump (again, unlikely).

Good Hunting.

A temporary fuel pressure gauge T'd into the fuel line in various places will give you some info, not guesses. Try before and after pump, before and after fuel filter. Also, just for the heck of it, try removing the filler cap. Sometimes they go bad and won't let any air in as the fuel level goes down, that could definitely be it.

Points? could be condenser going bad. Electronic ignition module? Could be that going bad as well, also could be the screw that holds the module to the advance plate in the distributor.

90% of fuel problems are ignition problems.

Float/needle valves? Was the float height incorrect? Fuel pressure? 3 to 3.5 psi, no more, no less. 

Like I've said a zillion times before, without putting a gauge on your fuel line, you really don't KNOW what your fuel pressure is. You need to KNOW.

I had a dune buggy that would run a few miles and the engine would mysteriously stop. I would sit on the road side and mess with it and it would finally start up and run perfect then a few miles later the exact same thing would happen. I finally figured out that the fuel tank vent tube was bent and pinched so no air could get into the tank to replace the fuel being sucked out and the engine would then be starved of fuel.. As I sat on the roadside the little bit of air that could get by allowed the tank to fill with air again.  I cleared the kink in the fuel tank vent tube and  all was well. Do you have a vented cap on your fuel tank? Is the tank vent tube clear and open?

Well, after a bunch of web surfing and spec reading, Jim is absolutely right - Don't use any Teflon-based product for sealing threads on fittings for gasoline.  Teflon will slowly dissolve in a gasoline/petroleum environment.  

Bathroom faucet, yes.  Gasoline fittings, no.

Instead, use something like this (they have it at NAPA, too):

Ray Shanahan posted:

I am having a problem with my engine. I have a 1600cc with dual webers and it dies after running for 15 minutes. I have swapped the coil and it still occurs. Any suggestions?

Hi Ray

i am also having problems with my 1600 cc engine thanks to the negligence of my incompetent mechanic.

i also have dual Weber’s. 

Do you know the details of your engine?

is your engine of 1641 cc (100.5 cui) displacement, delivering 67 kW (91 PS, 90 hp) of power.

Tank venting?  I'm a crew coach part time. Our novice coaches would take off all full of piss and vigor. Next thing the eight full of kids would be hammering down river with the coach's launch sitting there -yanking the **** out of the cord. Smiling as I went by "Open the tank vent!" 

When I was a kid my dad had a 24' wood cabin cruiser with a 4 cyl inboard Gray marine engine.  One day the engine died during fishing for blowfish.  The copper 20 (?) gallon gas tank had collapsed (vacuum sucked it near flat) - we discovered mud dabber wasps had filled the tanks air vent out the sided of the boat with red clay.  Poked it clean and fortunately engine restarted.  Weren't any Tow Boats US in Barnegat Bay NJ back then (and hardly any Blowfish now)!   

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