You are exaclty right Mikey: the battery I got is #3. Apparently the size has changed.
Good point on the WD40. Will give it a go. Thanks!!
Hi Fransisco- I installed a Costco battery in my DIL's 99RX300 (#3) and it fit perfect. I might suggest on thing on the rear bolt though, if it does not come off fairly easy with the use of penetrating oil, you may have to remove the air cleaner box so that you have axcess to the rear bolt to hold it with pliers or vice grips. A better suggestion would be to remove both cables first and after you have removed the front bolt, turn the bracket 90 degrees and you should be able to slip the old battery out and the new in without even dealing with the rear bolt. I have done this numerous times when I was in a hurry just to save time even on one where the bolt would come out. It generally works fine. Hope that helps. Roger
Matter of fact when I stop to think of it, I think when you remove the front bolt the hold down should just pivot up and come out of the lower hole without ever loosening the rear nut.
Hi Roger, I just replaced the battery with no issues following your tip of removing the front bolt.
Thanks very much!!!
Francisco