electrical diagnosis for dummies

[fhauler]

I am not a motorhead but appreciate those who are. I am a experienced BMW rider with about 1,000 Ducati single miles under my belt from Motogiros.

Problem is: I have a newly assembled 250 nc bitsa which ran great for about 35 miles (I did have the light on as required in Virginia) then died at a stoplight. My builder buddy is busy at the races in Laguna Seca so I won't ask him until he gets home. I have taken the battery out and recharged but now can't get a strong sound from the horn or a bright light. Of course it won't start through either a kick or a bump and my leg is getting sore. Has the rectifier gone bad in this short period? I do have another battery on order as a back up.

Any obvious plausible causes of this electrical weakness? I have admitted my limited knowledge so flaming would not be helpful.

Thanks,
Doug

[wcorey]

Welcome to the site.

My first guess as it's a new build would normally be that the (too high wattage) headlight eventually drained the battery and the alternator alone can't keep up, but since you've charged the battery and still apparently have a low voltage condition then the battery itself becomes the prime suspect. Though with the headlight off, the alternator should be able to run things on it's own, which then possibly implicates the alt or reg/rec.

Have you checked the voltage of the battery to see if it's ok? Even if it's fairly new, vibration or a bad reg could possibly have shortened it's life, though if you're running the headlight all the time a bad reg is less likely the culprit.

Next would be to put an ammeter between the battery and positive connector to see if excessive current is being drawn. something could be partially shorted.

What wattage headlight? The alternator will only support so many watts for so long (particularly with a lot of low rpm riding), then it's all up to the battery from there.

That's some basic obvious stuff but there's plenty more to check as possible causes are eliminated.

Bill

[fhauler]

Bill,

Put new battery in, cleaned leads and applied dielectric grease to bolts. Started on second kick and ran well. Noticed a fair amount of sulfate on leads which is strange since they were only installed within the last month. Ran the bike again after supper and it started easily but ran rough? Did not run with lights on either time.

Will try recharged old battery again to see if the leads were the issue. Will check plug as well on rough running issue.

Cheers,
Doug

[DewCatTea-Bob]

" Problem is: I have a newly assembled 250 nc bitsa which ran great for about 35 miles (I did have the light on as required in Virginia) then died at a stoplight. "

____ If your lights were left turned-on for the entire 35-miles, then your charging-system must likely be at least helping the battery with powering your running-loads, (in order to have gotten that far during normal city & outer-city riding, without dieing sooner).


" I have taken the battery out and recharged but now can't get a strong sound from the horn or a bright light. "

____ That would of-course indicate that your battery is no-longer good at taking and/or holding a worthy charge, (so that leads me to believe that your battery [or bat.charger] is defective or too-old/worn-out).


" it won't start through either a kick or a bump "

____ If the battery hasn't become too much of a load itself, then (with a stock charging-system, and with lights turned-off), you should be able to get your engine started-up with a decent 1st.gear push-start . _ If not, then (assuming your alt.rotor is still properly timed), it may be that the diode which rectifies the alt.circuit that's at peak (positive) power-output when the ign.points open, has gone bad. _ That possibility would mean that your charging-system is then providing only HALF power-output, which would not be sufficient to keep a battery from becoming too run-down while running with lights turned-on.
__ If your new-battery seems to also allow the same discharging-situation, then next-time please be sure to tell us whether your rect.reg-unit is a stock-type r.r-unit, (or whatever type you have installed),, and also, please make note of whatever the power-rating is of your Duke's headlight, (such as 25, 30, 35, 45, 55 watts, etc.).


" Has the rectifier gone bad in this short period? "

____ So was your particular r.r-unit a new one ?
__ Anyhow, it's quite doubtful that any rectifier would happen to encounter a reason to go-bad during your 35-mile ride !


Hopeful-Cheers,
-Bob

[fhauler]

First battery charges up very quickly but won't hold charge. It is practically new but must be dead. Can it be killed by electrical system?

Thought about rough running last night and sure enough choke cable had slipped the lever and I had run with choke on. (Thank goodness not for very long.)

This morning bike finally started after x kicks with second battery and ran well. I am not sure about rectifier type and will have to wait for return home of builder/buddy for more info. I know that it is not new and is possibly from a small Honda. Will check bulb watts later in the day.

