Speaking of sparking

[Guest]

Hey all I have a quick question, I know its not on a GS but I can't imagine that the concepts are very different. Later on today a friend is bringing over his 77 CB550 to work on it. It idles great when hooked onto a running car battery thru jumper cables, but rougher once disconnected. Properly gapped spark plugs and battery are new.

The poor bike has been really roughed around through its life, stolen at some point and now there is a toggle switch under the seat to turn it on, and another toggle switch to engage the starter. I take that as a bad sign and plan to replace at least the ignition switch with a push button, preferably waterproof plastic or something. I'm sure it could use to have its connections replaced or cleaned, but as for this idle problem I'd like to address it rather than just replacing everything and hoping it improves.

Where should I start?

[Big T]

Sounds like bad battery/charging system

The Stator papers work for any bike

[SqDancerLynn1]

stator paper is a good place to start. I would make sure the battery is good before starting the tests

[Speedo]

I second (third) BigT and SqDanceLynn's comments: get educated, get a multitester, read the Stator Papers, perform all tests (also extremely similar tests/versions of this are on several other bike sites - no idea who copied whom, but all good and all very applicable).

Where should you start? Give us more info, we'll give you better advice.
* ONLY idle not good? What about when you rev it?
* Ride it? How does it run when you ride it? Idle is only one of three carb circuits. This would be pretty important to know to get decent advice.
* Car battery has far more "reserve" voltage capacity that bike battery, so one of my guesses is you are not getting good/full voltage to your coils. Do this test:
1. get your voltmeter out. Set to 20volts DC. Put positive on coil positive connection, negative lead to ground (engine or frame bolt should be fine).
2. fire up the bike
3. should read between 11 and 12 volts.
4. if, like many of us with old bikes with old wires, reading is less (mine read 9.4 volts on both coils), consider doing the "coil relay modification". Directions on the GS website. Makes HUGE difference. My readings at the coils went up to 11.9, the bike starts instantly, and runs much much better overall (idle, mid range, and full throttle). Cost is about 10 bucks.

* Do the coil test and/or modification before you suspect and/or get into the carbs.

By the way:
Toggle switch to run starter would have no effect once bike is running.

Toggle switch to "turn it on" replaces kill switch I'm assuming. Could be a problem. Trace the wires, check resistance; at least visually inspect. Find connections and you can run a temporary new wire to either confirm contributing to problem or rule this out.