Topic: I got 99 problems and a coil failure is all of them.

[Shenanigans]

Since I cant really ride it around to get it hot I put a heat gun on the Dyna-S triggers and sure enough after a min. they start causing the engine idle erratically then the motor dies. Once it dies, the bike can not be restarted right away. It just backfires and after a couple of mins of letting them cool the bike will start again.

I remember Hondaman saying something about triggers getting electronically leaky when they heat up. I am going to re-time the bike right now then test it again just to double check. I think I can hold a multimeter, heat gun and timing light at the same time?


So I think the verdict is my Dyna went south...

This is the classic scenario of the trigger failure.
The heatsink compound only improves the heat transfer about 3%-5% over not having it there at all: it's not a big difference, but since the desing has always been near the "ragged edge" thermally speaking, it adds a little insurance for the designers.

Once the triggers have been heat-damaged (by whatever originally caused it), they won't go "back" again. They will always act the same: OK when cold, erratic and too much timing advance (at idle) when hot. Eventually, they will short altogether, causing weak or no spark.

I have mostly seen this happen when the bikes had 3-ohm coils, either Dyna or Accel coils, without Dyna's recommended inline resistor. (Not that they sell one: they don't, never have.  )

Ouch, those are the exact symptoms I seem to have and what do you know, 3-ohm coils. I retarded the ignition enough to where when it does warm up and start to wander (timing wise) it will not go far enough to kill the bike but there is nothing above 7000 rpms. As long as it can get me the 7 miles to my truck tomorrow morning before work, I am in the clear.

I read a couple of reference to to the Dyna III box, or something like that. I think I have one on a parts bike, I dont know exactly what it does but can it be of any help?

And HondaMan, take care of my motor when she finally arrives.

If you have a working Dyna II module, and some good Dyna S triggers, you can connect the triggers to the III box, then connect the III box to the coils. The triggers then switch the box (much like mine) and the box switches the coils. The III box is rated for up to 6 amps, IIRC. They were notorious for short life, by when Terry in AUS sent his in for "repair", they sent him a new one for $50, not bad. I once got a drag bike 750 in a basket: it had 3 Dyna III modules, all dead, in the midst, and a set of 3 ohm coils. 

Did you already send that Four? I'm just tearing into another 750, so if it is to be rebored I could take the cylinders to the shop together. When I take them 3 or more sets at once, they sometimes give me a discount, depending on how busy they are or how fast I need them.

Eh, if its they were that notorious for going bad I think I am going to leave it alone!

As for the motor, I cant ship it out until sometime after the 25th-ish aka payday and when all the other part should arrive to me.

[HondaMan]

Okie-doke.
Are we talking Gentleman's Express rebuild?

[Shenanigans]

GODDDAAAAMN IT. About a month ago I got a new Dyna-S and it worked fine. Last night one of the pick ups failed. again. Hondaman can I please buy one of your ignitions?

[HondaMan]

GODDDAAAAMN IT. About a month ago I got a new Dyna-S and it worked fine. Last night one of the pick ups failed. again. Hondaman can I please buy one of your ignitions?

Man, you're having the worst luck with Dynas - kind of like the local SOHC4-ers around the Colorado Front Range area. I wonder if Dyna is having a quality bug of some kind? In this economy, I have been seeing quite a bit of that in the Industrial Electronics sectors, like PLCs, servo control modules, and the like.

I've got several Ignitions on hand...mgparis@concentric.net .

[Shenanigans]

GODDDAAAAMN IT. About a month ago I got a new Dyna-S and it worked fine. Last night one of the pick ups failed. again. Hondaman can I please buy one of your ignitions?

Man, you're having the worst luck with Dynas - kind of like the local SOHC4-ers around the Colorado Front Range area. I wonder if Dyna is having a quality bug of some kind? In this economy, I have been seeing quite a bit of that in the Industrial Electronics sectors, like PLCs, servo control modules, and the like.

I've got several Ignitions on hand...mgparis@concentric.net .

My first assumption about the S going out, given the circumstances, would be that there is something wrong with the bike causing it to die. However the first one lasted 12000 miles and I have not changed anything. I dont even know what would cause it?

[Shenanigans]

I guess I should put it out there how they died (again) and the symptoms. I am not too happy right now. I was on the freeway cruising along fine at about 1 am. Got off and went a few block then the bike started backfiring horribly from 1 and 4. AKA flames out the back. Got the two miles to my house and 1-4 were completely dead. I switch the signal wires and the plug wires between 1-4 and 2-3. Had spark on 1-4 but 2-3 dead which eliminates the coil. Checked the valves to make sure there was not something horrible wrong, found nothing.

Next day I went to start it up again and its still running on 2. Not like before when it would fail after getting hot.

WHY.

[scottly]

Can you swap the pickups to isolate them from the control box, or will the Dyna harness not allow this?
As far as if something about your bike causing the failures, make sure that your charging voltage isn't too high, and the ignition has a good ground.
If it turns out that the box is failing, rather than the pick-ups, is it mounted such that it gets a good supply of cooling air? (The box above the rear tire in my avatar is my Gerex ignition box.)

[Shenanigans]

Can you swap the pickups to isolate them from the control box, or will the Dyna harness not allow this?
As far as if something about your bike causing the failures, make sure that your charging voltage isn't too high, and the ignition has a good ground.
If it turns out that the box is failing, rather than the pick-ups, is it mounted such that it gets a good supply of cooling air? (The box above the rear tire in my avatar is my Gerex ignition box.)

