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450 1970

Dellorto square slide VHB 29.

The needle has three grooves in the top.

A clip goes into one of them to hold it in.

Does the clip go into the top, the middle, or the bottom groove?

Thanks.

SMS
 

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the way the needle works is the following, when you open the gas the needle goes up with the slides and open up the jet though of course it's not open or close because the needle is shaped as a V.

now if you go up on the needle you will release the full jet flow later and if you go down it will be earlier...that mostly effects middle range than top end.

The rule of thumb is do not fuck with the needle, leave it stock position which is usually in the middle and change either the jet or the neddle nozle.

hope this helps

gabe
 

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the way the needle works is the following, when you open the gas the needle goes up with the slides and open up the jet though of course it's not open or close because the needle is shaped as a V.

now if you go up on the needle you will release the full jet flow later and if you go down it will be earlier...that mostly effects middle range than top end.

The rule of thumb is do not fuck with the needle, leave it stock position which is usually in the middle and change either the jet or the neddle nozle.

hope this helps

gabe
With respect Gabe, I must disagree on two points:

#1 Raising the needle enriches the mixture (more and sooner depending on degree of taper). Lowering, the reverse. True, midrange is most effected by the needle with the main jet mostly responsible for full throttle mixture. However they do overlap.

#2 Altering the needle position, along with jet changes, needle size including diameter and taper, slide cut-away, and float height are all key to fine tuning, assumning all else is in shape (engine timing, spark timing, correct spark plug heat range, compression (i.e rings and valves), and fuel quality/age.

Carb tunining only has one cardinal rule: Make only one change at a time. Short of a Dyno, and EGA the objective is to achieve full performance throughout the range with no flat spots (falling performance) and a nice light chocolate brown color on the plug. Too light=too lean and may cause a holed piston, too dark to black=too rich, but you won't do permanent damage.

So the lesson is start rich, check the plug often and replace with clean plugs at each test. A test is a road test with the engine warmed and achieve 3/4 to full rpm (usually 2nd or third gear) then chop the spark, close the throttle and pull the clutch all simotaneously. Take clean plugs, and tools to make ONE CHANGE AT A TIME insearch of the light chocolate.
 
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