Topic: Its alive but dying! Barn find engine (on stand) dies after about 10 second idle

[dramabean]

Hi All,

I bought a barn find 1977 CB550 off a guy here in Los Angeles. Bike had clearly not ran since last plates 91' (before I was born  ) and was stored outside. After about 6 months of work, donor parts, a lot of blood,  I have her up and running with pops and bangs on my engine stand. I have installed a few new parts listed below, hooked up the electrical wiring harness so that I can turn the key on, press the "starter button", and give power to the bike. All ignition/engine related devices are connected; blinkers, headlight, the works are not.  However, when it starts, I really have to give it choke and gas back and forth. It REVS loud and then goes to a rough idle for 10 seconds (I have to be doctoring the throttle) and then dies. Ive noticed that exhaust 3 & 4 are HOT but 1&2 are cold. I do have spark although the plugs are old. ironically I was having leaking problems in the 3/4 carbs but those seem to be working?

Anyone have any ideas? Im thinking there is a fuel issue with 1&2 carbs? Maybe a clogged jet from some dirty gas, or something up with the floats? I know that my auxiliary fuel take hose runs down into a T connection on the cards with one hose going to the 1/2 carbs and the other to 3/4. Could this be the connection? Notable caveats below.

-Set points timing and is still good. I have dynatek electric ignition.
-Carbs are original but I rebuilt them a while back (thanks to Classic Octane)
-I haven't really had the engine running long enough to fine tune the carbs with the idle screws, but they are bench synced at about 1/8 inch.
-Modern regulator rectifier
-Modern fuse box
-New starter solenoid
-New battery 13+ volts
-My ignition coils are pretty, uhhh, ugly you could say. they were shot and I was able to do some rewiring so they fire and give spark when I test them grounded on the engine (pretty sure spark isnt the issue.)
-4 pipes run to a cutoff exhaust (plan to customize exhaust when the time is right.
-currently not using air filters on carbs

Also want to check = so my choke is naturally closed when the bike is at rest.  when I see videos of other people using their choke, it seems to stay in position. Mine is almost spring loaded? There is always tension on it so it is (preventing additional air from going into the intake) and I have to hold it up to open it up to allow additional air into the intake.) Is this correct? I feel like this is bassackwards.

Questions are encouraged! I can also take some pictures tomorrow.

Thanks!

[bryanj]

If yours has the choke "knob" by the clocks there is a nut under the rubber cover at the top that increases friction on the solid part of cable to make it stay open, frequently breaks off and only fix is new cable.
Your other problem is carbs aimt clean enough especiallyif they are the PD type

[goodtryer]

Are 1&2 getting fuel? Try the drain screws on those carbs. Are the spark plugs wet?

Also, it's not going to idle nicely without the airbox & filter installed. It'll run but you'll have to fiddle with it and/or set a high idle speed.

And like bryanj said, the carbs aren't clean enough. I have a 77 550 and it took multiple attempts to get the carbs right. Many people don't like the PD42 and it's not unjustified. I've just chosen to work through the issues as those are what came with both my bikes. Once dialed in, I think they're fine.

For the choke, you could temporarily use a spring clip or locking foreceps or vice-grip pliers to GENTLY hold the cable in the choke position.

Good luck!

[Freebirdbeachbum]

It's almost always the carbs. I'd go thru each one thoroughly ensuring all passageways are clear, the floats are floating, and the choke mechanism is working properly. I purchased an ultrasonic cleaner and it's the best investment in tools, other than the lift, I've made. Good luck.

[Don R]

 I had a goldwing that opened the choke by it's self.  I split a short piece of rubber hose to put under the knob. When not in use I slipped it over the clutch cable housing. Temp. but effective.
 Check for plugged exhaust, gel in aftermarket fuel filters, rust or debris in fuel tank or old fuel hose that's bad on the inside.  A few things that bit me in the past.

[dave500]

check the plug caps resistance,if they are the old factory ones theyll probably tired,your looking for say 5000 ohms.

[newday777]

Welcome aboard dramabean

Did you get this resolved? (No updates......)

You mentioned you cleaned or had the carbs cleaned at some point.... What process was used to clean the carbs? Your description sounds like they weren't cleaned good enough and left hardened gas/rust in the fuel ports of the carbs.
What kits were used to rebuild the carbs? This also is a key factor in rebuilding carbs.

Choke cable... Isn't there a knob below the pull to tighten the friction on the cable?