1976 carbs too lean. ??

[dingdong]

So after rebuild 12 years ago and the bike running great since then she has developed a problem. The first symptom was stumbling at and around 2k to 2.5k rpm after riding about a mile. Thought I might as well pull the carbs to do a cleaning. Total disassembly.

Before and after

I found no dirt or deposits anywhere even in the float valve screens. Clean as could be and floats set exact. However the plugs (all four) are white now. Way too lean. Pulled the carbs again because I failed to check the slow jets below the rubber plug inside the tower. The rubber was disintegrating and had the jets clogged. Back together with new rubber plugs and now she runs strong with no more stumbling. However it is running very lean. To the point that the engine comes up to "fan on" temps while riding much to fast.... Fuel filter clean. Gas cap clear. Checked fuel pump and it is fine as far as volume is concerned. Don't have a gauge to check the pressure. Any ideas what could cause a lean condition on all four cylinders. And this happened from one ride to the next. I know I am overlooking something simple but.........

[kndw]

Did maybe ignition timing go off, or is there a hole in the air filter?

[dingdong]

Turned out to be the fuel pump. I guess it just couldn't keep up with demand therefore all 4 cylinders ran lean but with no stumbling like usually happens with a faulty fuel pump.

[Fred Camper]

Good to know. Diaphragm pumps can tear and loose pumping so sounds like that happened. Many seem to move to an electric pump to get faster starting so perhaps it is time for an upgrade?

[dingdong]

Installing electric pump now. Thats how I tested to determine if old pump was decective.