Bike doesn't start in cold weather

Again use the KISS principle Keep It Simple Stupid , if bike seems sluggish after it heats up points more to CARBS , more than anything . As to your coils 81 to 83 CB 750 Honda coils will swap in and have replaceable wires , can be bought NEW from Cycle Recycle Part 2 40$ each. Inspect your coils are there any cracks in housing ? If you do try these could desolder lead off of old Coils and crimp me connector leads on . As I stated your charging system is WORKING leave it alone , if it was not after about a hour your bike would shut down , your electrical system would only be running on battery power when it drops below 11 volts TCI will shut down. Once I had a mint 82 CB750 custom with 4500 miles, was riding it home from dealer I bought it from , 2 miles from home bike died. Had to pull battery and charge it for 10 minutes and made it another mile , recharged made it home . The charging system was OUT common on Hondas of the vintage as I found out. Replaced vantage regulator still no joy, was ready to try stator, owner of Cycle Recycle Part 2 said it was the rotor , he was right , charged at 13.5 volts , before read 12vlts which was simply the battery voltage. My point of what happened with my Honda the charging system was INOP . Yours is working from what you describe.

 

Update. I just did a diode check on the ignition coils and I'm getting zero. I pl

Okay, if it's working it's working. What I don't understand though is that if the battery reads 12.8 volts before a ride and then I get back and it reads 12.2volts it seems to me that that is not a working charging system. It seems to me that a correct charging system should always keep the battery fully charged but I am still learning about these early 80's bikes and maybe that was the norm. I don't know anymore.
As far as the coils I just did a diode check and I literally got a 0.00ohm reading. I set the meter to ohms 20k and put the two leads into both primary sides. The reading starts at OL and then when I apply the leads it literally says 0.00. I then tried to do the secondary lead reading and got the same thing. I wanted to make sure the meter worked correctly so I tried the diode check on a spare regulator/rectifier I had sitting around and it works fine. I've had no spark situations in the past with this bike so I'm guessing these coils are duds. By the way, I have never ridden more than an hour on this bike so there's that. I'd like to though.

 

By the way, I noticed that the right coil has this extra wire attached to it but the right one does not? (see pics) I couldn't find any dangling wires. Is this just another ground wire of some sort?

 

diode check? ignition coils are ohms tested

 

that's what I meant. I put the meter to 20k ohms and got 0.00ohms. Sorry

 

Here is the other picture of the other coil with the added wire that the right does not have. Sorry for not including this earlier.

 

That appears to be a main harness ground wire (black) and typically they are attached at the coil mounting bracket, but it has nothing to do with the coil(s) itself. The black wire comes out of the main harness and simply serves as a common ground for a variety of circuits on the bike.

You need an ANALOG (moving needle) volt/ohmmeter to work on these bikes. Some of the ohm measurements are way too small to measure with a digital meter (didn't we discuss this before?) . The ignition coil primary resistance, secondary resistance (without the plug caps on the end of the wires), and the resistance of each plug cap would be measured and compared against specs (P.S. specs are specified as being valid at about 70-F). And while you're at it, you should also check the resistance of the pick-up coils.

However, most of the issues that you describe probably have nothing to do with the ignition coils (there can be rare instance when the coils are breaking down as they heat up, but again.....that is rare). You either have fuel system or charging system issues, or a combo of both.

Checking alternator stators: the resistance across each pair (white1 to white2, white1 to white3, and white2 to white3) of the three white wires (white1, white2, and white3) at the connector should be as follows. These tests should be taken while the components are at a temperature of about 70-F:

0.50 ohms +/- 10% for all XJ550 models.


Checking alternator rotors: the resistance across the two lead wires (usually brown and green) at the connector should be as follows. Note that worn or damaged alternator brushes can affect these readings, as can "dirty" copper commutator rings on the rotor face (where the brushes contact the rotor):

4.5 ohms +/- 10% for all XJ550 models.



Checking pick-up coils:
650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range for all XJ550 models.


Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range for all XJ550 models.

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range for all XJ550 models.


Spark plug caps:
10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range for all XJ550 models.

Stock spark plugs:
0 ohms per plug for all XJ550 models.




There are two main types of alternator systems commonly used on motorcycles. Both types depend on a magnetic field, created by magnets in the alternator rotor, to induce an electrical voltage and current flow in a stationary coil of wires-----the alternator stator. If you ever get confused as to which is which, just remember that the rotating component is the "rotating rotor", and the spaghetti-like bundle of wires is the fixed-in-place, "stationary stator"......

The first type is the permanent-magnet rotor system (used on Virago, V-max, and FJR models, among others). In these systems, the fixed-strength magnets in the spinning rotor generate a constant-strength magnetic field, and thus excite the stator coil constantly; thus the alternator puts out 100% current at all times and the voltage regulator merely serves to shunt any excess generated current to ground. The advantage of the permanent-magnet system is a reduced amount of system complexity, but at the cost of increased heat and power losses (since the alternator system is generating power, and thus using up engine horsepower, constantly).

The XJ-series of bikes follows the more common automotive model, which employs variable-strength electro-magnets in the rotor. In these systems, the variable-strength magnets in the spinning rotor, when energized, are used to form the magnetic field which excite the stator. The voltage regulator controls the voltage output by varying the input voltage applied to the rotor's electro-magnets, and thus varies the strength of the magnetic field. If the system voltage drops, the voltage regulator increases the voltage fed into the rotor electro-magnets, thus increasing the strength of the magnetic field that the magnets produce, and therefore increasing the excitation (output) from the stator....and thus the alternator output voltage increases.

