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How to Confirm Your Pilot Circuit Setting


Eddie Sisneros

It seems like the most common jetting issue that comes up are pilot circuit related. The following is a sure-fire method to choose the needed changes:

With the bike warm and idling, turn the fuel screw in unit the idle drops/misses. Then back out until the idle peaks/smooths. This should happen between 1 and 2.5 turns on an Keihin FCR carb and 1 and 3 turns on a CV.

If you end up at less than 1 turn, you'll need a smaller pilot jet.more than 2.5 (or 3 turns on a CV) you need a bigger pilot jet.

Choose the appropriate size and re-test.

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If you have a hot start circuit on the carb, you can test your pilot screw setting quickly by:

 

On a warmed up motor at idle:

 

1. Pull the hot start *slightly* and you should get a rise in rpms. Pull it more and the engine should die.

2. Pull out the choke and the engine should die.

 

If you can do the above, then your just slightly rich on the circuit.  This is a good spot check if you ride at different altitudes and don't want to go through the adjustment procedure.

 

This also assumes that you've already dialed in your pilot circuit.

 

Jim.

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