Topic: Carb/running issues on start up....

[CapeCafe]

I have a 76 550K that I have just started for the first time since 1992.  The bike fired right up but I'm having issues keeping it running-

Background-

4-1 MotoGP Werks exhaust
K&N pod filters

Completely rebuilt the carbs-
New main jet - 110
New pilot- 38
New air screw- 1 full turn out
New needle- 3rd notch from top
all new gaskets
used "light synch" method upon re-assembly
I have NOT performed a vac synch yet
Have new points gapped to .012
Have new condensors
Have new spark plugs NGK D7EA
Valves adjusted
confirmed spark to each cylinder
All 4 pipes are getting hot

Problem-

Bike starts right up with full choke but I need to stay on the throttle to keep it running.
Will run smoothly at 2000 rpm but once I let off it dies.
When I take the choke off it dies.
Once warm, it requires close to a full throttle to start again and races right up to 7000 - 8000 rpm but still requires choke.
I've checked each plug and they are not sooted up.  They are a light brown color, but do have a bit of soot present around the edges of the plugs.
Basically running like crap, but no smoke or fluid leaks anywhere.

I'm fully prepared to fiddle with jets and settings for as long as it takes to get the bike running as well as possible.  Right now I really need to simply get it into the right neighborhood so I can at least keep it running as I work methodically through the tuning.  I'd appreciate suggestions on where to start my refinement.  Thanks

[flybox1]

does adjusting your idle set screw help keep it idling?

[Dave Voss]

Have you confirmed that the carb float settings are correct?  I recently refurbished the carbs on my '78 CB550K, and while apart I discovered that all of the floats had been adjusted to the specs for the earlier carbs, and not the later PD carbs which I have, causing the idle jets to be starved for fuel, and requiring the throttle to be held open to keep the engine running.  Before, the engine would not stay running below about 3000 rpm, but now it idles nicely.

[CapeCafe]

I did measure all the floats during reassembly and they were all at 22mm, so I did not do any adjusting.  I have not messed with the idle screw yet.  I did not make any changes to the setting when I took each carb out of the rack and during re-install.  I will give the idle set screw a couple twists to see if it helps get it on idle.  Thanks

[flybox1]

if your idle screw is backed out all the way, there is nothing but your hand on the throttle keeping the slides up and your bike alive.  sound familiar?    use the set screw for this.
after start with choke, to keep the rpm's steady and  to allow it to reach op temp, turn it in a bit to hold at 2500 +/- . rpms will climb as it warms, and you can slowly reduce choke and back out the idle screw to lower rpms.
once up to temp, and you can take the choke fully off, set idle screw so the idle is held @ 1000-1400

[TwoTired]

Describe what lever position you believe is "choke on".

[CapeCafe]

Choke On is "lever up" and the choke is functioning correctly and in synch on all 4 carbs.

[lucky]

You had not started the bike since 1992.
You have 4 into 1 exhaust and POD filters.
You have the needle clip on the third notch from the top.
That is one step LEANER than stock. Stock is 4th notch from the top.

The stock jetting is mains  #100's.
Idle jets #38's.
Slide needle clip position 4th groove from the top.

It will not run even if the tank and filters are clean because it is starved
for fuel.

My recommendations is:
#110 main jets.
Needle clip 4th notch from the top.
#40 idle jets.
mixture screws 1.5 turns open.

If it has any hesitation at all when quickly opening the throttle,
lower the clip on the needle to the 5th notch.


WARNING:
Please do not call me names, tell other members I do not know what I am talking about etc.,.
Either use the information or go onto another post thats all. Your call.

[CapeCafe]

Well, I deserve whatever abuse you wish to bestow, because my problem was lack of fuel...because I did not put enough in the f***** tank! I originally only dropped a quart or so in the tank and put it on reserve thinking I'd have problems and would need to have the tank on and off.  I'm such an idiot.

I just put a couple gallons in, hooked up my tender (cause I ran the new battery down trying to start a dry bike) and it fired right up and was off the choke and idling smoothly at @ 1,200 rpm.
 
Thanks for your recommended settings Lucky. It seems to have good throttle response now, but my only reference are my Ducs and the 12r. The rpms were hesitant to drop below 2,000 rpm after a couple throttle snaps into the 5-6,000 rpm range.  I'll get it out on the road and see how she does under load and then do a couple plugs chops and start working to get her dialed in.

Again, sorry to waste your time.  I'm sure I'll be back looking for advice as I start to get into the tuning.  Thanks!

[lucky]

The clue for you was, "It will not run even if the tank and filters are clean because it is starved for fuel." So you looked in the tank didn't you?


 Smart man and good reader.


WARNING:
Please do not call me names, tell other members I do not know what I am talking about etc.,.
Either use the information or go onto another post thats all. Your call.