Spark quality and coil questions

[narrow_monza]

" I have kicked it a few times with the the ignition circuit directly connected to the ignition power coil
and saw a blue spark that seemed healthy. "

____ Okay, GOOD ! ... Then that means we know that everything involved is already quite well enough with the regular operation of your ign.circuit. _ And if that's indeed the way you now have everything currently set-up, then-next we're ready to continue-onward & check that your present mag.rotor's phase-setting is as intended to work with your bridge-block's rectified output.
__ So, (assuming that your ign.circuit is still set up & working), next you need to retest for ign.spark with the bridge-block inserted in it's place within the entire ign.circuit. _ Because if you then no-longer get ign.spark (once the intended rectifier has been inserted into the circuit), then we know that your mag.rotor's present phase-setting happens to not be phased to work along-with the intended negative-ground battery-system.
__ There's two simple methods to deal with such a 50/50 happen-chance circumstance ! ... The most difficult method is to re-phase the mag.rotor on the crankshaft.
This is why I've asked about the present installation status of your mag.rotor.
So can you please confirm how such things are now currently standing, in this regard ?

I will wire up the bridge-block and check for a spark. I'm assuming I don't need to have the battery in the circuit for the purpose of this test, just the 2 diodes from the AC inputs to the negative output, right?

[DewCatTea-Bob]

____ Sorry I didn't notice your new post sooner, as it must've gotten posted on this new page whilst I was still editing my previous post on page-2 (before I finally 'signed-off' on that post) !



[quote= narrow_monza ...
" I will wire up the bridge-block and check for a spark.
I'm assuming I don't need to have the battery in the circuit for the purpose of this test, "

____ You've assumed correctly, so forget the battery for now,, as the battery will be part of another/UNinvolved circuit (which has nothing to do with your ign.system) !



" just the 2 diodes from the AC inputs to the negative output, right? "

____ The AC.power wire-lead from the ign.power-coil should terminate to one or both AC.inputs of the bridge-block,, and-then (preferably*) the b.block's negative-output, (* not it's '+' output), connects to the ign.system (at the same connection-point as where the AC.power-lead did).
__ Whether you still get ign.spark or not,, you ought-to also try-out connecting just the b.block's POS.output to the ign.system as well, so as to confirm that only one output or the other will allow the ign.system to create a spark, (thus confirming that the b.block's diodes are functioning as expected).
There's at-least a 50%-chance that the 'neg.output' will still allow spark to be created,, but if IT doesn't, then you'd either have-to consider a positive-ground battery-circuit, OR-else rotate the mag.rotor a quarter-turn (in relation to the crankshaft [AND-thus also in relationship to the points-cam orientation as well] ).
__ Please let us know how these tests turn-out for you.

____ I often wait to-be inspired by posted-questions, leading to becoming motivated enough to post extra tech.details,, but I've already waited too long to get the following related-stuff posted.
__ Here's some tech.detailing as to what's going-on with the diode-steering of the NEG & POS component-halves of the AC.power...
The ign.power-coil of Ducati's four-pole alternator creates 2 complete AC.cycles per revolution,, so-thus every time an ign.spark is created, there's been 4 complete AC.cycles consisting of 4 positive & 4 negative power-pulses ! _ And normally (as stock), ALL of those power-pulses are left allowed to be dumped towards the powering of the (non-battery type) ign.system, even-though the ign.system only requires merely a portion of JUST one power-pulse (per 4-stroke/Otto-cycle) !!
So considering the dwell-ratio of the points-cam,, that means that two of the un-required power-pulses are wasted through the ign.coil circuit to ground, and the remaining five p.pulses are rather more directly wasted to ground (by 'SHORT-circuit' through the contact-points) !!
__ Of-course it would be most desirable to save & utilize all seven of the excess power-pulses (per Otto-cycle), but the diodes can only separate the positive-pulses from the negative-pulses,, so-thus three of the NEG*pulses still have-to be allowed to go to waste. _ However all four of the POS*pulses can be saved & diverted to power something-else (such-as battery-charging) !
(** NOTE that if the N. & S. magnetic phase relationship of the mag.rotor is located (on the crankshaft) 90-degrees off, then the POS & NEG roles are thusly reversed.)


Enlightening-Cheers,
DCT-Bob

[narrow_monza]

" just the 2 diodes from the AC inputs to the negative output, right? "

____ The wire-lead from the ign.power-coil should terminate to one or both AC.inputs of the bridge-block,, and-then (preferably) the b.block's negative-output, (not the '+' output), connects to the ign.system (at the same connection-point as where the AC.power-lead DID).
__ Whether you still get ign.spark or not,, you ought-to also try-out connecting just the b.block's POS.output to the ign.system as well, so as to confirm that only one output or the other will allow the ign.system to create a spark, (thus confirming that the b.block's diodes are functioning as expected).
There's at-least a 50%-chance that the 'neg.output' will still allow spark to be created,, but if IT doesn't, then you'd either have-to consider a positive-ground battery-circuit, OR-else rotate the mag.rotor a quarter-turn (in relation to the crankshaft [and-thus the points-cam orientation] ).
__ Please let us know how these tests turn-out for you.


Hopeful-Cheers,
-Bob

Thanks Bob, I will run the tests this weekend and post the results.

[DewCatTea-Bob]

[quote= narrow_monza ...
" I will run the tests this weekend and post the results. "

____ Until then, how-about telling us about* the bridge-block you found ?
(* Such as it's price/cost & particular specs, and where you got it from.)


