Author Topic: carb pilot air screws adjustment  (Read 3460 times)


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carb pilot air screws adjustment
« on: June 25, 2015, 07:21:35 AM »
Can someone please advise as to a preliminary setting for the front as well as rear carb pilot air screws,how many turns out from full closed to obtain a good baseline setting,I think as you unscrew the idle mixture gets weaker,as well as turn will richen idle mixture.
Jim ruska


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Re: carb pilot air screws adjustment
« Reply #1 on: June 25, 2015, 02:34:07 PM »
Can't remember off-hand but it should be an easy search.

You have it backwards....  CCW is richer, CW is leaner.



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Re: carb pilot air screws adjustment
« Reply #2 on: June 26, 2015, 03:13:25 AM »
My advice, go for a ride and ride the bike warm. Then let it run and start adjusting yourself. Turn the screw 1/4 turn counterclockwise. Wait about 10-20 seconds and hear if the rpms rise or decrease (or watch the rpms from the tachometer). If they rise turn 1/4 turn more CCW. If they decrease start turning clockwise 1/4 turn at the time. In both cases keep turning until the rpms doesnīt rise anymore. When this point is found (rpms donīt rise anymore when turning) turn 1/8 turn back and you have basic settings done. Do this to both carburetors individually. When you have basic settings for the mixture then adjust the correct idling speed.


After having basic settings done give a full turn on gas handle and then let it go idling. After the settings are ok the bike is back at the idling speed quite quickly. If the motor is near to go off or struggling to stay running turn the mixture screws 1/8 on CW. Then do this again. Usually after one or two times doing this and the bike is running quite nicely.
« Last Edit: June 26, 2015, 03:21:25 AM by b_racuda »

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Re: carb pilot air screws adjustment
« Reply #3 on: June 26, 2015, 04:38:38 AM »

Yamaha don't specify for US models as they are factory set. 
2 1/2 turns is the specified starting point for Euro 82 models, 3 1/2 for the XZ400