Briggs 18.5 twin specifications and hard to start when hot

In my experience the opposed twin CDIs fail considerably more often then B&S singles or V twins which use 2 coils. First you might want to install a fuel line shut off and turn the gas off a few seconds before shutting the engine off. Or you can do this by clamping the fuel line. Sometimes fuel leaks on thru float needle flooding the engine until fuel evaporates off. On some of these engines the fuel line ran thru the cooling shroud causing vapor lock sometimes. I agree that the coil mounting surfaces need to be bright clean but to ground the coil properly not for heat transfer.

Coils do fail gradually sometimes. It is common on these opposed twins for failing coils to start an engine when one plug wire is disconnected, some say when that wire is then grounded to the engine. I have not experienced that. Might try it.

Walt Conner

ILENGINE said:

I have replaced maybe half a dozen of modules on the opposed twins in the last 20 years, so they are not any more problematic than the rest of the modules briggs or other brands. They fire two plugs on each revolution of the engine, but all the induction modules fire on all small engines every revolution be it briggs, kohler or kawasaki.

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I've had to replace many more than I could ever count or remember in the 10 years I've had a repair shop, though I rarely get them in anymore. I'm on my third on my own lawn tractor. I'm serious....google Briggs Opposed Twin coil problems. I'm glad you've had good luck with them, wish I did. And btw, the 20 HP coil, although it looks a little different, will swap out with the 15 HP perfectly. I've got a 15, and the last coil I installed was for a 20 and so far it's lasted longer than the 15's.