Motoscrubs.com

Okay, I know this is another electrical post, but I am struggling here. On a suggestion from the forum with my no start issues, I proceeded to check my timing and ignition, I was getting consistent spark but the engine wouldn't start. Upon inspection I noticed my points were pretty worn and my condenser's wires were frayed. So I replaced both and adjusted timing. Okay, no big deal, except now I might get a spark on the first kick and then no spark at all. I checked the following:
Points gap
Points showing continuity when closed
HT coil 3.9 ohms

My bike is a bita with what appears to be a 1966 Scrambler engine, 3 wire AC ignition, AA367B AAU, timing at 21 degrees.

Any ideas?

Spark plug wet? Copper wire HT cable? Fires on compression stroke?

Often times a no-spark condition can be a bad condenser. From a direct current (DC) standpoint the condenser is supposed to appear to be an open circuit. Condensers can fail in such a way as to become a closed circuit which shorts the points to ground quite effectively killing all spark. Sometimes a NOS condenser can have "dried out" on the inside.

A 'quick and dirty' test might be to pull the condenser wire off the points and try kick-starting the bike again. If the combustion comes back or if your spark becomes visible at the plug when it was not there before the condenser is almost certainly at fault.

It is my understanding that the condenser's purpose is to arrest the high voltage spikes generated by the primary side of the ignition coil when the points switch it on and off. Without a condenser for any prolonged period, a high voltage arc would jump between the two points plates which will create pits (microscopic maybe and hard to see with the naked eye) in the highly conductive material that is thinly plated onto the points and the points would be ruined at a rather fast rate.

But if you have no other spare and/or known good condenser on the shelf, a quick test with the wire lifted off the points plates should either tell you if the condenser is bad or if you can disregard it as a suspect.


Jim

Just curious, if the timing is off (I re-did it, but don't think that it is), wouldn't the plug still spark when grounded on the case when the points close?

When working on these old bikes it's best to remember that everything is OLD! The coil is 50 years old, the wiring is 50 years old. In other words, it's all junk! Don't screw around with it. Trash it all and put new stuff on.

And yes, all other things being okay (which they are almost certainly not), it should still spark even if the timing's a bit off. However, make sure the points gap is correct.

The wires from your mag (or whatever they want to call it) are almost certainly rotten inside the cases. You should pull the flywheel (after marking it's position relative to TDC on compression) then replace all the wiring leading from the stator (along with any other wiring on the bike).

____ Sorry, I only just-now discovered this new thread.



[quote= STEVENM63 ...
" I know this is another electrical post, but I am struggling here. "

____ Still, your other recent related thread could've continued-onward down this road just as well.



" I proceeded to check my timing and ignition, I was getting consistent spark but the engine wouldn't start. "

____ Have you ever had this engine running before ?



" HT coil 3.9 ohms "

____ Your AC.powered ign.system should be equipped with the 'GREEN-label' ign.coil (which I believe rather has a resistance-level of near just 1-ohm) !
So you must either have the RED-label ign.coil or some-odd other (likely battery-powered type) replacement-unit.



" My bike is a bita with what appears to be a 1966 Scrambler engine, 3 wire AC ignition "

____ Of those three stator wire-leads, which wire-color do you have connected to the ign.system ?
The wire-lead color meant for the stock ign.coil is supposed to be 'yellow' and it's connected power-coil/winding should have a resistance-level between .7 & 1.1 ohms ! _ (The most preferred ign.coil should have a resistance-level which 'matches' the same as that of the ign.power-coil [of the alt/mag.stator], so that the maximum-amount of 'energy-transfer' can be attained !)



