Fuel starved?

Bike starts perfectly, idles great, runs strong for a 10 minute drive...then slowly starts to lose power until it stalls completely like its out of fuel. The tank however is full and the fuel line is full as well as the float bowls. New battery. New starter. New plugs. Fresh gas. Persistent problem. What's up with this? Plugs are black and sooty. Oh I forgot, new air filter too. Running too rich? Air starved? Anybody had this issue and resolved?

Not so easy a problem to solve without more information. Have you removed and cleaned the fuel tap, are the airways clear from the vent under the front of the seat all the way to the filler cap? Do you still have the fuel solenoid fitted? How have you routed the fuel line from the tank to the carb?
Whatever your problem is, don’t panic. There is nothing on these bikes that cant be fixed with the help of the guys on this forum.

Check your choke is returning and moving freely.

When she stalls after ten minutes, open filler cap just a touch and listen if air gets sucked in etc.

wirral_biker wrote: Check your choke is returning and moving freely.

When she stalls after ten minutes, open filler cap just a touch and listen if air gets sucked in etc.

Point well made here. If the tank vent is blocked, no air in , no gas out.

Also, there are some electrical issues that come to mind when "things start to heat up". Electrical connections that are slightly loose will build up resistance and cause havok. Bad ignition coils will cause similar issues when they heat up. The ignition pick up coils have been known to cause issues when they heat up.

Bottom line, don't leave out the electrical in your diagnosis.

I know someone else had this exact problem and I can't remember who, but the symptoms were identical. Runs great for 10 minutes and craps out.
Hang in there, it's curable.

Edit- I think I found the link to the previous writ up I had read. Check this out. www.kz1300.com/index.php/forum/carburato...t-again?limitstart=0

I took off the fuel solenoid many years ago and threw it away as per Dave Ewing. The gas line is direct to the fuel rail and fuel is definitely getting there. That's what intrigues me because it acts like fuel starvation although fuel is getting to the carbs. I get fuel coming out the drain on the float bowls. The plugs are sooty so it's running rich, right? I'm wondering about the connection between the air box and the carbs because there is a poor fit there...it never fits tight so air is getting in. But it seems that it's running rich so that suggests not enough air. I took the carbs off during the winter and cleaned the floatbowls which had crap in the bottom and everything looked good. The tank has 2 vent hoses which I haven't ever checked but fuel is definitely coming through the petcock (which I took off last fall to check the filter which was clear of debris). How do I check tank vent hoses?

Have had this problem years ago, the bike will go up to full power then gradually drop in power till nothing (was returning to Derby from London). I would have to then wait 5 mins at the side of the road the carbs would fill again, then I was off again would do a mile and the same thing would happen again (long journey home). It is fuel starvation of some sorts. Check The obvious first no kinks in the fuel line, inline filter if fitted clear, Fuel cap vent not blocked, then fuel tap filter, By pass fuel solenoid stop valve if fitted. If fuel supply is not clear and flowing freely won't take long for those carbs to empty and not keep up with the fuel demand from the engine. Also ensure your fuel hoses are in good condition where they connect to tank carbs etc have known these to have been damaged in the past on other vehicles and a small flap has been created helping to block the fuel supply.