You don't really need to use a timed ignitor. Just put a switch on your regular ignitor (feild box) supply and energise the supply after you have started spinning the engine with your starter. After seeing a few people struggle with delay ignitors at my feild I chose the simple approach and it's worked perfectly for the last 100 starts on my 170.

Here's what I didn't like....

one more battery to charge/manage/fail when least expected ,

one more thing in my already heavy feild box,

hard to see the LEDs on a bright day so it's difficult to tell if the glow is on or not,

how much delay is the right amount...5 secs, 10secs,

when should the engine fire??,

if the engine does not start you will have to follow the procedure for restarting the ignitor...one more thing to worry about at a contest when you're on a clock.

$100 vs $1.50 to modify your existing set-up.

Colin.