Adjusting The Ignition Pick-up Coil Air Gaps

[3Phase]

With Columbo in pieces all over the garage I finally found a 'tuit and made a short pictorial.


Adjusting the ignition pick-up coil air gaps

Remove the left-hand crankcase timing cover and turn the Timing Plate CLOCKWISE until the "F" mark aligns with the timing pointer.

The crankshaft is now in position to set the air gap on the #1/#4 ignition pick-up coil.




Remove the retaining bolt from the Timing Plate and put a hardened steel washer on the bolt.





Put the bolt back through the Governor Assembly.

Carefully tighten the bolt until the washer contacts the alignment lugs for the Timing Plate.

Do not overtighten the bolt, you're just trying to hold the Governor Assembly in place in the end of the crankshaft while you set the pick-up coil air gap.





Use a non-magnetic feeler gauge to set the pick-up air gap to 0.70 mm (0.0276 in).

I made a Go/No-Go gauge with a brass feeler gauge and two steel feeler gauges.
The brass goes against the pick-up coil and won't 'stick' to the magnet in the coil.

0.254 mm (0.010 in) brass
0.432 mm (0.017 in) steel
0.457 mm (0.018 in) steel

Go:
0.432 mm (0.17 in)+ 0.254 mm (0.010 in) = 0.686 mm (0.027 in)

No-Go:
0.457 mm (0.018 in) + 0.254 mm (0.010 in) = 0.711 mm (0.028 in)





Use a Phillips screwdriver to loosen both of the lock screws for the pick-up coil.





Use the "Go" gauge first to set the air gap to 0.686 mm (0.027 in).

Re-check the air gap with the 0.711 mm (0.028 in) No-Go gauge.

Tighten both of the Phillips locking screws on the pick-up coil, then check the air gap again with the Go and No-Go gauges.





Reinstall the Timing Plate and slowly turn the crankshaft CLOCKWISE until the small timing hole in the Timing Plate aligns with the timing pointer.

Remove the Timing Plate and carefully tighten the bolt to hold the Governor Assembly in place.

The #2/#3 pick-up coil can now be adjusted.

When you're finished, remove the washer from the bolt, reinstall the Timing Plate and the timing cover and go for a ride.




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[IanDMacDonald]

This is a great guide 3Phase! But, for those of us not familiar with the particulars of these air gaps, is there any sign that air gaps are off prior to messing with them?

[3Phase]

This is a great guide 3Phase!

Thank you, Ian!

But, for those of us not familiar with the particulars of these air gaps, is there any sign that air gaps are off prior to messing with them?

If the factory seal paint daubs are still on the pick-up coil locking screws -- leave the air gap alone! Change it at your own risk!

If the factory paint daubs on the pick-up coil locking screws are missing you can almost bet someone has been into the pick-up coils. Check the air gap.


Symptoms? It's similar to dwell but not exactly: hard starting; misfiring; bad gas mileage, and so on. It's got to be pretty far out of kilter to cause anything noticeable while you're riding.

Gap too big: low and late voltage from the pick-up coils to the TCI.
Gap way too big: voltage too low and too late for the TCI to fire correctly.

Gap too small: high and early voltage from the pick-up coil to the TCI.
Gap way too small: reluctor hits pick-up coil when the engine gets hot and breaks stuff. You will notice this when attempting to ride.

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[Bonz]

What the heck got you to pick this as project of the day? The only air gap I have ever heard of, on this forum, ever, is between my ears.

[3Phase]

What the heck got you to pick this as project of the day? The only air gap I have ever heard of, on this forum, ever, is between my ears.

The reason I had to set the air gaps in the first place was because one of the pick-up coils on Columbo went bad. A spare set of pick-up coils, naturally, only had one good coil too so I had to do things the hard way, R&R the coils and reset the air gaps.

Oh, and be careful using regular steel feeler gauges. If you futz with the gapping too much you can magnetize the reluctor and then it'll have to be demagnetized or replaced, whichever is least convenient.