On this bike I just have the Dyna-S. Its not like the Dyna 3 which has the control box. There is nothing on it BUT the pick ups. So its pretty simple. You dont have an extra point plate laying around do you?

I guess I could swap out the failing one with the other good pickup from my last set. 1/2 plus 1/2 equal 1  

[scottly]

As I mentioned at the start of this thread, I'm ignorant about Dyna. If the electronics are built into the pickups, then I would have to say the design sucks! Silicon does not like high heat, such as found on the side of an air-cooled motor, in the desert!!
I might have a spare point plate, but after following your problems, I need to make sure I have 2 spares before I give one up!!! Do you need an advance/point cam as well?

[scottly]

Just dug through some boxes: I have 2 750 points plates!!! Only found 1 advance/cam, but if you need one I will look some more tomorrow.

[Terry in Australia]

Send that Dyna S back to Dyna mate, and they'll test it and replace it if it's buggared, free of charge. As much as I love my excellent Hondaman ignition in my stock as a rock CB750K0, I also love my Dyna S ignitions in my K1 and K2, not to mention my superb Martek 440's in my F2 and my Suzuki GS1000S. I've got a rare Gerex multi-fire ignition like Scottly's too, I might hook that up to my CB1060cc RC engine I'm currently building.

I'd never heard of a Dyna S failing until I became a member of this site, except for a couple that had the pickups ground off in crashes. Most "faulty pickups" I've come across have just been incorrect gapping between the pickups and the rotors, or bent rotor bolts causing the rotors to grind the pickups to death. Regardless, as Mark mentioned about my earlier experience with Dyna, they have an excellent reputation for after-sale service to it's customers. Cheers, Terry.    

[Gonzowerke]

The picture you posted of your triggers seems to show another problem you have. Judging by the streak on the cam and the scuffing on the inside radius of the one you have removed, you are having contact between the cam and triggers. You should have just an air gap.
You can buy heatsink compound at any auto store. It is with the permatex stuff.

[crazypj]

You can get thermal grease from anywhere that builds/sells computer parts, they use it on CPU heatsink.
Bad grounds (and overheating) will kill electronics in short order
 You can easily get over 100v on trigger wires. (primary peak volts, not going to explain, look it up)
 I've seen over 300v on some systems (Suzuki VS800, 318v while running)
 You need a peak volt adapter on meter to check
 Check ALL grounds, including engine to chassis

[Spanner 1]

+1 with Gonzo.... that trigger sure looks like it's been in contact with the cam..... = no worky.

[Shenanigans]

I have since replaced that magnet. I was about 400 miles in on my last trip when I realized it was hitting the trigger. It worked fine for the rest of the trip however but I put a needed to put a new one on anyways. I am going to try and re-space it again. The Arizona summer is the best time to work on the bike outside in the sun.

[ofreen]

As I mentioned at the start of this thread, I'm ignorant about Dyna. If the electronics are built into the pickups, then I would have to say the design sucks!

You could say that, but it doesn't make it so.  They are very reliable.  They will generally outlast the bike they are installed on.  As I've just mentioned in another thread, the Dyna S in my 750 is over 20 years old with over 93,000 miles on the ignition and it has been flawless.  That includes 16 summers in southwestern Idaho, plenty of running in temps over 100F. 

[Terry in Australia]

Yep, I agree with Offy, my Martek in my F2 has outlasted 3 CB750's over it's 30 year life, and still throws a big fat spark, and I've had Dyna's just as old work just as well. Cheers, Terry.

[BLUE71TURBO]

 Terry and Ofreen, sounds like yours are from the stone age when things were made better.     But as HondaMan
stated with the new production one's there seems to be major problems.  I run a magneto so i don't have these problems
but i was wondering can't you use an electronic setup off of a later cb750 on an early cb750 ?   Like on the later model Kawasaki's  ignitions on the early 900's and 1000's .   

[Terry in Australia]

I've got a new(ish) Dyna S in my K2 with the F2 engine, and it's working fine, even after the bike was dropped hard on it's right side @ 60 MPH, crushing the points cover into the pickups, so I don't know, I reckon they're pretty indestructable.

I have heard of newbies killing electronic ignitions by connecting power wires up to the signal wires, I know at least one newbie who did that on a Martek and killed it. (me.........).

Clyde Ikin in Sydney converted a later DOHC 900 ignition to work on his SOHC CB750 and he was pretty happy with the results, but I had a CB900F and thay were known for ignition failures, so I wouldn't recommend them.

Of course, there have been plenty of OEM electronic ignitions built for 4 cylinder bikes since the dark old days of the first DOHC Honda four's, so I'm sure there's something that could be used, but for my money, I wouldn't dick around with all that stuff, I'd just buy a Dyna 2000 system and drag myself into the 21st century..........    

[scottly]

I personally have no issues with modern electronics, but I believe that those bits of silicon should be kept as cool as possible, not mounted on the side of an air-cooled motor, under a cover. 

[Terry in Australia]

My wife bought some silicon bakewear recently, apparently it can safely withstand temps up to 800 deg F, maybe the pickups should be made outta that stuff?

[scottly]

Naw, her stuff is silicone, not silicon.

[Terry in Australia]

Oh, ok mate, 'scuse my ignorance, what's the difference?

[scottly]

Silicon is a semi-conductor, when "doped" (purposely contaminated) with other elements. Silicone is the stuff they used to use for breast implants....

[Terry in Australia]

Silicon is a semi-conductor, when "doped" (purposely contaminated) with other elements. Silicone is the stuff they used to use for breast implants....

So you're saying that the breast implants I bought the wife aren't gonna make her any smarter? Woohoo!