sudden loss of power

[sickradsean]

This one really has me stumped. Recently (this week) at indiscriminate times (after warm up OR during) my bike will act like it is struggling to idle or even exist. Everything will be running smoothly and then a sudden drop in RPMs and it has that really boggy, farty, lack of power . To the point that it'll die if you don't hammer the throttle.

I know the carbs are clean and adjusted/synched. I know the gas is good and stabilized. I've replaced the fuel filter, and cleaned out/ checked the fuel pump. Air box is clear and filter is fine. I have new coils and wires on the way to rule that out (I was going to replace them anyways), but I really can't figure why randomly it feels like i'm down to two cylinders.

The timing wouldn't go out of whack but then sometimes be back in whack.

Stuck float? Crap in the carbs that gets stirred up and then settles in a jet?

[gltriker]

Stock points and condenser ignition still in place? Electronic ignition?

[sickradsean]

Electronic. It's from the PO but from the red wire and clip into the blinker relay I'd say it's a Dyna.

[gltriker]

POST#4

Electronic It's from the PO but from the red wire and clip into the blinker relay I'd say it's a Dyna.

I presume you have a 12volt test light used to set the engine's static ignition timing, and are familiar with the Dyna S modules static ignition timing procedures.
Yes to both questions? Good.
A quick method to observe if the primary windings circuit of each ignition coil is functioning, when the engine is running, is to individually probe both two double female socket terminals. located under the rubber boot. It will not hurt their primary windings ignition circuits to do this running engine probe test.

The low watts, test light bulb will flash at both primary circuits' test points in synchronization with their respective ignition coil discharge events, telling you the individual Dyna S modules are working; internally switching their respective ground path connection, on and off. ( make and break )
If the running engine develops a "sudden loss of power", individually test both primary ignition circuits' double female socket terminals, again.
If no test light bulb flashing is observed on one circuit, that occurrence is very likely caused by a faulty Dyna S module.

edit: added March 18th, 2022, here's the 12volt test light I use for static ignition timing. Nothing special.
A Very low watts light bulb inside the test light, for running engine primary ignition circuits' testing purposes is an important detail, though. Attach the low watts test light's alligator clip to the negative battery terminal

Screenshot_20240618_122339_Gallery.jpg

[sickradsean]

On a side note: when I replace the coils will I HAVE to recheck the timing -or- I SHOULD recheck the timing?

[Sidecar Bob]

Electronic. It's from the PO but from the red wire and clip into the blinker relay I'd say it's a Dyna.

It may not have anything to do with your current problem but I'd recommend moving the Dyna's power connection to the black/white wire that feeds power to the coils. The Dyna ignition draws a lot of current and has no business being connected to the same fuse as the turn signals, brake light and horn.
Not only that but if it is on the ignition circuit it will be turned off when the kill switch is off, which means it won't drain the battery if you are working on something and need the key on.
This can also help when you need to start it with a low battery because you can turn the kill switch off, crank the starter to get the engine turning and then turn the sparks on while the flywheel keeps the engine turning enough to catch.

[BlueThunder]

Dyna ignitions are notorious for one module to die. What you are describing is that one module is "flaking" out. Personally, I would replace the Dyna with something more reliable. I have a HondaMan ignition "amplifier" that uses the points as a low voltage signal to trigger the coils. Points last forever, and I haven't had the need to reset timing in over 5 years.

[ericheath]

An intermittently sticking slide can do this. My first bike would stick if I didn’t run MMO in the fuel. It doesn’t take much to cause one to hang up and when it does that cylinder’s AF ratio is off.

If you pull them, note the cleanliness of the slide surfaces. If they’re dark and dirty, you have an issue. A leaking air box/filter from a bad seal can let a lot of dirt in

[robin1731]

Dyna ignitions are notorious for one module to die. What you are describing is that one module is "flaking" out. Personally, I would replace the Dyna with something more reliable. I have a HondaMan ignition "amplifier" that uses the points as a low voltage signal to trigger the coils. Points last forever, and I haven't had the need to reset timing in over 5 years.

And yet I have a lot, probably over 50 and maybe many more, bikes of my own and customers that have been running Dyna ignitions for 2 or 3 decades. That would include the old Dyna III model along with the new style. On GL's and many KZ's. It is simply not true that "Dyna ignitions are notorious for one module to die".

[BlueThunder]

Sorry but I beg to disagree. Perhaps the ones manufactured recently solved the problem but earlier ones were failure prone. It has been my experience that this is true. Besides, check the various forums (posted dates) for confirmation.

[robin1731]

Yes, because like most things you only hear about the one that goes bad. If they were so bad I would have had to replace many if not most of them over the past 40 plus years. I can think of one in all that time.

[Sidecar Bob]

FWIW, one half of mine died just after the warranty period ended. Dynatek replaced it anyway and the replacement is still working fine 8 years later.
It is a known issue but the wouldn't still be in business if it happened to more than a small percentage of them.

[redglbx]

Using Dyna’s for many years now w/o any issues with the modules. I will say that I did have a set of coils die after nearly 15yrs and Dyna did right by me on those.

Originally I put a Prestolite ignition in my 76 because you couldn’t get the points balanced, I suspect the improperly ground points cam they talked about back in the day but don’t know for sure as the points plate and cam ended up somewhere in the field across from my house.

I put The Dyna in because it was much easier to balance than the Prestolite which I though I was having issues with (didn’t) and it was much easier to set up.

On another note let me add that Randakk for years maintained that doing a “static” timing would over advance the timing by 6-10degrees. I was skeptical but actually checking the timing dynamically with a degree wheel setup on the LH cam gear showed that he was indeed correct. Engine runs much better being timed dynamically, I am a fan and recommend it.

When I can get back to working on my bikes (extensive back surgery) I need to look at my 76 as I’m getting a back fire at idle from the rh side, runs perfect above idle, doesn’t do it until warm though. I suspect a plug/plug cap, anyone had this happen ? Probably won’t get to be able to work on it until after the first of the year. Anyway, I’m a Dynafan!

[sickradsean]

Looked into the ignition and can confirm its a Dyna S. I put some MMO in the gas and oil, did seem to smooth things out for a bit but then the idle drops out of nowhere! After about a min or so it evens itself out again. I could see a sticky slide or float as a possible cause. I had recently drained the carbs and then not run the bike for a few weeks (dumb, distracted mistake). So its possible there is some varnish all up in there.

Still waiting on the new coils and wires. Ill install those with some new plugs and then report back. Still scratching my head.

[MattMcCoy]

My guess would be dirty idle jets, if opening the throttle and increasing RPMs keeps it running.

You might try this to see if it helps:

https://www.motorcycleproject.com/text/ ... _bike.html