Topic: Choke/Fast Idle mod

[hapsh]

What model CB550/750 started using a fast idle adjustment with the Choke?  My CB has a 76 550 engine and carbs that I was wondering about modifying to have a fast idle adjustment.  I normally have to give my idle thumb screw a half turn on cold mornings so that the bike will idle better under choke until warm.  Then after I am riding I have to readjust it back down when warm.  It works OK the way it is, however it sure would be nice not to have to tweak the idle speed every time I start the bike when cold.  I am hoping that I can look at some of the later carb designs and adapt mine to work sort of the same.

[TwoTired]

The 77-78 Cb550K models had the fast idle cam coupled to the choke, as well as a bar mounted actuation knob.

Alternately, you can replace the throttle side control module with one from a 74 K model (and earlier 500s).  These have a thumb screw under the control to apply friction to the throttle that will hold it in place during warm up.

However, I seldom use it.  The main idle knob is set for warmed up idle position.  I suit up, jump on, and ride away with the choke on (partial) and just hold the throttle open with my hand while driving. I don't drive at idle anyway.  The choke gets turned off gradually while it warms and while riding.  When it's warm in a few blocks, it idles just fine.

Cheers,

[hapsh]

It will probably be fine as it gets warmer.  As it is now I have been riding all through the winter (20 degrees and lower) and I usually have my bike warming up as I get the last of my gear on.

[hapsh]

I just got an idea that I could do the same thing with one of those cruise control thingies, maybe I will do that next winter.  As for right now I tried your idea of starting the bike after I was fully geared up and took off within 20 seconds of starting the bike.  By the time I was riding for 7 minutes it was idling on its own.  I will probably save a bit of gas mileage by not warming up the bike too.

[gerhed]

I have fast idle (when choked) on my Mikuni setup.
I think it's a problem though when starting from cold and
you are immediately at 5000 rpm !