TOPIC:

Definitely interesting.

When you cleaned out the new tap, was anything done with the spring behind the diaphragm? If it was replaced using some kind of standard kit maybe it could be too stiff? You mentioned that the flow was improved after adding more vacuum lines. Could it be further improved by removing a coil or two from that spring?

Just me spitballing again lol.

The other item that comes to mind is the tank vent.

You could have a vacuum forming in the tank and restricting fuel flow at higher RPM.

Last year, I was troubleshooting the same problem with my KZ1000. Bike kept running into fuel starvation, just like your bike. I kept thinking it was the fuel tap, when in fact my fuel cap had a paper gasket installed wrong by 90deg. (I won't tell who did that.)

I realize the fuel caps between the two bikes are not the same but vacuum is vacuum and I would wonder about tank venting at this stage. Especially if you have tested the vac. tap.

T.

Yep,

You are on the money with that one too...........but the vent was completely cleaned out (with an old inner throttle cable) from one end to the other after I got my tank back from paint 3 weeks ago. I also replaced the little seal that sits in the hinge mechanism in the fuel flap.
Its clear as a whistle !!

I suffered from that issue on a 1300 many years ago so always check it.

Its not looking good for this GPZ900 Fuel Tap !!

Pete F

No eBay APP ID and/or Cert ID defined in Kunena configurationI wonder if we should bump it up to a GPZ1100 tap...

Might not be as easy to find, but not impossible. Here's one:

There is not an inherent design fault with the fuel tap- I've done 100 mph on my bike many times over the years with no fuel starvation like you are experiencing. For a few years I used an electric fuel pump also and at the end of the riding season set the tap on prime and using the pump would drain all the fuel from the tank and the tap had no trouble flowing enough fuel to keep the pump full.

How about disconnecting the fuel line from carbs , tap connected to fuel tank, tap in prime position and eye ball fuel flow into a container - to get some idea whether tap and fuel line are carrying enough volume.

What happens when you rev it up thru the gears at low speed - in other words does it starve at 7000 rpm in third gear ?

Pete.
what size are the holes in the body of the tap ?
from memory they are only 5mm pos 6mm, this could create fuel starvation.

Ian