No spark while cranking starter, but sparks when button released?

[gsdelta]

im in the middle of diagnosing my 450 twin. Im getting no spark while I depress the starter button and crank the engine but as soon as I release the starter button I get sparks until the engine stops turning from its own momentum. Sometimes it fires a couple of times as soon as i let off the starter button but not before. Jumping the bike from my car battery makes it run but it stops as soon as i disconnect the jumper cables. Id appreciate any thoughts that might help figure this one out. I have checked and tested the plugs, coils, igniter, switches, continuity etc.

Any help appreciated!

[tom203]

Remember-DON"T jump from a running car-potential for too high voltage.
Do you now how to trigger the starter solenoid right at solenoid, so you don't need to use starter button? (there's a small wire that triggers it). Make sure you're in neutral and on centerstand for safety.

[Redman]

Classic sign of weak battery.
Either because battery is old and weak, or because charging system not functioning well.

What is happening is that when are cranking the starter that is demanding a lot of current from the battery, and the batterys voltage is dropping when trying to produce all that current. On a weak battery the voltage will drop even more than if it were a good battery.
A well charged stronger battery would be able to supply that current without dropping voltage too much.
AN older weak battery will drop the voltage a lot when putting out that much current, may seem okay other wize, but cant put out the high current the staarter will require and still maintain the voltage.

ANd the if the battery is weak enough, the battery voltage drops to below what the ignition needs to work. WHen you let off the starter button, the starter current is no longer there, the battery voltage can go back up, but yet the engine is still spinning for a bit to trigger the ignitor, and you may get a few sparks.

I have noticed that this is the first sign of a battery starting to go weak. THe the engine doesnt start right away, but does start right when let off the starter button. Well, maybe that is the 2nd clue, first clue would be how much the headlight dims when cranking the starter but that is hard to notice since it will dim some even on a good battery.

Try putting a charger on the battery, and see if that improves things for a while. But I suspect you have a weak battery and/or weak charging system.

Also, this situation could be made worse by having bad power connections at the ignition coils where the voltage to the coils is mad even less by the bad connections. The whole situation of no-spark-while-cranking-but-get-a-few-when-let-off-starter is all related to to low a voltage at the igfnition system to operate the ignition system.

Tell us more what you find.

Welcome to GSR (and add your location to profile in UserCP, and bike to signature line)

Dave



>> later Note:
Oh, now I see your comment about it running when jumped from a car.
Oh, well, then,... it is obvious the problem is related to the battery and/or the charging system.
And maybe you do not have a battery charger.
And maybe you do not have a voltmeter.

You either have a bad battery or failed charging system ... or both now.

And maybe you do not have a volt meter either (you did not mention any voltage readings).

I suppose you could just try a new battery. That will probably get you going.
But also need to check the charging system or you will back dead on side of road on 2nd or 3rd or 4th trip.

You need a volt meter.

.

[gsdelta]

thanks for the advice. I do have a voltmeter that read 12.5 directly across the terminals of the battery but I have not had a chance to read the voltage at various rpms yet. I noticed that the liquid in the battery was about half an inch below the minimum level too. will top up with distiller water and then give the whole thing a good charge. might as well start there with the easy stuff first!

[bonanzadave]

Classic sign of weak battery.

Ill go with that. I had the same issue. Weird thing was it would crank all day. I started looking hard at the coil relay mod and how the possible bad battery affected the latching voltage for the coil. I played around with the connections, including the relay ground, and it started working. Now I have a new battery and the issue has not resurfaced.

[posplayr]

thanks for the advice. I do have a voltmeter that read 12.5 directly across the terminals of the battery but I have not had a chance to read the voltage at various rpms yet. I noticed that the liquid in the battery was about half an inch below the minimum level too. will top up with distiller water and then give the whole thing a good charge. might as well start there with the easy stuff first!

Try a Quick Test,
check results from step #1 and Step #2 : if with key on the voltage drops below 12.2ish volts you probably have a battery issue.
If you get it to run with an external jumper battery go ahead and do the rest of the tests to check charging as they assume the battery is good (which is valid with the jumper battery).

