A disconnected battery will lose about 1% of it's capacity per day. Slightly more if it is connected to the bike's rectifier.
The battery is a chemical converter. The chemical action slows with lower temperature. While this can help the battery last longer, it also lowers it's peak output delivery potential. You can expect lower voltages from the battery when cold.
This is significant because the coils produce a spark voltage proportional to the battery voltage. If the voltage is low enough, no spark occurs. Remember this, as there are many other factors that can produce low voltage at the coils besides low temps.
1. The electric starter draws heaps of power and lowers the battery voltage in the process.
2. A cold motor has thicker oil, particularly if you are using a 20-50W, and the engine has more resistance to turning the crankshaft when cold. This makes the electric stater draw even harder from the battery, lowering the voltage.
3. The headlight draws power from the battery lowering the voltage. The electric start button should turn off the headlight while the electric starter is engaged, but if you have a headlight/lighting switch turn it off for starting.
4. Old spark plugs require more voltage to spark then new ones. This is a threshold thing. The coils develop voltage only until the two plugs fire at once. However, this assumes there is enough primary power on the coils to reach this firing threshold at the coils output.
5. It is possible that the spark plug cap resistors have failed. These can open creating an additional gap that must be bridged in addition to the spark plug gaps in the cylinders. More gap means higher required voltage potential. CB550's usually have 10K resistors in the plug caps.
6. Resistor plugs seem more commonly available than the correct non-resistor plugs. If there is an R in the plug number, there is an additional resistance to overcome before achieving spark at the plug gap that must be developed at the coils and derived from the battery voltage.
7. There are several connectors and switches in series between the battery supply terminal and the coils. If any of these connection adds Resistance from oxides between the contacts, voltage is lost at each one. If there are ten connections and each one loses .2 volts, the voltage the coils operate with is 2 volts less than intended.
8. Soot and excess fuel on the spark plug center electrode insulator can shunt the voltage at the electrode to the spark plug body (ground) without jumping the gap at all. No spark no fire.
9. Measure the voltage across the point gap ignition on, with and without the headlight. See why I said to turn the headlight off? Anything below about 9V is trouble. If the bike won't start, take a look at points voltage with the electric starter engaged.
10. Many of the above, if present, can combine and compound the low voltage presence at the coils.
Enough about electrical causes. What about fuel?
I have noticed all my 550s are cantankerous and more subborn to start the longer they have sat without running. Fuel flow has a cleaning effect in the carbs and all the little orifices and passageways get cleaned with this flow. The carb bowls are vented to the atmosphere. So, as the fuel evaporates it leaves residue and gummy deposits that upset smooth flow of fuel through the carbs. The deposits plug things up eventually and the smallest orifice, the slow jet, usual suffers the most. It doesn't take much gum to reduce an orifice size of .016 inch which is the slow jet. However, the emulsion tubes for both the slow jet and the throttle valve also have holes about this size which flow air to premix with the fuel before entering the main carb throat. When these holes change in size, the bike just doesn't run right, and starting the bike can be more problematic.
"When I rolled it off the truck, there was fuel coming out of I think the overflow lines from the float bowls."
This is not a good sign. I would drain, catch, and examine the contents from each carb bowl. Each has a drain screw. Chunks larger than .016 inch are bad news for the slow jets and even smaller chunks can block the float valves from closing, raising bowl fuel levels so they overflow out those tubes. If the bits are rust colored, you probably have a fuel tank issue to address.
My starting procedure. Continue on this plan until bike starts.
1- Headlight off.
2- Full choke (lever up on the early Cb550s)
3- Throttle (about 1/4, so the carbs can source fuel from the throttle valve, too.)
4- Electric start attempt for about 15 seconds. If the bike hasn't run for more than 5 days and hasn't caught yet, I switch to kick startin order to save the battery and keep ignition voltage high.
5- 5-10 Kicks.
6- Throttle now goes to max
7- 5-10 kicks
8- Choke off, throttle still at max
9- 5-10 Kicks
10- Throttle at 1/8
11- 5-10 kicks
12- If the motor is trying but not staying lit, start over at #2 (skip #4 if battery is clearly weak).
13- If no encouragement from the motor attempting to run, it's spark check time, pull a plug sniff for gas, lay a plug on a cylinder and watch for spark. If spark present and plug drenched in gas, its flooded. Either wait awhile, or pull all plugs for inspection and kick lever the bike a few times to clear the fuel from the cylinders. Reinstall plugs and remove air filter. Begin again at #1.
If at any point the neutral lamp gets dim, suspend staring until the battery is recharged.
Sorry this got so long...
Cheers,
