You should seriously consider a clear float bowl. On engines capable of
pulling high vacuum WOT often will drain the float bowl if you don't
run a fuel pump. The resultant lean condition isn't good for your
engine!
Bill Jepson

This a very accurate piece of data. Years ago I was having dreadful tuning problems with my first Weber.

We were at Sebring Florida.

A fellow came over with a little gadget he said would explain the problem. It was a small banjo fitting with a vertical clear tube attached. It installs into the side of the Weber float bowl where the brass plug used for draining the bowl is located. We removed the plug and drained the bowl. He installed his gizmo and we fired the engine. The clear tube filled up to replicate the fuel level in the bowl. He revved the engine to 5,000 RPM.

 

The clear tube was empty. At 4,000 RPM it filled nearly full again, and a slow increase to 5,000 RPM emptied it again. A nearly complete carb education in 45 seconds. So, the jets that come in the new carb, designed for a peak RPM of 4,000, will not work well above 4,000. Duh.......................Too lean? Yes I guess

I guess so.

 

Here is an article in VW Trends Magazine about modifying the Weber 48IDF for higher performance use.

Use the forward and back arrows on the page to navigate.

 

Lynn E. Hanover