Inrermittent Guessing Game

[OldVet66]

I had two cylinders go out about a month ago. Fiddled with the coil relay and it came back to life normally. It happened again a few days ago, looked at the relay, tightened up one of the female spade connectors that looked if it might have been heating up a bit, and all was well. it happened again yesterday, changed the relay, all was well until the end of the day and it happened again. Limped home on two cylinders. During this time my gas mileage has been off slightly, down from 44mpg to 38-40mpg. Thought that was because of the extremely hot weather we have been having. It doesn't look like the relay has anything to do with it, so what am I going to find when I pull the tank and start tracing the intermittent ignition problem? Is it going to be a Dyna green coil for cylinder 2-3 or a failing Dyna-S Power Module? I'm betting it will start up normally this morning just to make it harder to diagnose. It seems the failure starts after it heats up and has been fooling me when it cools a little bit.

[Agemax]

a good start would be to swap the 2 coils over. if the fault stays on the same 2 cylinders then it rules out the coil.

[OldVet66]

Ha, Dyna recommends switching the Dyna-S output wires in reverse to see if the spark stays on the same cylinders or switches. Same test different method. Either test assumes the fault is constant. Since it has only happened while I am riding that might be a PITA, but the faults are showing up more frequently. I'm hoping yesterdays fault was permanent. I'll know when I start it this morning. I like your test better, It will be easier.

[OldVet66]

This is really turning into a guessing game. I can't get the fault to show up while I am testing without seriously overheating the bike. I had an extra set of Dyna green coils and wasn't satisfied with the way I routed the plug wires the first time so I marked the 2-3 coil as questionable and installed the new coils and wires. I also extended my central grounding to the front of the bike while I was at it. I'll ride locally and see if the fault shows up again. I had a 50 50 shot of solving the problem if it was #2-3 coil on it's journey to breaking down, but Murphy's law being what it is, It's probably the Dyna power module for Cylinders 2-3, that I didn't have sitting on my shelf.

[koolaid_kid]

This is why you should always have a box fan on high blowing on your air cooled motor when working on it whilst running.

[OldVet66]

I have the fans, It's going to take riding this time. The bike makes plenty of power on two cylinders to limp home, but it is embarrassing to drive like that and not particularly good for the bike. Maybe I'll get lucky and it was the coil.

[OldVet66]

Went for a fairly long ride, got fuel, stopped in town and took the local twisty path home, everything was fine. Stopped at a friends house for about an hour. Headed home and Murphy struck at the stop sign just before my house. It is the Dyna-S power module for cylinder 2-3. I'm going to borrow the one off my son's project bike and install it tomorrow. Man I hate intermittent diagnostics.

[OldVet66]

I changed the Dyna DS3-2 power module plate from the project bike bike to mine this morning. She purrs like a Kitty. Set the timing for 1-4 with my old time timing light (clip on, no induction module). Checked 2-3, it was off. It appears the PO from the project bike never attempted to slip the 2-3 module so it was timed on the mark. Both are dead on at idle and hit the advance mark properly. TIME TO RIDE!

[OldVet66]

I just got off of the phone with Dynatech. My unit was years out of warranty but they still gave me a RMA # to replace the Power module plate for cost which is substantially less than a new kit. I love businesses that stand behind their products.