Hopeful-Cheers,
-Bob

[narrow_monza]

[quote= narrow_monza ...
" I will run the tests this weekend and post the results. "
____ Until then, how-about telling us about* the bridge-block you found ?
(* Such as it's price/cost & particular specs, and where you got it from.)

Hi Bob,
I got the following two bridge blocks:

NTE5322 Silicon Bridge Rectifier 200V 25A (Fry's Electronics $5.19)
NTE53016 Silicon Bridge Rectifier 200V 50A (Radio Shack $3.72)

I think I can use either one.

_adrian

[DewCatTea-Bob]

[quote= narrow_monza ...
" I got the following two bridge blocks:
NTE5322 Silicon Bridge Rectifier 200V 25A (Fry's Electronics $5.19) "

____ I believe that rating is the most common, and-thus is usually the best-deal,, although the price you've listed is about twice what it usually sells for, (at-least before the last few years !).


" NTE53016 Silicon Bridge Rectifier 200V 50A (Radio Shack $3.72) "

____ Now that's a much better deal !
In the past, R.S. didn't carry a b.block with that particular high-rating. _ And connected-up in the (irregular) manor I've suggested, it would then be capable of handling up to 100-amperes (which is over a dozen times greater than is needed for the intended circuit) !



" I think I can use either one. "

____ Certainly indeed-so ! _ As either of those is way-over rated for the intended job !
And both ought-to be easy to mount (with a single bolt). _ Have you yet chosen a particular mounting-location (for one of them) ?


Hopeful-Cheers,
-Bob

[narrow_monza]

[quote= narrow_monza ...
" I got the following two bridge blocks:
NTE5322 Silicon Bridge Rectifier 200V 25A (Fry's Electronics $5.19) "

____ I believe that rating is the most common, and-thus is usually the best-deal,, although the price you've listed is about twice what it usually sells for, (at-least before the last few years !).


" NTE53016 Silicon Bridge Rectifier 200V 50A (Radio Shack $3.72) "

____ Now that's a much better deal !
In the past, R.S. didn't carry a b.block with that particular high-rating. _ And connected-up in the (irregular) manor I've suggested, it would then be capable of handling up to 100-amperes (which is over a dozen times greater than is needed for the intended circuit) !



" I think I can use either one. "

____ Certainly indeed-so ! _ As either of those is way-over rated for the intended job !
And both ought-to be easy to mount (with a single bolt). _ Have you yet chosen a particular mounting-location (for one of them) ?

I haven't decided where to mount it. I guess it depends on how hot these blocks run. I was thinking either bolted to the frame under the gas tank (near the coil) or inside the headlight shell? Any suggestions?

Oh and I need to check for a spark first.

[DewCatTea-Bob]

[quote= narrow_monza ...
" I haven't decided where to mount it. "

____ While we've discovered that your motor is a Motocross-type, I don't recall whether your frame is same or Monza-type. _ If Monza, then it should include a pair of flat brackets (originally intended for the stock regulator-unit), located under the front-end of the seat. _ If actually there, then mounting the b.block on one of those flat-bars would probably be best. _ Otherwise, whether you chose the battery-bracket or elsewhere, is often dependent on the remaining length of the alt.stator-cable & it's contained wire-leads.



" I guess it depends on how hot these blocks run. "

____ Normally, diodes get fairly hot only-when conducting current-juice near their rated amp.value. _ So-then assuming that a diode-bridge's ampere/current-handling 'rating' is to-be taken advantage-of by over 50%, then it's expected to-be 'heat-sunk' to something which can absorb & disburse the block's heat.
However since you've got a b.block which will only have-to handle no more than just 5 or 20% of it's rating,, then it shouldn't ever feel very-warm, even when not heat-sunk.



" I was thinking either bolted to the frame under the gas tank (near the coil) or inside the headlight shell? "

____ Either location could be done,, it's up-to you, as you'll have-to arrange the involved wiring (within whatever chosen area).


Hopeful-Cheers,
-Bob

[narrow_monza]

Hi Bob,

On a side note, would I be causing damage to the engine if, for the purpose of checking for a spark, I use the kickstart while the sump is completely drained of oil? I have sprayed some fogging oil in the spark plug hole in the hope that it will protect the cylinder walls. I haven't put any oil yet because I still have the clutch cover off.

Thanks

-adrian

[DewCatTea-Bob]

[quote= narrow_monza ...
" would I be causing damage to the engine if, for the purpose of checking for a spark, I use the kickstart while the sump is completely drained of oil?
I still have the clutch cover off. "

____ While that's indeed a concern, (which of-course is certainly not-good for the engine),, any frictional-wear shouldn't amount to anything notable, (for the less than a dozen engine turn-overs which you may take just to confirm ign.spark).
__ However the kick-lever can't be used without the left-side/primary case-cover held in place, anyway ! _ (So instead, you could try rotating the rear-wheel while shifted into gear.)



" I haven't put any oil yet because I still have the clutch cover off. "

____ About a quart of oil (in an otherwise empty*sump) can still feed the oil-pump, without leaking over & out of the left-side of the opened motor-case.
So if you expect to turn-over the engine more extensively,, then it would be good to have such a minimal amount of oil within, so as to allow the oil-pump & passageways to sooner become primed-up.
(* Hopefully, you already have the oil-sump pretty-well emptied-out.
And certainly before pouring-in your motor-oil, it's always good to first shine a light through the drain-plug opening and check that all's-well for the filter-tube to-be properly*fitted into place. - [* If not "properly fitted", then the 'tube' may become warped.] )


Hopeful-Cheers,
DCT-Bob