$63 DIY Electronic Ignition Including Coil

[pamcopete]

You may have seen my earlier post for a complete electronic ignition system for $99. Now, the same system can be built for $63 by using a Mallory 6100M infrared module that is identical to the Accel unit and buying the coil from Mikes for $28. The Mallory unit ($34.16 from Amazon.com) uses an infrared beam interrupted by a rotating "shutter" in place of the points cam. This module is self contained (no external "black box"). Use a dual output coil from Mikes (#17-6803). Fabricate a replacement for the points cam from the shank of a bolt and drill a couple of holes in the lid from a jar of Gerber's Baby food for the shutter. Attach the lid from the baby food to the bolt shank with a couple of 4-40 screws, time it and go.



Parts List for Gerber – Mallory Pointless Ignition
Mallory 6100M $34.16 @ Amazon.com (FREE Shipping!)
Mikes XS Dual output coil #17-6803 $28.00
Bolt, ¾ X 2 in. ( You Already got one)
Jar Gerber’s Baby Food, small glass $0.69
Misc wire, connectors $0.49
Total $63.34

A drawing of the mandrel that fits on the advance rod after you have sawed off the threads on the points side. This is really the only part that has to be fabricated. Everything else is "off the shelf". I used a 3/4 in bolt that just happened to be on the workbench when I started the project. The 1.05 dimension is critical, as is the location of the thru hole for the roll pin, because of the final clearance of the Gerber lid under the points cover.



Here is a drawing of the relative position of the slots in the lid, mandrel and Accel Infrared sensor. The roll pin lines up with the leading edge of the slots and the lid mounting screws. Check this alignment with the engine timing mark set in the firing zone before drilling the offset hole in the lid, then fine tune with a strobe with the engine running.

[pamcopete]

The ballast resistor is not required for coils with a 2.5 Ohm or greater primary resistance and Mallory has just introduces their 6100M module ($34, FREE shipping from Amazon.com)that is identical to the Accel 2005 module. These changes result in a lower cost of parts.

[pamcopete]

Additional notes:

To begin with.. ..this mod requires that you remove the spark plug clearance "bulge" in both the points housing and the points housing cover in order to provide room for the module. You also have to hack saw off the threads on the points end of the advance rod.. .....and..... you have to drill out the hole for the locating pin on the points side of the advance rod to accommodate the roll pin for the mandrel... ..I think that about four people just left the room...oh well...progress has it's price!!

Drill and tap two holes to mount the Accel or Mallory module on the points plate as shown. Only one points plate advance locking screw is retained...the one on the upper left of the plate. It is absolutely essential that the metal heat sink on the bottom of the module make perfect, flat contact with the points plate!! Use heat sink "grease" between the module and the points plate. Remove the small tab that is part of the label under the module....don't know why they put it there.

The slots on the Gerber Lid are started with two 1/8 th in. holes exactly 180 deg apart. Using a rat tail file, these holes are then filed in a clockwise direction to create slots that are 90 deg "long". This will result in a 50% duty cycle of on time vs off time. Clean out the plastic coating that is inside the lid and spray paint it absolutely flat black to reduce the possibility of the infrared light bouncing around and causing false triggering.

Initial timing is established by positioning the crank on the "F" timing mark and rotating the lid on the center screw hole counter clockwise so that the leading edge of one of the slots is just at the edge of the infrared "eye" of the module. (see diagram above). Mark and drill the offset hole at this point. This establishes "initial timing" The engine should start with this initial timing. Or, If you follow the diagram and line up the roll pin with the slot as shown, that will also establish the initial timing.

Using a timing light, loosen the screw holding the points plate and rotate the plate and module to obtain proper timing at 1,200 RPM over the "F" mark, just as you would with points.

If you shine the timing light on the Gerber lid, you can see if both leading edges, as viewed on the top, of the two slots are exactly 180 deg apart. If not, then use the rat tail file to "adjust" the slot that is more advanced than the other. It's one of those things that you have to see to fully understand. This "rat tail file" timing adjustment only has to be done once. If you screw it up, then open another jar of prunes and start over.

After doing the "rat tail file" timing adjustment, redo the basic timing by rotating the points plate as before.

The Mallory or Accel comes with wiring instructions. Brown wire to ground.....Red wire to +12 from the kill switch and green wire to the coil. The other terminal on the coil goes to +12 from the ign switch.

You must use suppressor type spark plug wires and resistor spark plugs . You will have to use 5/8ths resistor plugs for clearance. I have a post of recommended plugs, but I found the best cost / performance plug to be the Bosh FR8DCX (7557).

Here is a list of reccomended spark plugs:

xs650temp.proboards29.com/index.cgi?board=ID&action=display&thread=1163124662&page=1#1163124662

The output voltage from the coil will depend on which coil you choose. Some of the "flame thrower" coils advertise up to 80,000 volts!! Wow.. ..just for our little XS650? The choice is up to you, as long as the coil has a primary resistance of at least 2.5 ohms, you can use any dual output coil that you want.

