If the battery drops below 10.7 volts it won't even start.
I bought my wife a brand new 92 500 EFI SKS and she put 5,00o miles on it. The guy I sold it to is still riding and it has 8,000 no. That was the first year for the 500efi anf it was hard starting. They came out with an electronic fuel enrichner you could throw a switch to engage but that still did not cure the problem. I bought an electric start kit for a standard 500 (cause they didn't offer it for that EFI) and put it on the sled.
I have a friend that has a 93 sks and she has 6,000 on it she had trouble keeping the battery up. There was a wiring change on those cause the battery would drain if you used the kill switch and not the key. I have another friend with a 94 that has 4,ooo miles. If the sled will sit for any length of time disconnect the battery. Even with every thing switched off the computer draws a small amount of current.
If the brain box goes it is big bucks.