What year is it? The 84 200ES uses a bit of an oddball battery, its taller than the ones i was able to find in wal-mart, i was about to make a spacer to put in the bottom of the battery box to use a shorter battery and still have it held down by the battery clamp but then i found a local farm and fleet (aka runnings) store had the correct battery as it was also used in a few other pieces of lawn equipment.
Beware if you buy one of these batteries off ebay, some of them sell the battery without the acid pack and you have to go get battery acid somewhere locally. Auto parts stores can usually sell you a bottle or even fill a battery you brought in dry but its just an added expense. Also make sure you have a slow charger to put in that initial charge, i like to use an automatic charger/maintainer for powersports/lawn care equipment. It can even be left on the battery all the time to maintain it. A low slow charge the first time along with correct filling will give you a long lasting battery.
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....