" if the timing is off
wouldn't the plug still spark when grounded on the case when the points close? "

____ This is actually a very-good question to've asked*about ! ...
Firstly though,, the ign.spark becomes initiated rather when the points open, (not "close") !
__ Anyhow, assuming that you're meaning to refer-to the particular 'timing' of when the contact-points are intended to create the ign.spark,, then in that case, you're correct to surmise that the ign.spark still ought-to (at-least adequately) fire-off even towards the outer settings of the points-timing adjustment-range.
__ However, if the other important 'timing' of the mag.rotor is-not set properly 'timed', then it's likely that any power-pulse sent from the ign.power-coil will happen to be caught in a weaker/reduced state of power-output at the moment in time when the ign.spark creation-intensity has to rely on it.
So if your mag.rotor-timing is "off", then that could be a possible cause of reduced spark-activity.
(* However if the timing of when the contact-points break the circuit somehow* happens to occur at a time that's too far before or too far after the occurrence of the peak-strength of a power-pulse [produced by the ign.power-coil], then the amount of energy-transfer [to the ign.coil] could indeed possibly be too weak to create spark-voltage.)
(* Which could possibly occur if the mag.rotor-timing and breaker-points timing are too far out-of-sync with each other.)


Hopeful-Cheers,
-Bob

STEVENM63 wrote:

DewCatTea-Bob wrote:____ Sorry, I only just-now discovered this new thread.



[quote= STEVENM63 ...
" I know this is another electrical post, but I am struggling here. "

____ Still, your other recent related thread could've continued-onward down this road just as well.



" I proceeded to check my timing and ignition, I was getting consistent spark but the engine wouldn't start. "

____ Have you ever had this engine running before ?



" My bike is a bita with what appears to be a 1966 Scrambler engine, 3 wire AC ignition "

____ Of those three stator wire-leads, which wire-color do you have connected to the ign.system ?



Hi Bob,
Yes I did have the bike running before, but just briefly (5 minutes running after very difficult starting). Running the bike off of the white wire. Replaced the points and condenser because the condenser wires were really frayed and brittle. Reassembled everything and I literally got 2 sparks with the plug grounded against the case and then nothing. At least I was getting consistent spark before. I even tried reinstalling the old points and condenser with no luck.

Could I not be getting anything from the mag? Is there a way to test it's output. What about the coil?

If I am ever to graduate from the simplicity of my Hondas to this bike, I have to get over this electrical hurdle and get this thing running. LOL.









Just curious, if the timing is off (I re-did it, but don't think that it is), wouldn't the plug still spark when grounded on the case when the points close?

____ The part of your shaded-post that 'Quotes' my partial-post must only contain just my post-wording which had been so-far submitted before the time when you happened to find it,, but by the time your response-post became submitted, I know I had much more post-wording completed by then (than that minimal amount which you've quoted & responded to) !
So apparently you didn't refresh the page just before beginning your reply-post. ...
__ Whenever I haven't yet signed-off on my posts, then I'm still more than likely working on completion,, and-so to make-sure you've accessed my yet to-be finished posting in it's most-recent state of completion, then it should always be 'refreshed' just prior to carrying-on with any (further 'get-the-ball-rolling') premature response-posting.
That your early-timing consequently missed seeing more of my (progressing)- post, had led to you prematurely asking your resulting related questions (which wouldn't-have ended-up being quite the same, otherwise).
(This has to do with why I have my particular COLORED-Note placed at the bottom of all my posts !)




" Yes I did have the bike running before, "

____ I'm left to suppose that if the "bike" was running, then the 'engine' probably had also. _ In which case the mag.rotor-timing couldn't have been set so far off as to prevent adequate ign.firing.



" but just briefly (5 minutes running after very difficult starting). "

____ It then seems that the activity-level of your ign.spark was still even then somewhat declined to a rather low-intensity for some reason.
Was that starting-difficulty episode during kick-starting or (higher eng.revving) push-starting ?