Hopefully, these notes will give you a better insight as to how to get this mod going.

[pamcopete]

Here is a PIC of the system with the lid removed:

[pamcopete]

Here is a pic of the HD OEM 31609-80 (after market 17131) coil mounted in that little corner at the front where the frame comes together.

[shifty]

hmmm seems 'almost' simple enuff. I'd want a spare advance rod and I think I have a handle on some extra parts near by .. cheap. Would bring tears to hack the threads off my original rod.

I don't understand the 1/8" holes in the cover. I do understand that they have to be exactly 180 apart. I thought they would be 'square' ... but you slot them (to adjust) with a rat tail (round) file. Does the infrared sensor fire the plugs from the leading edge of the rounded hole? Is that why the mandrel has to be exact length of 1.050"? Or, is the small difference of being 'off a bit' from 'dead center' of the leading edge rounded hole ... insignificant?

Or .... am I waaaay off in left field? Just trying to understand it.

[pamcopete]

shifty

Yes, the Mallory module fires the coil on the leading edge of the slot. The non slotted sections of the lid represent the Dwell angle, and I have set mine to 90 deg each. The exact length of the mandrel is to provide exact alignment for the slots in the lid and the infrared sensor / source on the module and to provide clearance between the lid and the "points" cover, which in my case is only about .02 in. The 1/8 in holes are on the rim of the lid and provide a starting point for the rat tail file. You are correct, a square edge would be better as the timing can change slightly with round holes as the advance rod moves very slightly in and out. I actually put a thin shim washer on the advance weights side to limit this movement.

If you do not want to saw off the threads on your advance rod (yeah, I cringed when I did it) then, of course, just drill the center hole all the way through and secure the lid with two off center screws. The problem with that is, ensuring that the lid is absolutely centered on the mandrel. But, if you have the patience, then by all means. You could go through a few lids until you get it right. (who's gonna eat all those prunes?)

[shifty]

Thanks ... that is clear, but now ...

hmmm ... I never did understand nor care what dwell angle was, until now. Reading the following: www.moyermarine.com/faq/4.5.html :

Dwell angle is a measure of the duration of time that the primary circuit of the ignition system is closed to energize the primary windings of the coil. It expressed (and measured) in degrees of rotation of the distributor rotor, hence the use of the term "angle". In actual operation, as the distributor mechanism rotates, the points (or electronic module in electronic ignition systems) are closed for a certain number of degrees of rotation, and open between these points. Simply as a matter of interest, this means that the total number of degrees during which the points are closed, plus the total number of degrees that they are open, will equal 360 degrees.

So my question is ... if the dwell angle is 90 degrees (no slot opening) ... the slot opening must also be 90 degrees (both multiply by 2) to equal 360 degrees?

Does the length of the slot matter? Seems to, in, I'm sure, my above misguided logic!

[pamcopete]

shifty
Right again! Each slot is 90 deg, so each non slotted area is also 90 deg. This means that the coil is on for 50% of the time. There is a trade off in on time on vs life of the coil due to heat build up. A 50% duty cycle (90 deg dwell) is a good compromise. A longer dwell is important for RPM's at or above 7,000 RPM because the actual time on would be longer, so if you were racing for instance, you would set the dwell angle to, like 100 deg and benefit from a hotter spark at high RPM's but a shorter coil life. In other words, although the dwell angle is constant, the time that the coil is on between "sparks" is less as the engine speed increases, so the coil has less time to fully charge before discharging, resulting in a weaker spark. Fully electronic systems control the dwell angle based on engine speed...slower speed, less dwell angle, higher speeds, more dwell angle. The Mallory module is not that sophisticated, nor does it have to be for this application.

With this system, you could actually have different lids with different dwell angles for different circumstances. Just two screws to change the lid.

[shifty]

I like to learn something each day ... mission accomplished ... thanks pcpete. Great stuff.

[pops]

I see Gerber just recalled their rice and oatmeal. I hope none of you used any lids from these bad batches. ;D

pops

[mashermoto]

Pops, I'm using the prunes...it slides on easier ;D

[pamcopete]

Well, the 650 IS a "Rice Burner"! ;D

[pamcopete]

For those of you who do not have little kids or grandkids to eat the "Gerber" prunes, you can use the lid from a small jar of "Green Giant" mushrooms.



The mushrooms are great on steak!

(Love that "REJECT IF BUTTON MOVES WHEN PRESSED")

[shifty]

Pete ... I remember telling you last fall I couldn't find Gerbers in Canada ... today I was in Shoppers Drug Mart and they carry Gerbers brand ... I did buy a bottle of prunes since you advise it helps exhaust-wise ... but I didn't thank you publicly for sending a lid my way (along with the other stuff) ... so thanks! I haven't done anything with it yet ... waiting for spring.