Topic: Dyna or electronic ignition pick up testing

[halllzy]

Hey all, I sent this to the Dynatek team too but wondering if anyone here has any advice?

Just wondering if you have instructions for testing the pickups individually in a dyna 3 ingnition? My CB750 is not firing in 2/3 cylinders; I've verified spark, ohm tested coils (@ spec), cylinders are getting gas, the only problem is static setting advance. 1/4 pickup V is dropping right at the F mark for 1/4 (next to TDC), there is no voltage drop at all when testing 2/3 cylinders anywhere in the crank cycle. It was running fine a week ago; no change in wiring and I've verified all connections are tight and correct as per installation instructions. Any help would be appreciated.


... not sent to Dynatek; the PO installed the Dyna 3;
When conducting all the testing I had to replace the spark plug caps (1 had a chunk out of it that was taped over, another had an interesting "rain stick" sound), trimmed the wires 1/4 inch and got the new caps on fresh tips.  Couldn't figure out my no spark problem with the new caps, resolved by replacing all 4 spark plugs; started her up but not a great idle as 2/3 cylinders were not firing (cold pipes, good gassy smell when i pulled plugs after a 5min idle).  Old plugs looked great (not lean or rich) prior to the problems.  Compression is 134/5 across the board.

1975 CB750F0 stock carbs, airbox, exhaust (minus the insulation in the back 1/3 of the muffler which blew out a few months ago)
Stock coils; test on primary and secondary for both are spec (5ohm primary / 23k ohm secondary through plug caps).  I was concerned that one of the spark plug wires may have broken right next to the coil body, but the testing is all coming out gravy, even when moving that wire around a bit.

I'm not a circuit board kinda guy (points plate/assembly ordered this morning), but I'd like to try to determine if the dyna is shot.

Cheers

Mike

[madmtnmotors]

I have the original installation instructions from my Dyna III that I can refer to if necessary. I have had the "Black Box" fail once, and found a used one on ebay that actually worked. Dynatek does not make the Dyna III for the CB750 any longer and cannot provide replacement parts. It sounds like something has failed, either the trigger of the controller (black box). Either way, you will either have to find a replacement part for the failed component or replace it with something else, either another electronic ignition or the original points and condensers.

You can narrow it down to either the pickup or the black box by switching the blue/yellow leads between the pickups and the black box, PLUS switching the blue/yellow at the coils (you have to switch leads at both locations, you can't do just one). If 2 and 3 stay cold then the pickup is bad. If 1/4 go cold then the black box is bad.

I can scan the original install instructions if necessary. I believe it includes troubleshooting steps, but if you follow the instructions I've given then you should be able to narrow down the culprit.

[halllzy]

Good advice on testing black box vs pickup; I've got scans of the original instructions.  Dynatek sent me a reply.. didn't think it's been 20 years since they've sold the dyna 3!!

They sent me a list for parts for the S; i guess some may be interchangeable, but it looks like points will be the way to go in a week or two when the setup arrives.  The PO did a wicked tape job when it was installed.. will need to think about unwrapping everything.

[madmtnmotors]

it looks like points will be the way to go in a week or two when the setup arrives.

Does this "setup" include the points cam? The points cam is removed when any electronic ignition is installed. The advancer typically remains, but the points cam had to be jettisoned...

Make sure you follow the manual when installing the points cam since it can be installed 180 degrees out. 

[Jerry Rxman Griffin aka MuthaF'er]

Wilbur, last time I spoke with Dyna I was told they would rebuild a 'black box' if needed. They actually sent me a resistor gratis when I told them I was having voltage issues with the III and the 3ohm coils (never installed it yet) which is why I called looking for information.

[halllzy]

I've only ordered the point plate, points and condensers so far as I got em all for $10.  Going to survey what else is needed today; thanks for the heads up!  The parts list in manuals on the forum has been invaluable.  They seem to be the same part #'s on the k4,5 &6 so hopefully findable
That is if I can't work some voodoo on the dyna.

Sent from my Nexus 6P using Tapatalk

[halllzy]

MADMTNMOTORS box vs pick up test was a success!!  unwrapped what seemed like a whole roll of electrical tape from the wiring; switched the wires up as per your direction and both pickups worked perfectly; put everything back to spec and it all works perfectly.  I'm guessing the white wire from the plate to the box had a bad connection.  I still have some new locking connectors so fit one for a better connection and put it all back together.  Static timing is set, now I just need to get the airbox back on and balance the carbs (again).

Thanks for the help!

Still have points plate in the mail and will have some time to find the cam for a back up plan if the dyna kicks the can.

[madmtnmotors]

MADMTNMOTORS box vs pick up test was a success!!  unwrapped what seemed like a whole roll of electrical tape from the wiring; switched the wires up as per your direction and both pickups worked perfectly; put everything back to spec and it all works perfectly.  I'm guessing the white wire from the plate to the box had a bad connection.  I still have some new locking connectors so fit one for a better connection and put it all back together.  Static timing is set, now I just need to get the airbox back on and balance the carbs (again).

Thanks for the help!

Still have points plate in the mail and will have some time to find the cam for a back up plan if the dyna kicks the can.

LOL! My suggestion was to determine whether the pickup or the black box was faulty. Inadvertently discovering a bad wiring connection makes the troubleshooting that much sweeter when the problem is corrected, even if it is by accident, it still counts! 

I'm reminded of the monkeys and the typewriters analogy every time something like this happens... 


https://en.wikipedia.org/wiki/Infinite_monkey_theorem