Posted by David K on March 18, 2002 at 19:06:24:
In Reply to: Savage Technical QAuestion # 69 posted by Hal Pollner on March 18, 2002 at 17:57:26:
Hal,
The butterfly only controls air flow. This resulting air flow change creates a vacuum in the diaphragm that you mentioned. The vacuum in the diaphragm causes the needle to lift, out of the needle jet.
There is the idle jet circuit (set by screw driver at the factory) that meters fuel with a closed butterfly. Second there is the diaphragm lifted needle that regulates the fuel at a variable rate to butterfly opening position. And third there is a main jet that regulates the fuel at wide open throttle, when the needle is completely clear of the needle jet.
The white spacer ring is a needle position stop that IS NOT NEEDED FOR PERFORMANCE. It was installed by the factory as an after design, for a leaner mixture burn. It restricts the amount, that the vacuum diaphragm can lift the needle. This means that there is a dead spot, in acceleration and and posible restriction of the main jet supply at full throttle!