" Running the bike off of the white wire. "

____ Again*, I'm left to suppose that you must really mean that just the ign.coil & points circuit are being powered by the white-wire, (as your Duke's entire electrical-system certainly can't be powered by any of the three wires alone !).
(* I may yet have-to give-up my pet-peeve endeavor of trying to curtail everyone's mindset-fascination with the overuse of the term 'bike'.)
__ Why would you've chosen that wire of all the three ?
If your engine happened to have the older '40-watt' stator, then the white (and yellow) wire-circuit (of the ign.power-coil) would be correct for powering the ign.circuit.
However, if your supposed 1966-Scrambler motor still has the stock-type '28-watt' stator-model, then you've quite mistakenly connected-up the low-output of the minor power-circuit that's meant to merely trickle-charge the battery ! _ And that WEAK power-circuit shouldn't even be expected to adequately power-up the stock green-coil, let-alone an ign.coil with 3.9-ohms ! _ (The 'white' power-circuit for charging the battery has a mere resistance-level of just .1 to .3 ohms !)



" At least I was getting consistent spark before. "

____ You must've inadvertently changed something-else as well. _ Do you think you could've possibly got the two non-red wires mixed-up and replaced the yellow-wire with the white-wire ?



" Could I not be getting anything from the mag? Is there a way to test it's output. What about the coil? "

____ Now that my previous-post has been all finished,, if it's presented info doesn't completely satisfy these related questions, then please ask about any of this stuff again.
____ At this point, the bottom-line conclusion for the main-source of your ignition-issue has got to be futilely trying to power the ign.system with the wimpy battery-charging power-circuit !
That you've ever attained any sign of a spark at all (by using the white-wire [from the tapped lighting-coil]), indicates that the mag.rotor-timing must not be set far-off from optimum !
__ And another certainly contributing factor to help take the blame, is that you must be trying to use an ign.coil that's not-only not properly 'matched' for the intended ign.power-coil (connected to the yellow-wire), but is even far-more way,way,WAY-off from being a resistance-match for the white-wire power-coil/winding !!
__ Right-after the very-first day you found you had your ignition-problem,, you then really should've submitted your issue, so that these related matters could've been addressed before you carried-on distressing yourself as much as you must've while trying-to start your engine with such extreme handicaps !


Hopeful-Cheers,
DCT-Bob

____ It's fairly disappointing that we still haven't yet gotten back any report concerning the main suspects I've submitted (for why the ignition-issue has existed) !
It would be of certain interest to know what type of ign.coil has been attempted to be used, and whether it responds with significantly improved spark-intensity when connected-up with the correct yellow-wire (of the intended ign.power-coil).
Also, it could be productive to measure the resistance-level of the yellow-wire's power-coil to make-sure that it's actual resistance is still that which it's meant to be, (at .9 [+/- .2] ohms). _ Then we may (most likely) dismiss Nick's suspicion that any of the "old" wiring shares any actual blame for the ignition-issue. _ (As of-course it would be out-of-line to go-ahead with all the involved-work of replacing any wiring [that's likely not at fault] before dealing-with the [simpler !] more obvious faults at-hand !)
__ Anyhow,, it would be nice to have some more light shed on this submitted topic, (sometime before anyone who's read this thread, gets a chance to finally bite-the-dust) !


Hopeful-Cheers,
-Bob

Bob, actually your interest in my post is timely. LOL. I'm just heading in from the garage. Give me a bit to compose some things and I will post my successes (and failures).

Well, I did some extensive reading of both my own reference materials and information on this site. Unfortunately, no revelation revealed itself. It did inspire me me to do some more extensive troubleshooting which lead me to find a defective condenser (contact fitted over the insulation). I did some more testing reassembled everything. Here is some info

Alt wiring resistance measurements
White = 1.0 (currently connected to ignition)
Red = 0.4
Green = 0.1-0.3

Timing - 21* static
Plug gap - .026

Well the motor now starts, with no kickback like before. It idles nicely, but unfortunately, once you bring it off idle it won't rev. It coughs and stalls with no power.
Here is a quick video. https://www.youtube.com/watch?v=7Y3F-WJ ... e=youtu.be . Notice that when I increase the throttle the engine won't rev up. Also you hear lots of air being sucked through the carb.


So this will be this weeks project. Any ideas