Yuasa which is the manufacturer of the stock battery also makes another battery with the same layout and dimensions but with more amperage. The stock battery is part no. ytx9-bs the upgrade is a yt12a-bs. The upgrade has 175 cca compared to 120cca for the stocker. The battery is actually OE on some Suzuki street bikes and could probably be found at one of their dealers. The larger battery would definitely help out with cold weather starts and those pesky aftermarket CDI's. You can check out the specs for yourself at www.yuasabatteries.com

Clint

 

Also, get ahold of Jason at http://lrdperformance.com/. The have a battery for the 400ex that is 180 cca. it is a must for the cdi mod and cold start problem.

 

Boy, talk about perfect timing! I need to get a new battery for the 400ex today and want one with more CCA. Thanks for the info!