Hey gang, just wanted to beg for your thoughts on my latest issue!
'75 2.0 dual Weber 40's.
Was on the highway the other day and the engine suddenly got much louder and I began losing power. (I was doing about 65 - 3k rpms 5th gear) I dropped down to 4th, and the issue persisted. Got off the highway and pulled into a parking lot, fiddled with the carbs a bit, and got it running what I thought was normally again. Within a couple minutes of returning to the highway, the problem returned. Same thing, got off, tweaked the carbs again, and this time I was good until I got where I was going. On the way home, I avoided highway speeds, and all seemed ok to get her home. Took her out a couple days later on city streets and had the problem the whole time. The loud engine noise is no longer present, btw. Idle would drop to almost nothing, in fact at lights, I had to keep pumping the gas pedal to keep from stalling. She's been parked now for over a week, and when I have to switch sides of the street for parking, sometimes she behaves and starts up normally, other times it's a battle, and I have to keep pumping the gas to keep her alive until she "catches" and idles normally so I can move her. I don't know where to start looking for the problem. I'm thinking carbs are way out of whack, could also be a fuel supply issue, sticky valve, or maybe an electrical short? The thing that gets me is that it seems to be an intermittent issue. Intermittency seems to me to rule out the carbs unless it's a float sticking. Having to pump the gas tells me that it isn't likely electrical. If there's a fuel line pinched, it'd stay pinched. Scratching head...

Sounds like there might be something in the tank or maybe the fuel filter is plugged. How old is the fuel pump? Or maybe a loose connection. Also check the gas line from the tank back.

Put a pressure gauge onthe line to check pressure.

Pump is new, CB performance rotary 3.5#. Tank is clean, new sock installed last summer.
Just replaced the line from the pump to the stainless end (going into tunnel) in the tank area. I will look at both filters, the one that came with the pump and is just ahead of it in stream, and also the one in the engine compartment. I do need to re-sync the carbs too, but I can't see where those being out of whack would be intermittent. I'll report back tomorrow.

Ok, got it licked. In the course of driving, the nut securing the fuel pump had loosened just enough to allow the pump to wiggle its way about an inch towards the passenger side. (It's installed underneath the tank, not in the bubble where it should be...) As a result, the feed hose coming from the tank was bent a little too much, allowing some fuel to pass but not enough. So... The trickle I could see coming into the filter in the engine compartment was enough to handle idling (most of the time) as well as a couple of revs twisting the linkage bar, but when on the street, it would quickly suck the filter's reservoir dry, then start to refill it when stopped at a sign or light. Always something stupid, isn't it?

Funny thing is... On my test run to the (hand) car wash, after washing the car, the gas gauge stopped working! Fuse looks fine.