Another coil question..

[Guy_b_g]

I sent off for the Dyna 1.5 ohm coils but received a set of 2.2 ohm coils instead. Can they be made to work on a '78 Standard, and if so...what type/value of resistor do I need?

Thanks!

[TopCatGr58]

Hey Guy,

I looked at the DynaTek website, and it looks like they sent you the DC4-1 models instead of the DC2-1 model??

One thing I couldn't find in their limited tech information is what volts the primaries are made for, 12V or 9V?

The older machines use a ballast resistor which you should already have wired into your harness that provide the additional 1.5 ohms which get added to the 1.5 ohms of the coils for a total of 3 ohms total load for the TCI. But the resistor also drops the voltage from 12 volts to around 9 volts which was to help not run the coils so hot/burn them up. They get the full 12 volts during startup because the TCI bypasses the resistor to provide a stronger spark, but once started, routes the power thru the resistor.

Their site states that their coils are made to replace OEM coils, so I would think that the 1.5 ohm style was designed to run at the lower voltage. Whereas I don't know what the 2.2 ohm coils are supposed to run at?? However, running it on your machine with the OEM resistor should not hurt the TCI since it would just put a slightly higher load/resistance, which is better than running too low resistance which draws too much thru the TCI and this is what usually burns up the TCI's, folks putting CDI type ~0.7 ohm coils on instead of the 1.5 ~3.0 ohm coils on these older TCI type bikes!

The 3 ohm coils in the later model XS11's don't use the resistor and run the full 12 volts all the time.

I guess you missed this tech tip in the Mods/Electrical section, could have saved you a fair amount of $$, and still provided a much stronger than stock spark.....IMHO! It's your $$
T.C.

[Guy_b_g]

Hey TC,

Yeah...I did see that tech article quite some time ago now that you mention it...

Totally forgot about it tho..

Saw some Dyna coils at a decent price from a vendor at ebay and snagged them up.

They were advertised as 1.5 ohm coils, but when they arrived they were 2.2 ohm. I already wrote them and asked for an exchange..they said np.. send em. I also complained to them that although the coils appear brand new...the box had fingerprints all over it and all the connectors were missing...I think someone else returned these coils also...and they tried to get rid of them again...just guessing tho...they could have made an honest mistake too, I suppose.

I was just thinking it might be worthwhile to use them, if a resistor could be found cheaply and locally that would bring them to the proper spec.

I wonder how much I will lose in ouput performance of the coils if I go with the 1.5 ohm resistors? Maybe I should just go ahead and return them....?

[Guy_b_g]

any electrical gurus out there?

[randy]

Get a 1 Ohm 10 watt resistor for each coil, wire it in series with the red/white feed for each coil.

Digi-Key sells 'em for .49 each, part number 1.0-W-10-ND.

Link

[Guy_b_g]

The resistors are ordered....do I take the stock resistor out of the circuit, or leave it alone?

BTW, thanks Randy!

[randy]

Take the stock resistor out of the circuit and plug the two remaining ends of the harness together.

[Guy_b_g]

Randy,

I tried to PM you, won't go thru.

I looked at the stock coils, and understand exactly what you meant now...so I'm good to go!

Thanks,

[TADracer]

I will be first to admit I am no electrical guy at all (still can't figure out why one blade of a plug is bigger than the other) but, I have been runing Dyna DCI-1, 3 ohm coils with Accel 8.8mm wires on my 79 special for several years with great results.

Hardest thing I had to do is make a few small angle brackets to get theim to fit up into the frame.