[Steve]

Remember-DON"T jump from a running car-potential for too high voltage. ...

Close, but not quite accurate.

True, the voltage of the running car is probably just above the bike's regulator's set point, but it's the CURRENT that the car is producing that will kill your regulator. It simply can't handle that much current while trying to regulate the voltage.

thanks for the advice. I do have a voltmeter that read 12.5 directly across the terminals of the battery but I have not had a chance to read the voltage at various rpms yet.

The engine speed where I would like to see the voltage is cranking speed. What is the voltage while you are cranking it over?

.

[koolaid_kid]

Close, but not quite accurate.

True, the voltage of the running car is probably just above the bike's regulator's set point, but it's the CURRENT that the car is producing that will kill your regulator. It simply can't handle that much current while trying to regulate the voltage.

I was hoping you would chime in on that particular statement. An automotive alternator is quite similar to ours AFA voltage. The R/R is actually built into the alternator itself, BTW.
(Please don't get mad at me Steve, I realize I used 3 acronyms. )

[Killer2600]

Close, but not quite accurate.

True, the voltage of the running car is probably just above the bike's regulator's set point, but it's the CURRENT that the car is producing that will kill your regulator. It simply can't handle that much current while trying to regulate the voltage.

True but what difference does it make, there is no current off, voltage on switch. The advice of don't hook your bike to a running car because of the voltage it puts out, is still good. If the car put out 10,000 amps at a mere 12.8 volts nothing would happen to your regulator.

I was hoping you would chime in on that particular statement. An automotive alternator is quite similar to ours AFA voltage. The R/R is actually built into the alternator itself, BTW.
(Please don't get mad at me Steve, I realize I used 3 acronyms. )

Charging systems in automobiles have advanced past your technology level, in many new cars the regulator is NOT in the alternator anymore but has been moved to being a function of the PCM/Computer and the computer tells the alternator when and when not to create output as well as how much output to create.

[BassCliff]

Greetings and Salutations!!

Hi Mr. gsdelta,

Even with a good, fully charged battery it is still possible for the coils to be underpowered due to resistance in the old wiring harness. Clean connections are very important. What is the voltage at the coils when you hit the start button? Some voltage drop is normal but if it's 10v or less you may want to take a look at the coil relay mod, if cleaning the wiring harness doesn't improve things. You'll find more on the coil relay mod and much more in the links below.

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[Redman]

thanks for the advice. I do have a voltmeter that read 12.5 directly across the terminals of the battery but I have not had a chance to read the voltage at various rpms yet. .....
....

Good that you have meter, and can use it.

Taking the battery voltage reading with engine running is good for checking the charging system, and, yes, you should do that - - when you get it running.

But relative to your concern for "why not spark when cranking but do get a few sparks when let off starter":
You will want to see to what level the battery voltage drops when cranking the starter. This is more a test of the condition of the battery. Apparently your battery drops the voltage to low enough that it can not operate the ignition system. (I can not tell you what that voltage would be where ignition doesnt work.) And this is happening either because battery is old and weak or because charging system is not charging the battery well, or both the battery is weak and charging system not charging well.

You did say it would start and run when jumped to car. Three things:
1) charging system of car can overpower your chrging system. And car battery can over power your wiring if your battery low. Can reduce but not eliminate this if just connect car battery but not run the car.
2) you say if jump to car batery that can start and run bike, but dies if disconnected. That sounds like both weak battery and charging sytem not charging.
3) You are not going to be able to check your charging sytem voltage reading if cant get it to run. So maybe start with a new battery, then can check charging system.

And let me repeat: If get a new battery and that gets it running, do not think that everthing is okay. DO check the charging system (the quick check), or you may find that bike could die on you again after a few rides.

Dave

[tom203]

I was hoping you would chime in on that particular statement. An automotive alternator is quite similar to ours AFA voltage. The R/R is actually built into the alternator itself, BTW.
(Please don't get mad at me Steve, I realize I used 3 acronyms. )

I've seen alternators that are regulated by the engine computer- the diodes are still in alternator, but the computer regulates field strength to control output.