In both systems, the stator windings are 3-phase. Each stator wiring bundle (there are 3 of them, and each bundle is called a "leg") kicks out similar voltage, but 120-degrees out of phase with the adjacent leg(s). The resulting AC currents are then rectified (changed) to DC current via a 3-phase bridge rectifier, made up of 6 diodes, such that current in any leg flowing in either direction is directed back into the system as 12-volts DC (actually, around 13.5 to 14.5 volts DC, when everything is working properly).

If you lose a leg, or even a single diode, it is possible to still achieve voltage if the load is minimal, but as current requirements increase, the alternator will not be able to meet the challenge and the battery will have to take up the slack. Of course, as the battery drains, the available voltage is reduced, so the maximum rotor field voltage is reduced, so the current output is reduced, so the battery has to take up more slack, so ....

The end result is the battery discharges and the bike won't start.



There are a number of different tests that can be performed on the regulator and rectifier unit, and it is beyond the scope of this catalog to explain in detail what those tests are, and when and how to perform them. The regulator, in particular, stands "in-between" two of the main electrical components in the entire system----the battery and the alternator----and thus performance of those components must be evaluated before a faulty regulator is suspected. We strongly suggest the purchase of a factory or aftermarket service manual for your bike to be able to properly diagnose and perform electrical system problem solving and repairs!

 

Chacal, it turns out I was using my multimeter incorrectly. I was so excited I went and did a quick test just on the primary connections on the coils. Here are the results:
Left coil - 2.1o ohms
Right coil - 1.9 -2.10 ohms (this one bounced around a bit)

I didn't do the secondary side yet but I believe both of these results are below spec. Like I mentioned before my bike starts MOST of the time but the three times it didn't start this last week have been when the weather was rather chilly around 40 to 45 degrees. It never get's super cold here in LA but my problems seem to be in line with what the catalog on this forum says:

"Although reduced voltage input (and thus less coil output voltage) may not significantly affect engine performance once the engine is warmed up, it can and will result in "hard start" situations when the engine is cold and/or when the choke system is engaged (since richer fuel mixtures require a much stronger spark to create ignition of the fuel mixture)."

What do you think?

 

you should start by checking out your charging system. ohm it out. remove the cover for alternator to check the commuter rings for being clean and brush leangth to be in spec. clean all the connectors in the charging system . at the regulator at the battery make sure the grounds are clean and secure.

your charging system numbers are a little out of spec.
it could just be a bad battery no matter how new your battery is. the 14 volts should always be there at 2000 rpm.

 

I 100% agree. I just measured the stator and it read .2, .3, and .5ohms. It's the stator. It's always been. I just get too hung up about buying something else for this frickin' bike because I already invested way too much. What can you do. Also, the ignition coils read 2.1ohms on the primary side and I couldn't even get a reading on the secondary side. With or without the caps. Screw it. I'm buying new coils and a new stator.

 

I would continue to look at the entire charging system

 

before I buy a new stator could anybody tell me what the ac output should be at the three white wires coming directly out of the stator both at idle and at 3000rpms? I can't seem to find that anywhere. thanks

 

there is no spec in the manual for that.

 

Per Chacal, I bought an analog voltmeter but I got mixed results. It read 0.2 ohms across all 3 sides of the stator which is what my digital multimeter said. However, it also said 0.5 ohms on the primary side of my ignition coils but when I checked again with my digital multimeter it read 2.2ohms. Yes I cleared the analog to zero every time I used it and it still gave me this weird result. Anyway, I checked the coils again on the secondary side but this time I pulled the caps off and they all read above 8000ohms which is in spec so I can conclude that my ignition coils are fine. However, it's my plug caps that were funky. I could barely get a reading on two of them and the other two I couldn't get a reading on them whatsoever. Going to get some new caps.
It will be interesting to get a new stator on this bike. My charging system has been a headache for over a year now.

 

Quick question, I stumbled upon a used stator that reads 0.8 ohms on all three wires. Is that number unusually high? Is that a good stator?

 

specifications should be:

0.50 ohms +/- 10% for all XJ550 models.

 

I understand that but im curious if it consistently reads higher on all three wires is it still good? What does a high ohm reading on a stator mean?

 

it could be your meter, touch the probes together and see if you get a reading. could be you have loose plug ends that go into meter.

another problem with reading a coil of wire is the inductance caused by all that wire.

a good test for your meter would be get a few 1% resistors .5 ohms and read them see what you get.

.8 may be good as they all read the same but is a lot of work to find out.

 

So, I believe my hard starting issue was the fact that there wasn't any gas getting to the cylinders. What solved it was simply putting the petcock on PRI and usually after about 30 seconds the bike starts right up. I'm curious why the bowls aren't staying filled up?
I'm also getting some popping on deacceleration which I understand means I'm getting a lean mixture. I turned all the pilot screws another half a turn out which means all four of them are 3 full turns out now. As a result the bike idled higher which was solved by turning the idle screw down of course but I'm still getting the popping. Should I just keep turning the pilot screws out until the popping stops? Is it that simple?
Finally, I'm getting a slight hesitation when I open the throttle in first gear which causes the bike to sputter for about a second but then it catches on and runs good. I soaked the carbs in Berrymans to see if anything might be gummed up. Also, when I cleaned the carbs about 6 months ago the PO had 115 size jets and I put the stock size, 112.5, back on. I'm curious if I should go back to the 115's.

 

Did you have the entire rack disassembled with all rubber bits removed before you soaked them?