After dealing with leaking fuel filter, I must have flooded it and worn out kicking foot for this morning.

Not quite ready for prime time but I have a glimpse of what a fun bike it will be.

[DewCatTea-Bob]

" First battery charges up very quickly . "

____ That's what's expected from a battery which has lost the use of the majority of it's plates' surface-area.


" but won't hold charge "

____ That's what's expected from an old used battery which has built-up material (on it's inside-floors) high enough to short-out the plates (in at least one cell).


" It is practically new but must be dead. "

____ Strange ! _ It must be defective in some way.
__ What type of battery is it ?


" Can it be killed by electrical system? "

____ Certainly not by a STOCK Ducati charging-system, especially if you ran with the lights always left turned-on !
It's more likely that a battery-charger with too great of charging-power was once connected-up for too long, (thus likely overheating & warping that battery's plates).



" I am not sure about rectifier type
I know that it is not new and is possibly from a small Honda. "

____ Here then NO-DOUBT is THE source of your charging-issue ! ...
I believe that all Honda systems (and of most-all other Jap.bikes), employ 'full-wave' rectification, and thus such a non-stock r.r-unit will not work connected to a n-c.Ducati alt.stator (that's been circuited to work with a stock-type 'dual half-wave' rectifier).
So I have little-doubt that your buddy (doing the work for you), fully understood what he was actually doing (when he connected-up the non-stock r.r-unit).
__ NOW that you've more properly enlightened us with the very-USEFUL information that your Duke's rectifier is not a stock-unit, then-thus that which I previously wrote before:

(with a stock charging-system, and with lights turned-off), you should be able to get your engine started-up with a decent 1st.gear push-start . _ If not, then (assuming your alt.rotor is still properly timed), it may be that the diode which rectifies the particular alt.circuit that's at peak (positive) power-output when the ign.points open, has gone bad. _ That possibility would mean that your charging-system is then providing only HALF power-output, which would not be sufficient to keep a battery from becoming too run-down while running with lights turned-on.

is no-longer as pertinent, since our prime-suspicion for a more likely malfunction has come-to-light, (as you likely have the wrong type of rectifier).
__ Now we need to learn what your installed r.r-unit actually is (and whether or not any functional-use could possibly still be made of it, on your Duke).
We also now need to know exactly which twin-yellow-lead alternator-model your Duke probably has... So please provide at least the first three digits of your Duke's motor-number.
__ At this point, I of-course can't know how whatever r.r-unit you're employing could possibly have been responsible for the ruining of your first-battery but, since it's now a certainty that your concocted charging-system is faulty, you should not take any further chance of possibly harming your new new-battery.



" I have a glimpse of what a fun bike it will be. "

____ Indeed. ...
So long as you're not in any great hurry to get to someplace (with insufficient time to do so), then most-any 250-Duke can provide a very-PLEASURABLE ride-experience !


Duke-Cheers,
DCT-Bob

[fhauler]

Started and ran well today! Did about 12 miles on two separate occasions.

Engine # number begins with 101. Yausa 38B-6A batteries. Have been using new Genius 6 volt battery charger. Rectifier questions and alternator wires question will have to wait. Off-shore contact believes Honda trail bike rectifier will work with a supplied schematic. First battery seems kaput.

Thanks for your comments.

Cheers,
Doug

[DewCatTea-Bob]

" Started and ran well today! Did about 12 miles on two separate occasions. "

____ The large battery alone (without charging-system help), can handle that distance even with lights (under 45w) left turned-on.
So you should've checked it's voltage-value before & after, (cuz it was probably getting run-down).


" Engine # number begins with 101. "

____ Then your 101xx Duke-motor is a 1966-model, and thus should employ the newer-type 6-pole/4-coil '60w' alternator.


" Off-shore contact believes Honda trail bike rectifier will work with a supplied schematic. "

____ Unless it's a 'half-wave' type rectifier, (doubtful !),, it's not such a simple hook-up connection for N-c.models ! _ UNLESS... did your builder-buddy already complete the common-operation of dis-grounding the stock internal alt.stator-leads (so as to then be able to work with a full-wave rectifier) ?


Hopeful-Cheers,
-Bob