Topic: Getting Better at this Carb Thing

[drillzzz]

Thanks to everyone for their help on previous posts. I have a 1978 cb750k I bought it with pods and large main jets and put that stuff back to stock.

Theres a twist please keep reading. I am able to start the bike with the choke fully engaged which only brings her to about 1200 rpms. If I disengage the chocke she dies out slowly. Additionally, when I ride the bike with the choke fully engaged to no choke (when she warms up about 7 minutes) she idles real strong and I can kick the throttle with no apparent power loss. I set the pilot screws and fuel/air screw to manufactures settings with no luck with the idle deal on a cold start. Heres the twist. When I adjusted the pilot screws I noticed that the pilot screw on carb number four can be screwed in way way further than the rest with no kind of resistance... does that indicate no spring? Also two of the pilot screws had fuel dripping from them... I am no wizard at this carb stuff (yet  ) but this would def play a great deal on my idle right? Any suggestions/ advice would be awesome. Thanks everyone.

[Spanner 1]

There is a tiny O-ring in the idle fuel mix seat. So it's o-ring, spring and needle. My guess is your missing some of the o-rings as they seal fuel from seeping out at the needle and air from 'seeping' in to the fuel metering...... here's the twist; carb rebuild kit needed 

[SOHC Digger]

Spanner 1 is right about the o-ring.  They are so small and easy to overlook.  The fact that number four is going further that the rest is not an indication of a spring missing.  The screw does not bottom out against the spring, but rather the carb body.  You may have a bad screw or body.  Check how far the screws protrude into the carb throat when bottomed out.  The tips should only stick up about a 16th of an inch or so.  If #4 goes much further, switch the screw with another one and determine if it is your screw or carb body.

Either way, I have spares of both.  If you need them, message me and let me know.

Good luck!

[drillzzz]

Thanks for the help guys.

SOHC... I will have to take the air box off and check. Would it be better with the carbs on or taken off? A bit more info that might get a faster diagnosis is that I can screw the pilot screw in so far that it can't be seen from a side view. Yeah I know sounds crazy. Newbee question... Carb body is essentially the meat and bones of the carb and not just a changable component right?

[bollingball]

Take the screw out and see if the tip is broken off.

[Duanob]

I had the same symptom on my 550K. Start and run with the choke closed but not open. It turned out to be bad and broken o-rings between the intakes and the head. And a stripped out vacuum port screw on the intake runner. Either way it sounds like a vacuum leak somewhere.

[SOHC Digger]

SOHC... I will have to take the air box off and check. Would it be better with the carbs on or taken off? A bit more info that might get a faster diagnosis is that I can screw the pilot screw in so far that it can't be seen from a side view. Yeah I know sounds crazy. Newbee question... Carb body is essentially the meat and bones of the carb and not just a changable component right?

Carb body is the meat and bones that houses everything else.  Take a few of your screws out, like bollingball suggests and compare them.  Be careful not to lose the o-ring, washer, or spring for each screw!