Author Topic: Dynatek install and popping sound (Read 2474 times)

Sething · « **on:** January 12, 2019, 03:58:27 pm »

I recently installed the Dynatek electronic ignition on my 1978 CB750K and it starts well. However, when I turn the red dial on the right handlebar switch to RUN before starting, I hear a popping noise coming from the wires connections where I connected the blue, yellow, and red wires and there is some slight smoke rising from the area. The red wire was an addition that was in the instructions that wasn’t there on the original points. The red wire is connected to the Blk/white wire that runs between the points and the handlebar run/kill switch . I’m wondering if the new red wire is where the popping is coming from and if this wire is even necessary.
Also, the m unit freaks out when I rev the throttle. It also won’t idle ( which could be a different issue).
Any ideas on how to stop the

Honda 1977 CB750K

Scott S · « **Reply #1 on:** January 12, 2019, 05:17:23 pm »

Don't turn the red dial on the handle bars.

Seriously though, sounds like you have wires shorting to ground somewhere. The B/W wire to the coils is hot. When you turn the "red dial", also known as kill switch, you are supplying power to that connection.
Check and make sure you don't have bare wires around the connection.

Hopefully you haven't fried the Dyna or M-Unit.

Sething · « **Reply #2 on:** January 12, 2019, 05:58:48 pm »

After doing some research, the red wire supplies the power to the electronic ignition and is required for it to work. I’ve used the splice connector that was given which may be part of the problem and should splice with a connector and solder.

Honda 1977 CB750K

scottly · « **Reply #3 on:** January 12, 2019, 06:05:41 pm »

Quote from: Sething on January 12, 2019, 03:58:27 pm

there is some slight smoke rising from the area.

Smoke is bad!!

The red wire supplies 12v to power the Dyna; it is required.

Sething · « **Reply #4 on:** January 12, 2019, 06:16:44 pm »

You’re right. I need to determine exactly where the sound and smoke is coming from when I turn the switch to RUN. It’s coming from the general area of where the red, blue, and yellow switch are located and I need to do more investigation.

Honda 1977 CB750K

540nova · « **Reply #5 on:** January 12, 2019, 06:23:57 pm »

Follow the smoke.

Sent from my SM-G955U using Tapatalk

scottly · « **Reply #6 on:** January 12, 2019, 06:27:35 pm »

Is the smoke from under the gas tank where the red, blue and yellow wires are connected to the coil wires, or where the Dyna is mounted on the right side of the motor? Be Very, Very careful testing, as letting the magic smoke out of electrical components is lethal.

HondaMan · « **Reply #7 on:** January 12, 2019, 07:01:36 pm »

...and smoke near gasoline can be fatal!

Sething · « **Reply #8 on:** January 12, 2019, 07:32:07 pm »

Something I just thought of: the Dyna needs 12V running to the red wire, and doesn’t necessarily need it connected to the coil wire. What if I just ran the red wire straight to the m unit AUX where it would get power when the key is turned on?

Honda 1977 CB750K

scottly · « **Reply #9 on:** January 12, 2019, 08:22:49 pm »

Quote from: Sething on January 12, 2019, 07:32:07 pm

Something I just thought of: the Dyna needs 12V running to the red wire, and doesn’t necessarily need it connected to the coil wire. What if I just ran the red wire straight to the m unit AUX where it would get power when the key is turned on?

Honda 1977 CB750K

Both coils also need to get +12V on the black/white wires. My best guess is that one of your coil black/white wires is shorted to ground. If this were a stock wiring harness, the 15 amp main fuse would blow when the kill switch was switched to run, but the m-unit may allow more current to flow before detecting an over-current condition, allowing the smoke.
We can only guess how you have wired your bike...

Sething · « **Reply #10 on:** January 12, 2019, 08:35:45 pm »

Would that also explain the m unit freaking out and the power drop when throttling up to rev the engine?

Honda 1977 CB750K

scottly · « **Reply #11 on:** January 12, 2019, 08:48:08 pm »

Quote from: Sething on January 12, 2019, 03:58:27 pm

Also, the m unit freaks out when I rev the throttle. It also won’t idle ( which could be a different issue).

Honda 1977 CB750K

Won't idle may mean you are only running on two cylinders...

Sething · « **Reply #12 on:** January 12, 2019, 08:53:37 pm »

Thank you Scott. Good idea at this point is to check both coils and see if one of them may be bad. I’ll do that asap. That would explain a lot.

Honda 1977 CB750K

scottly · « **Reply #13 on:** January 12, 2019, 09:03:27 pm »

While you're at it, check to see if either of the coils black/white wires is shorting to ground though the aluminum coil mount. Have you messed with the coils and their mounts?

Sething · « **Reply #14 on:** January 12, 2019, 09:24:19 pm »

The coils, the mounts, and the wiring coming out of them are original. I believe I’ve replaced everything properly but I’m going to check all the connections around the coils.

