Faulty Dyna S

[Guest]

haven't touched my bike in a few months, last i had it running i had just replaced a dyna that was replaced under warranty buy dyna for faults. Bike ran better than the first system but still failed to idle once warmed up and would stall at lights. Will start back up but maybe backfire a few times trying to get it going. Trying to figure out if im dealing with another faulty system or possible faulty coils. Can anyone suggest results to building a ignition system using older GM HEi modules? Ive done research on that being an option and would like feedback from anyone who has used this setup. Thanks!

[Nessism]

The Dyna S has some issues but what you describe would be very rare. Seems unlikely to get two bad systems. Oh, and the stock coils are quite reliable overall. Biggest issues with them are bad plug caps, deteriorated high tension wires, and main harness voltage drop on the line feeding the coils. All issues that can be resolved.

[Gumpster]

I had a charging system that was overcharging and damaged a Dana s and a Dana coil over time. Did a voltage test and if I recall, it was 17v. Replaced the defective regulator and no problems since. It's an easy test and might reveal the root cause.

[Chuck78]

Definitely sounds like other problems. Check your charging voltage at the battery first with the bike running as stated above. Shut the bike off, pull the gas tank off, and figure out where you can check the voltage at the ignition coils and at the Dyna power wire.

Start the bike up, it will run for about 35 or 40 seconds from the gas in the fuel bowls ( make sure to plug the vacuum hose that went to the petcock, so the carbs don't have a massive vacuum leak!). Now test the voltage at the coils, it's the orange wire on all of my GS models which are all 8 valve. Test how much voltage is going to the Dyna also. This is often the biggest problem with ignitions in general, and also getting low voltage to the Dyna-S will kill it without a doubt! They cannot survive for the long-term with less than 11 volts, they strain themselves to death.

Also, if you have not replaced your resistor caps on the ends of your spark plug wires, replace the entire assembly with new NGK parts, and if you have plenty of plug wire to spare, snip off 3/8 or 1/2 inch from the end of the original factory resistor caps off of them. The biggest problem with the factory coils is that you cannot replace the wires easily, they are permanently attached to the coils.

How did the bike run before you install the Dyna? Or did you ever get much riding time in on it? Or was it just a project bike and you are just now getting it running for the first time under your ownership? Don't rely on what previous owners say!

[Chuck78]

Bike ran better than the first system but still failed to idle once warmed up and would stall at lights. Will start back up but maybe backfire a few times trying to get it going. Trying to figure out if im dealing with another faulty system or possible faulty coils. Thanks!

Sounds like you should tear your carbs down, give them a good cleaning, inspect the float needles very thoroughly and replace if they are worn, and reassemble them and properly adjust the float Heights. It's possible your carbs are flooding. Have you done any sort of spark plug readings, especially after the bike is stalling out?