After that I was working on the mechanical advance and it sort of snowballed from there:-
The Mechanical (centrifugal) Advance

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[natemoen]

Now in previous discussions here it has been established that the the gap doesn't matter as long as it is not greater than 0.7mm. It was even said that the smaller the gap the better.

Thoughts?

[TADracer]

I fiddled around with this a few years ago. I went as close as .3mm and widened it out to .5 mm and that is where it is still set. I am sure if one puts on gauges and timing lights and degree wheels, etc. you could measure whether that little bit makes a real difference in the timing of when the reluctor causes the coil field to collapse.

I noticed no difference in performance or plug color at all so I never went back in there to put it back to .7mm. Have not experienced any TCI or coil problems at .5 mm.

Very good tutorial, though.

[3Phase]

Thank you, Tad!

If it acts up I'll try 0.60 mm and 0.50 mm but so far (today anyway! ) it started and idled fine cold and runs great!

Nate,

I pulled everything out to grease the mechanical advance again and since there's factory TSB floating around somewhere that mentioned the 0.70 mm air gap setting that's where I set it for the demo.

The key part is the placement of the washer, not the air gap. You can, as I think BA80 mentioned, use a nut but I used a hardened exhaust manifold washer from the parts bucket. Whatever you decide to use it has to sit on the Timing Plate alignment lugs when the bolt is cinched down and not on the reluctor retaining circlip.

If anything is tightened onto the circlip it can bend or break the clip.
If the clip breaks, the reluctor moves around on the shaft and hits the back of the Timing Plate while the engine is running.
If the clip bends, it binds the reluctor so it can't advance or retard correctly.

Be careful!

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[IanDMacDonald]

Or, if you have bad luck like me, your timing plate bolt becomes loose, and shoots right through the side of your ignition cover, leading you to believe you have a bent crank when you see the timing plate wobble, when all it is, is the advance unit out of place . . .

[3Phase]

Repost: Adjusting The Ignition Pick-up Coil Air Gaps

REPOST MISSING PICTURES


With Columbo in pieces all over the garage I finally found a 'tuit and made a short pictorial.


Adjusting the ignition pick-up coil air gaps

Remove the left-hand crankcase timing cover and turn the Timing Plate CLOCKWISE until the "F" mark aligns with the timing pointer.

The crankshaft is now in position to set the air gap on the #1/#4 ignition pick-up coil.



Remove the retaining bolt from the Timing Plate and put a hardened steel washer on the bolt.



Put the bolt back through the Governor Assembly.

Carefully tighten the bolt until the washer contacts the alignment lugs for the Timing Plate.

Do not overtighten the bolt, you're just trying to hold the Governor Assembly in place in the end of the crankshaft while you set the pick-up coil air gap.




Use a non-magnetic feeler gauge to set the pick-up air gap to 0.70 mm (0.0276 in).

I made a Go/No-Go gauge with a brass feeler gauge and two steel feeler gauges.
The brass goes against the pick-up coil and won't 'stick' to the magnet in the coil.

0.254 mm (0.010 in) brass
0.432 mm (0.017 in) steel
0.457 mm (0.018 in) steel

Go:
0.432 mm (0.17 in)+ 0.254 mm (0.010 in) = 0.686 mm (0.027 in)

No-Go:
0.457 mm (0.018 in) + 0.254 mm (0.010 in) = 0.711 mm (0.028 in)



Use a Phillips screwdriver to loosen both of the lock screws for the pick-up coil.



Use the "Go" gauge first to set the air gap to 0.686 mm (0.027 in).

Re-check the air gap with the 0.711 mm (0.028 in) No-Go gauge.

Tighten both of the Phillips locking screws on the pick-up coil, then check the air gap again with the Go and No-Go gauges.




Reinstall the Timing Plate and slowly turn the crankshaft CLOCKWISE until the small timing hole in the Timing Plate aligns with the timing pointer.

Remove the Timing Plate and carefully tighten the bolt to hold the Governor Assembly in place.

The #2/#3 pick-up coil can now be adjusted.

When you're finished, remove the washer from the bolt, reinstall the Timing Plate and the timing cover and go for a ride.

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