Gary_in_NJ
Serious Thumper
Offline
LS650 Cafe Racer
Posts: 2633
Amongst the Twisty Roads
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As a rule of thumb...
Idle to 1/8 (or less) throttle = Pilot Jet / Air Screw Adjustment 1/8 to 3/4 throttle = Needle* 5/8 to WOT = Main
*there are a lot of variables with the needle circuit. Clip position, condition of the needle valve and the tapper of the needle itself all have an effect on this circuit - a circuit that you do 90% of your riding on.
The only way to tune the needle circuit is by feel and performance. Feel and performance include hesitation, lean surging, bogging, burbling - to name a few conditions.
By the way, a spark plug reading is really only valid for WOT operation and a new spark plug must be used. This is an easy test for a bike where the spark plug is easily accessible (like a dirt bike) but a challenge for a bike like the LS650 - and impossible for a fully-faired sport bike. As an alternative to a plug read, I like to get the bike to 5/8 throttle and roll to WOT. I'm looking for a linear transition with no reduction or surge in power delivery. A reduction in power delivery indicates too small of a main jet, while an increase indicates that the needle circuit is too lean.
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