What generation is your KLR?
What is the maximum voltage your regulator allows after a long run? (If, that is, you have a volt display always visible.)
Do you have lots of starts for rides of 40 minutes or less or do you often ride an hour or longer?
Have you used an AGM battery and how long has it lasted?
I know the Gen 2 regulator is different from the Gen 1 regulator but I don't know if the voltage is lower. I would really hope so. The voltage on my Gen 1 regulator is far higher than an AGM should ever endure.
I have a Deka that will fit but the Deka technical page: http://www.dekabatteries.com/assets/base/0139.pdf
says that the maximum charging voltage is lower than my typical voltage. Float voltage is even lower. (Float voltage is after the battery has been recharged and the system is simply maintaining the charge. KLRs don't have a different float voltage, but keeps the voltage high as if the battery was still discharged.)
I have a 3 bikes that use the exact same batteries. One of those bikes has become a long-term project so a Deka AGM is kind-of available. But I don't want to toast it and I'm not fond of spending on a new regulator to be kinder to the battery. Then again I hate getting the bat out for watering.
MY HYPOTHESIS is that people who successfully use AGMs have either a Gen 2 KLR or lots of starts and fewer long runs.