Honda 1977 CB750K

Sething · « **Reply #15 on:** January 13, 2019, 08:23:17 am »

Checked the ignition coil ohms:

Coil 1,4: primary leads 4.6 (healthy)
Secondary leads: 34.5 with plug boots attached; 14.7 without plug boots
Plug boots alone: 10.4

Coil 2,3: primary leads: 4.6 (healthy)
Secondary leads: 14.0 without plug boots attached (healthy) plug boots alone 10.6
36.3 with plug boots attached.

I was able to get one reading for the #2 boot but then could not get a reading after the first try so I think that boot may need to be replaced.
The resistance on the secondary leads seems high but I haven’t been able to find the proper range in my shop manual. I was able to find 3-5 on the primary online.
I’ve read somewhere it should be 24-25k so mine are out of range with the boots on. Having one bad spark plug boot doesn’t explain all my issues.
I’ve also read that even with good continuity the coils could still be faulty.

Honda 1977 CB750K

Sething · « **Reply #16 on:** January 13, 2019, 02:08:11 pm »

Is there supposed to be a spark through the spark plug wires when I turn the kill switch from OFF to RUN?

Honda 1977 CB750K

Don R · « **Reply #17 on:** January 13, 2019, 03:26:08 pm »

Yes, I've been told they will do that.

Sething · « **Reply #18 on:** January 13, 2019, 03:53:02 pm »

Ok, interesting. Once I detached the caps from the plugs and turned on the run switch, the popping wasn’t there or any smoke and the voltage going to the coils and Dyna ignition were all at 11.8.
Well, I’ve gone ahead and purchased a new replacement kit with coils, wires, and plug caps. I had one dead plug cap anyway and I think the coils are 42 years old.
Thanks everybody for the help.

Honda 1977 CB750K

TwoTired · « **Reply #19 on:** January 14, 2019, 11:16:48 am »

Your old coils are likely fine. A 15K ohm secondary resistance is pretty normal. There is 15,000 turns of wire in them. (that's why it's called a coil) Wire has resistance. Age doesn't matter, as metal stays metal so long as corrosion and water stay away. The coil was encapsulated by the factory to prevent metal deterioration as well as its internal insulation. Keep the away from hatchets and it works for several human lifetimes.

The molded in leads can become a problem if mechs aren't careful with bending them too close to the join. This can breach the coil encapsulation seal.

The Dyna-s powers up in spark delivery mode and draws power all the time. The timing circuit very briefly interrupts that mode during crank rotation to produce repeating spark.

If your plug cap is intermittent, it is best to replace them, as there can be a small gap inside them. Spark still happens because it is just another gap to jump for the spark energy along with the ones at the two spark plug tips. At least until all the gaps get way too big.

Cheers,

Sething · « **Reply #20 on:** January 14, 2019, 08:24:35 pm »

Thank you twoTired for the additional help.

Do you have any ideas on why the m unit would freak out and I’d lose my dash lights when I throttle up?

Honda 1977 CB750K

TwoTired · « **Reply #21 on:** January 14, 2019, 08:32:09 pm »

Quote from: Sething on January 14, 2019, 08:24:35 pm

Thank you twoTired for the additional help.

Do you have any ideas on why the m unit would freak out and I’d lose my dash lights when I throttle up?

Loose connection, Power or ground path seems likely if you aren't blowing fuses. What fuse block are you using? Throttle up changes the engine vibration frequency.

Wouldn't hurt to check voltage level. But, I don't know how sensitive the M unit is to voltage variance.

Cheers,

Sething · « **Reply #22 on:** January 14, 2019, 09:40:08 pm »

I’m running an m unit v2. Electrical is foreign to me so I’m learning. The voltage while not running seems ok when the power is on. I’m worried it may be a problem with wiring elsewhere. Once I have the new wires and spark plug caps on with the new coils I will need to see where I’m at. I’ll test the voltage with my multimeter at the m unit and elsewhere. At this point I’m lucky it even started.

Honda 1977 CB750K

Sething · « **Reply #23 on:** January 20, 2019, 11:06:58 pm »

I finally determined what the popping sound was and it was the carburetor intake filter pod on carb #4! I have K&N pod filters. Scared the heck out of me the other day. I turned the kill switch to RUN and it popped and a little puff of smoke came out of the carburetor air intake pod filter. My guess is that the spark that is going from the ignition coils to the spark plug is causing the pop and igniting the gas when I turn the red kill switch to RUN and bring power to the ignition coils. I still don’t quite understand why there is a spark from just turning the red kill switch from OFF to RUN.

Honda 1977 CB750K

robvangulik · « **Reply #24 on:** January 21, 2019, 02:43:32 am »

Why do you use the kill switch anyway? That is only meant to be able to switch the engine off in an emergency without taking your hand off the handlebar, and it'll wear a lot faster than the keyed ignitionswitch!

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Author Topic: Dynatek install and popping sound (Read 2474 times)