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Backfiring persists after 1 year sitting

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baloo:

--- Quote from: redrider90 on September 16, 2025, 01:15:00 PM ---
What kind of ignition do you have. Some 89s came with Moto Plat like my 90 mille. ....

--- End quote ---

I just get 10 minutes a day to work on the Guzzer, so please bear with me and my ignorance and erratic learning curve...
PLUS, lately, I have been taking The Stupid Pill (not a prescription item, and not available over the counter -- and definitely age-related) such that I completely unlearn decades of experience working on cars/bikes!!

I have spent an unnecessarily inordinate amount of time going thru digital workshop manuals on other Guzzi models that I downloaded, searching for just basic pics of the engine with component labels -- of which there are NONE.  Yes, I have probably hours spent in this endeavor.

1.  I was hunting for the distributer, and, DON'T TELL ME THIS IS IT, (see attached pic) buried under the gas tank and tucked inside and under the frame, and out of easy reach and easy adjustment!!??  Whaaa?  I see no exiting plug wires, but are they hidden on the other side?






If that's really the dizzy, I have lost all respect for the Guzzi engineers -- they're like the 60s-80s American car designers who NEVER worked on the actual cars that they designed, resulting in impossible access to high maintenance items such as plugs, starters, etc!


2.  Also, what is this a finned piece behind the right side cover?  It looks like a rectifier.






3.  Lastly, in my notes from 5 years ago and previous notes from the previous owner from back in 2007, there is a hand written annotation that a "Dyne" was installed (spelled like that).  IF THIS IS referring to a Dyna ignition, WHERE would I find this box?

4.  No, another "lastly":  how in the world do I remove the air filter element without removing the gas tank?

Thanks.

redrider90:
OK that is the Dizzy. If it you a Dyna III electronic ignition in it then you have a points Dizzy that has the points removed from it and replaced it the Dyna pick up unit. The Moto Plat Dizzys could not used to accept the Dyna. There should be a single CDI unit tucked in behind the rectifier sitting in front of the battery. At least that is where I put mine. Dyna has 3 ohm (green) and 5 ohm (black coils). I managed to fit mine in the stock coils placement. I found 2 types of experiences with Dnya. those who never had any trouble out of them and then those like me who have had trouble with failures. I have had one module failure and 2 coil failures. If you do have a failure you can return them to Dyna for testing and even if out of warranty they will charge a lower cost for replacement. 
As replacement of air filter ( I run high flow K&N the fits in the stock box) you have to remover the battery to get at the rear of the box that has 2 long screws holding the back plate on the box and replace it from there. 

paulbricey:
"I have spent an unnecessarily inordinate amount of time going thru digital workshop manuals on other Guzzi models that I downloaded, searching for just basic pics of the engine with component labels -- of which there are NONE"

TBH the Parts Lists are a lot more useful when looking for components & assembly sequences/locations.

John Croucher:
Pull the mixture screws and spray carb cleaner in a couple of shots.  A lean mixture can cause backfire when off throttle.  Slightly dirty can lean out mixture.

wirespokes:
Sounds like you have a Dyna. They're known to act up if there's the slightest amount of corrosion on the boards.

The distributor may look like it's in an awful place, but where else can it go? The engine was actually designed many years before the V7 in 1967, in which it was first debuted, for a military vehicle, and possibly a fiat. it's actually not that hard to deal with. First, remove the tank. The two slotted cover screws allow access, and the cover can be removed turning it a certain way. You'll need to remove the dyna board to access the reverse side that grounds to the distributor body. A pencil eraser works to clean it up. Nothing abrasive!

That could handle the problem.

Since the low speed jets aren't gunked up (evidence, runs fine low end)I wouldn't expect it of the midrange. If working on the Dyna doesn't get it, then ensuring all electrical leads to the coils and ignition are bright and shiny would be my next step.

But my best guess is the Dyna.

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