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Anyone heard of a procedure or spec on gapping the pulse generator (PG) coils in an 84? The Clymer manual (with major errors in the electrical section) says "not adjustable" and "0.016 - 0.040" range (which is odd since its "not adjustable").

Heres the scenario. Removed engine, then Right PG (Yellow) but not the Left, removed housing, reinstalled. Left PG is now dead (the one that wasn't removed from the case). 5 Vpp AC on Left (Blue), 60 Vpp Ac on Right (Yellow) per oscilloscope. Engine started and ran on two cylinders driven from the Right PG with the other two firing occasionally (Left PG). The PG that hadn't been removed had failed.

Removed PG housing and measured/calculated stack ups and found the PG's are adjustable from interference to + 0.049" with significant rotation. Tested the PGs on a test stand and read a slight difference in voltage, but nothing like the difference when installed.

Gapped both at 0.016" and reinstalled the housing, now they are both low voltage, about 15V PP. Installed gaps are 0.016" Left and 0.020" Right which is good considering I gapped them before installation. Engine wouldnt start last night although the battery was weak and I didnt use the choke.

The PG'sread within 5% on resistance / inductance and mechanically. The Left one has a slightly weaker magnet. The PG's have a magnetic strip on front, they are in position (toward the rotor) within about 0.005" of each other.

A new set of pulse coils mightfix it, but we dont learn anything that way, not to mention that "throwing parts on" is illegal in many US States. Next step is to close the gaps incrementally and see if the pulse voltages increase and if enginestarts to run.

Two odd things:

1.) The Yellow one, which I initially removed and put back in the case with no alignment done, was at 60V, while the one I didnt touch was low. Should have been the Yellow one that misfired, but it wasnt.

2.)The replacement parts are sold already installed in the PG case which makes me think the alignment is very critical.

What gives? Where Brojees my EE mate?
 

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Just a thought Dave. If you got major differences in readings on the yellow one after refitting, would this not indicate a faluty ignition box instead?
 

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That was my first guess also, especially after an ignition fuse blew - bad ICU right? Thats what I thought...

But nothing bad turned up there but some questionable solder joints. I did learn something about the ICU, the large silver metal thing has an encapsulated computer chip inside. Very hard thing to take off the board and harder to reinstall.

But, the readings were also amisswith the ICU disconnected. So thats why I went down "PG avenue."
 

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Can you swap the PGs?Wonder if theload impedance on the twois the same? That bit about being non adjustable makes me wonder why one couldn't oval out the two mounting holes with a jeweler's file so as to be able to match them? Probably wouldn't be worth the effort since I suspect when things are operating properly there's plenty of drive pulse amplitude available.
 

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The mounting holes are already oversized for adjustment. But that only tell min/max adjustment, not what its supposed to be. I cant believe it doesnt matter, maybe its something adjusted at factory since it comes pre assembled?

They cant be swapped in the case because of how theyre moulded.

Sometimes the questions outnumber the answers...:(
 

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Hi, in the Honda Service Manual 1984 - 1987 in the ignition section it says:

"Inspection

Remove the left side cover and disconnect the pulse generator coupler.

Measure resistance: White/yellow and yellow leads (1-2 cylinders), White/blue and blue leads (3-4 cylinders).

Resistance: 1200 +/- 100Ohms at 20 C (68 F)"

"Air Gap Check

Inspect the air gap between the pulse generator rotot and pickup.

Air Gap: 0.40--0.90 mm (0.016--0.035 in)

Install the pulse generator cover.

'84: Install the swing arm (see page 12-34).

After '84: Install the timing covers."

Hope this might help.
 
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