Required & recomended OMS for 12 volt coils.

gtsun

Joined
Sep 21, 2009
Messages
1,609
A few years ago I put a Pazon sure fire in my BSA Shooting Star. The paperwork with it said to make sure the 12 V coil was between 3 and 4.5 ohms. The stock one on my bike was closer to five so I thought I would buy a coil from Pazon just to make sure I had one that would work the best with their unit. So I ordered one and when I got here it tested out at 6 OMS. I just left the stock one in my bike and I have been using it all this time but recently have had some symptoms that are common to coil failure like the bike starting and idling fine but after ridding about 5 miles it starts not wanting to idle when it's hot. Since I still have this unused Pazon coil (truely a Emgo with a Pazon sticker on it) I thought I would switch them out to see if that was the problem. But since it tests out at 6 ohms I was wondering if that itself will be a problem or just not optimal? Does anyone know if this really matters that much?
 
Generally speaking, a 12 V coil of the type that was originally for points/coil ignition will do.

They are usually around 3-4 ohm.

Avoid CDI coils. They have less than 1 ohm resistance.

You can get a lot of inaccuracy, trying to measure such low resistances. Also- measured resistance may not be the same as impedance in service. Treat your readings as comparitive rather than absolute.

The higher resistance of your 6 ohm coil shouldn't harm the Pazon, although it's your risk not mine. I'd look out for a weaker spark than you get from a 3.5 ohm coil.
 
Triton Thrasher said:
Generally speaking, a 12 V coil of the type that was originally for points/coil ignition will do.

They are usually around 3-4 ohm.

Avoid CDI coils. They have less than 1 ohm resistance.

You can get a lot of inaccuracy, trying to measure such low resistances. Also- measured resistance may not be the same as impedance in service. Treat your readings as comparitive rather than absolute.

The higher resistance of your 6 ohm coil shouldn't harm the Pazon, although it's your risk not mine. I'd look out for a weaker spark than you get from a 3.5 ohm coil.
Click to expand...
 
Thank you for that information, and actually are weaker Frank is what I was afraid of and did not want. I might look through my supplies and see if I have another coil somewhere with the lower Oms.
 
Triton Thrasher said:
Generally speaking, a 12 V coil of the type that was originally for points/coil ignition will do.

They are usually around 3-4 ohm.

Avoid CDI coils. They have less than 1 ohm resistance.

You can get a lot of inaccuracy, trying to measure such low resistances. Also- measured resistance may not be the same as impedance in service. Treat your readings as comparitive rather than absolute.

The higher resistance of your 6 ohm coil shouldn't harm the Pazon, although it's your risk not mine. I'd look out for a weaker spark than you get from a 3.5 ohm coil.
Click to expand...

A 12volt coil with 3 to 5 ohms of primary resistance is what ELs like for singles. I put a PVL 4.5 ohm 12 volt coil in my Victor equipped with a Boyer MicroDigital ignition, works great. Above 5 ohms and your spark may be week, above 6 and you may not get a spark. Conversely below 3 and the current draw inside the "box" increases and decreases unit life, below 2 and you'll be lucky to get down the road very far at all. Most modern ELs like suppressor caps, I recommend 5K ohm NGK caps, check the manufacturers instruction sheet for exact details.
 
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