Very weak spark

[MarkT]

George - red blown bobber below - has a very weak spark.  Could see it only on #2 & 4.  Not on the others. Very hard to start even with a new fully charged battery and jumped to a car.  Replaced the plugs, gapped correctly with new at .031".  Now I can see a very weak spark on all 6 while using my strong readers in the shade.  Very hard to start before installing the Dyna3000.  Once it's started - by persisting for perhaps a half hour, and adjusting the choke in minute amounts, and the idle speed.  Eventually it'll pop and I'll keep at it for awhile, it'll pop a few times and die.  After many times of that, it will finally run long enough to warm up some and keep running.  Once it's been warmed up, it starts easy the rest of the day with no choke.

I have never seen a running engine have a spark this weak.  Even a lawnmower with magneto and weak spark, has more spark than this.

It did this with the original ICM and the D3000. - Hard to start that is.

BTW the plugs read a bit cold, perhaps a bit rich, but they aren't reading out of range - seriously off. Fuel is fresh premium.  Blower is an early Magnacharger.  Don't recall the carb model or know it's jetting but it runs well when warmed up.  And with the newly installed D3000 the hesitation at mid ranges this bike always had - even back in 2001 when George still had it, I rode it then - is gone using curve 6.

Also the valves are set correctly.  I know tight valves can make a bike hard to start.  First thing I looked at when I got the bike.

Diagnosing this weak spark - comments?  Have you fixed a weak spark?

[Ricky-D]

I think most ignitions that are controlled by an ECM, and work by grounding the coil rather than by energizing the coil so there is no way you can verify the coils are getting the full count of energy they desire.

I'd suggest to insure the ECM is fully grounded and also getting the full amount of energy the battery is capable of producing.

***

[MarkT]

Took the plugs removed from George and plugged into Jade to see what the Valkyrie spark is supposed to look like.  Good hot spark on all 6.  I have seen hotter sparks on car ignitions but Jade starts instantly and runs with no miss so I have a good visual of what it should look like, and verified these plugs are OK.

I'll stick the D3000 on Jade and observe the results.  Also could stick Jades ICM on George and do the same.  That won't address if there's a bad connection elsewhere but should tell me on the ICM status.

Don't want the D3000 to be the problem as it's unobtainable except by luck and spendy if you find one and it fixed the hesitation problem.

[WintrSol]

Forced induction generally requires a much hotter spark, as the pressure literally blows the spark out. For testing, do you have access to an oscilloscope? If so, you can check both hot and signal side of a coil to see if the Voltages are what they should  be. Since it is all 6, it is something common to all 3 coils, so ground to the ignition, or high resistance in the power source (run/stop switch?). Or, steady exposure to the higher pressures has caused the coils to begin arcing internally; unlikely, but swapping coils would easily eliminate this option.

[Bagger John - #3785]

Did the condition suddenly develop?

Something else to check is the output of the ignition pulsers. I seem to recall this being a problem way back when with replacement ignition trigger wheels. (Specifically, the Air-Lake version vs. the ones offered by HDL.) The latter required a bit of fiddling with the pulsers to get a strong spark signal.

A similar condition might be present with George.

[MarkT]

Not the D3000.  Works fine on Jade.  And restoring the OEM ICM on George shows same weak spark.  Glad the D3000 not to blame.  Since all sparks weak - unlikely the coils unless they all developed same problem. Can see more spark on 2 & 4 - but they are powered by different coils.  Not the induction blowing out the spark - the spark is weak visually outside the engine. There is an issue with the kill sw - and I see it's directly in the coil circuit.  Need to clean it out anyway.  It's next.  While a jumper past the sw will prove if that's the culprit.  Bl/Lg to Bl/W.  Or shortcut, 12v to Bl/W checks the whole power side.

When all else fails RYFM. The schematic indicates it's a pretty simple circuit.  At least outside the black box ICM.

(When I was TS on Olivetti boxes for AT&T, folks who called in for free support, and the answer is in their manual, we called Riffems.  We started charging phone sex rates for support - $3/minute - and then they started Reading their F'n Manual.)

I would have guessed the ignition pulsars operated in a binary fashion - either worked or not.  And since there's some spark, figured that worked. But I'll look into that if the power to the coils Bl/W and the ICM ground is OK.  Also the trigger wheel is reported to be OEM but I haven't opened the front and looked at it myself.

[WintrSol]

Moving the ignition proves it is OK, but not the ground it gets from the harness, but may have improved the ground when returned. High resistance in the power to the coils would be my guess. Bypassing the switches, both the one on the grip and the key switch would be my next step, too. Odds are, it's the switch on the grip.

[MarkT]

Yep that was my guess too.  Jumpered 12v to the Bl/W wire, power directly to coils.  No help.  What's left is the ground off the ICM (or possibly bad conn on one of the connectors).  I guess this means - if this checks out and I'm better than 50% that will be it - got bit by a bad ground AGAIN.

Breakin for lunch - was hoping good spark on the last test and lunch was reward (since I quit smokin 27 years ago). Now it's not a reward just lunchtime.

[MarkT]

Put a quality meter on the green wire at pin 14 ICM.  No impedence on Jade or George.  Not much left.  Signal generator and possibly some pin connections say at the ICM plug. The coils themselves but I don't give that much probability as all 3 would have to be failing. Guess it's back to RYFM.  Or if I get some tips here.  Have a look at the signal gen, see if there's some testing possible there.

Checking the manual, there are tests I can run with a peak voltage adapter.  YEA I have one of those, looks like it wasn't a useless purchase after all.  Only been say 5 years since I used it once.  So with a fresh day tomorrow will step through their voltage tests.

[turtle254]

Put a quality meter on the green wire at pin 14 ICM.  No impedence on Jade or George.  Not much left.  Signal generator and possibly some pin connections say at the ICM plug. The coils themselves but I don't give that much probability as all 3 would have to be failing. Guess it's back to RYFM.  Or if I get some tips here.  Have a look at the signal gen, see if there's some testing possible there.

Checking the manual, there are tests I can run with a peak voltage adapter.  YEA I have one of those, looks like it wasn't a useless purchase after all.  Only been say 5 years since I used it once.  So with a fresh day tomorrow will step through their voltage tests.

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