According to Pablo's web page found here:
http://pantablo500.tripod.com/id41.html
A walmart ES12bs battery will work in a GS if it is mounted sideways. Anyone try this? If so, does the battery leak at all?
After my stock battery croaked, I put one of those Walmart cells in, and it's been fine for 4 years now. No issues. Cranks it over faster than the stock one/size too.
I did it a year ago and the only issue I had was extending my ground wire. No leaks.
Good note, I didn't extend my stock wiring, just clipped the electrical tape and re-wrapped it after I pulled the wires I need out and gave it all some breathing room. Easy mod.