Help 1980 Yamaha xs400SG Bike will not idle

[HoughMade]

You cannot use the throttle cable to adjust idle. It is not stable and the cable needs free play. Take a good look between the carbs. Where the threaded end of the idle air screw comes through the plate in screws into, the threaded end should be pushing on a metal lever that is connected to the butterfly shaft. Screwing in the idle air screw far enough will push on that lever to open the butterflies far enough. It will if all the parts are there. Keep screwing it in until idle starts to rise.

Also, I don't know what you mean by "Set pilot jets to 3 turns from tightness" the pilot jets are in the float bowl in a smaller tube next to the main jet tube and there should be a screw or plug in the smaller tube. Take that out, and the idle jet is screwed into the tube. It needs to be tight.

The idle mixture screws as in the pictures above under the plastic caps are the only thing that should be 3 turns out (give or take).

 

[jlearning1]

Thanks Houghmade for helping me out. In your 2nd paragraph on the last line did you mean the pilot jet is screwed into the tube, and the pilot jets needed to be tight all the way down? So let me make sure I understand you. The idle mixture screws are the only screws that requires an adjustment in the Carb other than the floats height adjustment?

Thanks Again

 

[jlearning1]

Anyone have any suggestions on this PLEASE

 

[HoughMade]

Thanks Houghmade for helping me out. In your 2nd paragraph on the last line did you mean the pilot jet is screwed into the tube, and the pilot jets needed to be tight all the way down? So let me make sure I understand you. The idle mixture screws are the only screws that requires an adjustment in the Carb other than the floats height adjustment?

Thanks Again

Set the floats, adjust the idle mixture screws, balance the carbs with the screw on the connection between the throttle butterflies and adjust the idle with the idle air screw. No other adjustments on these.