Topic: Ignition system questions...

[Fabricator]

Howdy all,


   First off, I searched archives before posting this, so if there is a previous article that answers these specific questions; shame on me.

Background of my question comes from a fellow forum member's bike (Trav-i).  I was assisting him (well, trying to) with some ignition/electrical troubleshooting.   It was running rough (The proverbial "IT" was his '73 model 750 with stock ignition), and later turned into a case of "no spark" at all.  During the "pokin-round" with a meter, I decided to verify that the condensers were doing their job..... Which leads me to my question:

Testing condensers: Clymer manual says 5K ohms from case to lead.  An electrically minded friend indicated that I should only use an analog meter for this, and not my nice Amtek digital.  I could not get a reading on the "suspect" coils on Travis' bike, as the reading would simply climb from 14-15K to oblivion.   To make sure I was not going crazy, I performed the same test, on the condensers' of the two running bikes nearby...Same result.  Is Clymer wrong?    I also used his "Blue-Point" meter, and a cheapie Sears meter as well, as I wanted to eliminate "meter failure" from the picture.  The next thing I did was connect some test leads to the condenser (Case and lead) and attempt to charge the condenser with a new, and properly charged 12v battery.  I could not get them to discharge and produce a spark... I then did the same thing with the coils from the bikes with known functioning ignitions....  Same result, no sparky...   What am I doing wrong???  I used to charge capacitors like that all the time in shop class, and I KNOW it worked then...    

Thanks in advance,

Fabricator (Apparently not an electrician)

[chickenman_26]

The condensers are rated in microfarads, not ohms. So you really need a capacitance checker to test them. You can get a rough idea of whether they're working with an ohm meter, but they need to be disconnected from the coils. Positive lead to the wire, negative to the condenser case. As the condenser is charged by your meter's battery, the resistance should increase. Don't worry about no spark when you discharge them. There isn't enough charge in them to do that. The coils should test normally after you disconnect the condensers, primary wires, and the spark plug wire. Just a thought - if you have no spark from either coil, check the functioning of the kill switch.

Stu

[Fabricator]

Stu,
 
Thanks for the reply.  I did disconnect them from the coils for all of the tests I described.  Additionally,  I read about the capacitance meter in an archived thread, but do not have access to one.  The cost of a pair of coils from Parts-n-more is not high enough to justify another tool just yet    Just out of curiosity, why would Clymer book suggest that I should attempt aresistance reading, much less attach a value to it?  They also suggested the "hillbilly spark test" as well, and admittedly, I was surprised that it did not work.  Does anyone know if resistance valuers could be successfully obtained with an analog meter?

Fabricator

[Steve F]

As far as I'm concerned, take any of the information in the Clymer manual, and compare it with the Haynes and draw your own conclusion. 
I was wondering since you mentioned that you disconnected the condensors to check them, when you reconnected them, did you make certain that the connections to the points plate were insulated properly?   It's possible that you have the wires short circuited to ground if the wires are on the wrong side of the little phenolic washers.
Just a thought....
Steve F

[Trav-i]

Hey guys thanks for the info.  But i think i'm just gonna start over with some new points and condensers.  The ones that were on my bike were scavenged from some of the other motors we have laying around, none with points covers and sat outside exposed for years.  I did that just to see if the motor was any good and just never changed them because I'm lazy and they seemed to work.   So i'm just going to rebuild the ignition and see what happens, it can't get any worse can it?

Travis

[Fabricator]

Steve,

   Thanks.   The Haynes manuals are rotten, but I did not think the same about the Clymer.... T'ill now.  FWIW, the little "garrolite" insulators were properly installed (Bushing and washers), but as Travis mentioned, the entire ignition system has been neglected.  He is doing the right thing by replacing the parts.    I am just one of those curious types that want to know exactly how to diagnose the condition of a particular part; even if the new parts are sitting in a box on the floor nearby.  Unfortunatly, it sounds like the condensers are not something that can be properly checked with a basic multi-meter.  One last stand for measuring here: Has anyone ever measured ther resistance with a good analog meter??? (I unfortunatly sold my "Simpson 206" to a co-worker, when I left the industrial maintenance field 8 years ago...)  Thanks as always for the replies!

Fabricator

[Fabricator]

YES SIR, thank you a lot.  I was hoping to find something simple that would allow me to do more troubleshooting, prior to "throwing parts" at the issue.  Can I buy you a beer? 

Kindest regards,

Fabricator