Backfire

[blakbird]

When fuel is reduced, exhaust temperature rises. Any previously unburnt fuel in the exhaust may then ignite.

Thank you Mr Zibell.

That makes sense, to a degree .

 

[Chuck Stone]

Ok,

Sorry for the long delay reporting back. Finished another bike repair and went on vacation in the interim.

Per Dynatek's offer, I sent the control Dyna III control unit and green coils to them for testing. The coils tested fine, but the tech stated he had never seen a control unit start to fail after a few minutes in the same way in his 20 years with the company. Given it was 20 years old according to their records, they offered to ship me a new one all in (with postage) for $102.00. Very nice.

Glad to report back, all reinstalled, run and road tested, all is great. No hiccups, etc.

My thanks to the advice, questions and above all, Dynatek for excellent customer service.

Chuck

 

[cobe tun]

While on the subject of Dyna ignition, I am ready replace my 2 canister coils on my 86 LM IV SE
with dyn coil. I have been asking around as to which one? 2 units DC3-1s?

I never replaced the coils even though I switched out the points-and-condenser years ago.
There are 2 port dyna units and 1 port units ...

 

[john zibell]

You have one spark plug per cylinder, so 2 single port coils is best. A BMW airhead could use a single double port, but the ignition timing on a Guzzi just isn't conducive to a single double port.

 

[cobe tun]

Thanks john. Should I get a blue or or Green one? They are both single port. I think the only
difference is resistance rating.

 

[john zibell]

Thanks john. Should I get a blue or or Green one? They are both single port. I think the only
difference is resistance rating.

Good question. There has been some talk that the green ones are not as reliable as the blue or black ones, but I've had a set of the green ones for over 20 years on my Mk V LeMans. Get the resistance rating closest to the original coils, which is the same as the old VW beetle 12 volt coil. I don't remember the resistance rating of the stock Guzzi coil, but if you look up the VW one use that as a go by value. You may not be able to mount them in the same location as the originals. For the MkV I had to make mounts (using available hard points) and place them on the left side of the frame under the side panel.

 

[cobe tun]

Thanks John. I'll look more into VW coil. One of my friend is a VW Beetle nut. I'll reach out to him.

 

[Amboman]

Green Dyna coils are 3 ohm, the black ones are 5. VW coils such as the Bosch Blue Coil are 3 ohms.

 

[cobe tun]

Thanks. Here are the photo of coil I want to replace. I assume they are both 12 volts for i have a 12 volts battery. Correct?

 

[john zibell]

Yes those are 12 volt. You will need to mount the Dyna coils in the same area.

 

[cobe tun]

thank you. I will measure the ohm resistance across the primary winding on the canister coils.
It should read 3 ohms, I hope.
Charlie: I used to own a 71 Ambo back in '77 when I was in high school.

 

[cobe tun]

John

Can I use these as well?
euromotoelectrics.com/12v-Ignition-Coil-Moto-Guzzi-BO-Coil12V-p/bo-coil12v.htm

 

[john zibell]

Yes but they take more space than the originals. The old standby in the 70s and 80s was to buy the blue coils at WalMart tor your bike when the originals failed.

 

[cobe tun]

dang.. Walmart been around that long? All the way back to the 70s?
Indeed. them original coils are pretty small.

 

[MikieZ]

Chuck,

When my 1000 SP was having similar problems, and I upgraded the ignition system, I spoke with Paul Crane of C5 Ignitions. He said to be sure that I had either resistor plugs, or resistor plug caps to avoid burning out the coils. I had no idea that it mattered on an older bike. I had neither prior to having problems. Everything has been good for several years now.

 

[Godfrey]

As soon as I saw your first post, I thought, "bad coils." The Dyna ignition units are, general speaking, very simple and rarely fail in my experience, but coils are stressed parts and fail in just these ways over time. Their performance when cold may differ dramatically from their performance when fully heated up. The only way to test them properly is on a coil testing device, a piece of equipment that very few shops have.

My LMV had very similar behavior once upon a time, and I went through a similar series of inspections and trials. In my bike's case, I found nothing wrong with the fuel system, I added a second ground to ensure that the battery and the engine were well connected electrically, and the bike began to run properly again when I just tore out the old coils and tossed them, installed new ones. Not even Dyna coils, just new Bosch standard 12V motorcycle coils ... like the Dyna was designed to work with.

I never bothered with the Dyna coils on either of my bikes because they didn't use the stock coil mounts, and I'm lazy: I saw no real point to mucking around with the coil mounts, and little real advantage to the Dyna coils... The Dyna trigger and the Bosch coils worked perfectly for the remainder of the time that I owned that motorcycle.