Topic: Which way to turn the air screws.........

[mmtsquid]

I've heard several different things on here........
77 CB550K - which way do you turn richen up the bike?

[csendker]

'77 550K's should have Keihin type PD's; X46A set-up carbs on them.  If so, they have pilot screws as opposed to air screws.  This means you're adjusting the amount of aerated fuel delivered (as opposed to the amount of air-only in the older models).  Soooooo, that means you turn the screw counter-clockwise ~more fuel~ to enrichen the mix (as opposed to air screws where you turn clockwise ~less air~ to enrichen the mix).

Less convoluted answer: pilot screws are turned counter-clockwise to enrichen the mix.  Factory setting was 2 turns from snug.

[TwoTired]

The PD carbs have Idle Mixture screws.  Turn CCW to richen the mixture.  They mainly provide adjustment for idle throttle positions, and contribute very little above 1/8 to 1/4 throttle settings.

Cheers,

[mmtsquid]

Will making the idle richer help with the cold nature of the bike?

[TwoTired]

Yes to the concept.  But, the IMS screws have very limited range.