Motorcycle Repair: carb adjustment on Honda Trail 90 (1974), honda ct90, honda trail 90

Question
I need to speed up the idle speed. The carburetor has two adjustment screws on its side. Which screw speeds up the idle and which way do I turn it-in or out? Otherwise it runs just fine. Thanks for your help!!

Answer
Jim, the idle speed screw just screws into the carburetor body and pushes the slide upwards, which increases air flow and idle speed. The other screw is for idle mixture control and is basically only affecting the idle speed mixture and none other.

The idle speed screw is centered on the carburetor slide portion of the carburetor body. The mixture screw is more forward towards the intake manifold.

http://www.cmsnl.com/honda-ct90-trail-90-k4-us_model623/partslist/E++1301.html

Carburetor adjustments are effected by spark timing and valve adjustments. so do those first.

Bill Silver