Bonneville America Forums Forums Technical Forums General Tech Ignition Sensor a/k/a Pick Up Coil

Yes, another suspected failure...went for a ride yesterday evening...less than 10 miles later, I was on the highway marveling at how well the bike was running...RIGHT AFTER that thought, it went to crap...like someone flicked a switch...no power, no acceleration, rough as anything, banging/spitting/afterfiring...I figured as long as it would get me home on the back roads, go for it...it stalled a couple of times but immediately restarted...

Usual suspects?

CDI (Igniter) - Mine is a TTP-modded unit...doubtful.
Coils - Mine are PVL (Nology) - doubtful.
Plugs - NGK IX, as good as they come - very doubtful.
Plug wires - Magnecor (TPUSA) race wires - very doubtful.
Switches & Fuses - all in good shape, - doubtful.
Battery - New this year, just came off a tender - very doubtful.
Ignition sensor a/k/a pick up coil - OEM, never been checked, HIGHLY SUSPECT.

I started the bike from stone-cold today, & it fired right up & ran normally...hmmm...I'm thinking ignition sensor.

I have spares of all of the above on-hand, except for one part - care to guess which one?

Happened to my 06. Run. Quit. Wait. Run. Quit... P/U coil. Bet that's the one you no have.

I finally got a chance to install the new ignition sensor last night. I took the bike for a 70 mile ride this evening and it ran awesome. Looks like that was the issue.

Thanks to Dean at Hermy's for sourcing the part.

Two interesting observations...the OEM sensor grommet had no sealer whatsoever; I used some black silicone...the OEM gap was nearly 1.2mm; I gapped the new unit at .8mm

Runs great again.

Some of the fellows have had the pickup coil fail only when hot. There was a post some time ago where the fellow put his ohmmeter on the coil then dropped it into a pot full of water then heated it. The coil went open somewhere near boiling confirming the failed coil.

Glad you have the problem sorted!

Well, here's an interesting observation: with the only changes being a new ignition sensor & a narrower gap (actual may be in the .7mm -.8mm range), my bike popped like crazy on decel. I saw it on the AFM & heard it.

My theory: a narrower pick-up coil air gap has the net effect of less ignition advance. I don't know what else would explain that.

If I had it to do over again, I would gap it at 1 mm. Not going in now just for that, though.

Any other alternate explanations? Not an exhaust air or intake vacuum leak, so let's put those aside.

I really don't see how that would effect the advance as it is stationary and only sends the fire signal to the CDI then the CDI does the advance and retard end of things. I could be mistaken and maybe the smaller gap sends the signal slightly sooner than the wider gap, I don't know.

Well now...in an effort to find an explanation for the decel popping I went over every connection in the exhaust from the heads to the silencers, & here's what I found:

- port side header nuts were tight
- starboard side header nuts weren't loose, but were not as snug as they should have been
- crossover clamp was loose
- silencer clamps were tight & sealed with hi-temp copper Permatex

The proof will be in the riding, however I think I found the source of the exhaust air leak at the crossover connection that caused the excessive decel popping.

My theory is that all the detonation going on in the right pipe from the ignition sensor failure either caused or hastened the loosening of the crossover clamp & maybe even the starboard side header nuts.

I'll test it out tomorrow, weather & time permitting.

Still popping more than I prefer at low revs on decel.

Did I miss it, Ken? What's the year of your bike?

I don't know if this in any way helps, but I just started to have massive de cel popping, it started a week ago. after checking over all the rubber bits and suspecting everything else. Yesterday morning when I started it up the sound was not right. Running my hand around the headers found the problem. What looked like a small crack in the upper header. it was very hard to see. In fact it would have been under the small heat shield at the top of the head (which is no longer there)
I pulled it off and there was a small hole and a thin but long crack winding more than half way around the casting near to the header flanges.
it is out for welding today. I expect this will be the end of the popping.