weak spark, what to check? UPDATE, problem identified

[elwood440]

Email sent. What's the worst that can happen right?

[desertrefugee]

UPDATE: I got no real leads here for what I can check, so I went to a friend of a friend who has a bike speed shop with a dyno to do troubleshooting.

I'm sorry for piping up, but I could not pass on it. With two pages of folks working with you on this - and quite a few observations that were spot on with respect to the final problem, I'm not seeing how you came up with this notion. You tested the coils for continuity back a while - but with an ignition problem you described, they'll always be suspect. There's a big difference between weak and intermittent.

[elwood440]

I'm sorry for piping up, but I could not pass on it. With two pages of folks working with you on this - and quite a few observations that were spot on with respect to the final problem, I'm not seeing how you came up with this notion. You tested the coils for continuity back a while - but with an ignition problem you described, they'll always be suspect. There's a big difference between weak and intermittent.

I apologize. Your last post did indeed have some good suggestions. However, most of the rest was me clarifying my compression numbers because I put down a very wrong number, and then a lot of info about "spark shaping" theory, and then some of me explaining what I did with my HT leads. Nowhere (until your well thought out post) did anyone suggest something along the lines of "make sure that X measures Y" or "take this off and try again" or "try running it like this" or "use this tool to see what the strength of your spark is." I guess that is what I was looking for, because none of the testing I could come up with was pointing to anything.

So thank you for your suggestions. I did do a static test of the primary voltage, BTW. It's about 1.5v lower than battery, which I know is not ideal, but it's all due to the old wires. All of the connections and switches have been cleaned and the ones I've tested have zero or close to zero drop across the connector or switch. I could try to introduce a relay if 1.5 is too much of a drop.

But that still wouldn't have identified the bad coil. I could only test the resistance, and that was good. I was hoping to find a way to figure that out before springing for a new pair, in case they were not the problem.

Again, I am sorry to have offended you.

[desertrefugee]

I really wasn't offended personally - but disappointed that the team here didn't get more credit than that. Lots of honest suggestions (not just mine) were provided based on symptoms described, a couple of which were incorrect. I had thought some solid leads were definitely provided. We're all just out to keep everyone running!

But, now that you mention the dyno analysis, how did a dyno run diagnose two of four cylinders being at fault? Were you monitoring each cylinder? Most dyno runs simply watch RPM, measure torque and calculate HP. What did those guys do differently? I'm just trying to find out how an intermittent coil was conclusively identified. Not saying that's not it, but how it was concluded.

[elwood440]

The operator could tell there was a misfire by how it felt and sounded (the same things I was feeling, but he is much more attuned to it) and it was showing very lean, which backed up the misfire theory because the misfires would be sending a lot more oxygen straight thru. After that he moved the rpm pickup wire (just like the clip on a timing light) between the coil wires. The readout has a simulated RPM gauge that would give a steady reading when clipped to either of the front cylinder wires, and the needle would jump around randomly when clipped to either of the rear cylinder plug wires. This convinced him that a coil is at fault, and makes total sense to me.

I'm sure there are other ways to troubleshoot, but this guy runs his dyno often and sees some of everything come thru his shop. It really gives a good indication of a lot of things going on in the engine, not just HP numbers. Plus it can show you just what's happening while running under load and at different speeds. Something you can't do sitting static in the garage.

[elwood440]

After some communication between Dynatek and myself, they gave me an RMA and I sent the Dyna-S plate to them for testing. They confirmed that the plate was at fault and offered a replacement at a significant discount. VERY generous of them, seeing as they were able to identify that it was OVER 24 YEARS OLD! I will take them up on the offer and report back when it is re-installed.

[Whiskerfish]

Yea they have a history of being good like that.