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Old 01-23-2013, 12:41 PM   #1596
Pigford's Avatar
Joined: Sep 2009
Location: North Dorset, UK
Oddometer: 994
Pjensen641 - thats interesting - and I agree that either have "waisted" needles to increase fuel at a set needle/throttle opening to make a bit richer..... or a larger main jet.

As you rightly say, a DYNO run is the only 100% way to evaluate the A/F ratio to ensure you're not running lean at WOT (Wide Open Throttle), which could spell disaster if the main jets are too small !!!

One point with the pilot jet and the pilot screw.... it's generally accepted that once the screw is open over about 3 or 4 turns, the screw has zero effect as the passageway is full open..... so if you start winding it further the next size pilot jet is needed.

NOTE: The PILOT SCREW is in fact a method of controlling FUEL flow - not AIR (as in AIR SCREW)..... this is usually distinguished by the fact that the scew is the ENIGINE side of the carb - not the AIR BOX (intake) side So if the screw needs to be wound out, it's to make the part throttle circuit RICHER.

Due to the sh*te weather here (UK) I haven't had chance to go for a decent run to do a plug-chop, so can't comment to specifically yet.
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