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Dyna III trouble, coils, or?

Sahms

Sahms

Cruisin' Guzzisti
GT Contributor
Joined
Oct 27, 2008
Messages
116
Location
Knoxvegas, TN
So I recently got a 77 LeMans 850 back on the road after a 22-year sleep. The bike had a Dyna III installed, so I left it in, and it sparked both cylinders (although the spark on one side may have appeared a little weaker than the other). I checked and cleaned all the conectors and went thru the distributor, and timed it dynamically.

The coils that came on the bike were some generic-looking ones and they were horribly corroded. They measured about 4 ohms. I swapped them for some OEM Guzzi coils I had laying around that Chris Collins sent me that measured 3.4 ohms.

The bike starts right up, usually on the bump, but after a long ride wants to die at idle and then doesn't want to restart, maybe one cyl worse than the other. Let it sit five minutes, not even enough for the motor to cool, and it starts right up on the bump and settles into a perfect idle again.

The motor's fresh, and compression is 175-180 on both cylinders. Jetting is stock and the plugs look ok, although after a 100-mile ride Saturday they had a little dark spot on one side, and one was a little darker than the other.

No smoke, and the motor sounds fine.

I gather the "normal" Dyna failure mode is a cylinder dropping out. Does this sound like a coil failure? What's a good coil to use other than the Dyna black coils (which are now the recommended coils per Dyna over the greenies, I think)?

TIA
 
Fred,

This does sound like a coil issue. If you have a foreign car parts handy, the stock 12 volt coils for a VW beetle (the original one) should work just fine. In the 80s, I even used the blue coils you could get at Walmart at that time.
 
I know this is an old thread now , but when I first got my T It would only run for about 5 mins before dropping one pot, this I traced to the module ( dyna lll) Before replacing the module I did check with dyna , that it would run with the standard 3.5 ohm coils,they said yes , but no would have been more correct . Both the coils and the module got to hot to touch in only min's. I then see in the box it came in, a bit of paper with the bad news , coils must have at least 5 ohms. Being a tightarse I fitted a ballast resistor to each coil which fixed it but in the end I got pissed off with all the crap accumulating under the tank and coughed up for the 5 ohm coils. The thing is that neither the original module or the coils got hot , it just dropped that one pot . Without getting to technical this must have summat to do with the dwell angles ( I dont have a dwell meter ) :)
 
I think you need to get a new coil and coil pack. I think that's where the problem starts and a new coil pack will solve this.
 
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