I have a kohler k181s. What type of coil do I need and do I need an external resistor?
Thanks for any help you can give.

You could use a Kohler magneto coil but their hard to find and cost upwards of 80$. Tecumseh coil was direct replacement except for wire length and is still very available. You can buy new one around $20 shipped. Hope this was Helpful

Hi,
If this a battery ignition unit, find the Kohler coil and do not worry about it, or an aftermarket replacement. The Kohler number is 41-519-21-S and the Oregon Number is 33-333. Huge difference in price; about $80 for the OEM and $35 for the Oregon. See the service manual at:
http://www.asberry.net/files/TP-2379.pdf
And the Oregon can be looked up at:
Passport®: OEP Power Search by OREGON®
And Oregon is at:
Kohler Ignition and Magneto Coils
Peace,
Clarke