I'm sure this is an old topic but what sealed battery works in a 1973 CT3? 

Thanks...

I never found one, so instead I bent the cornered ends of the battery box to accommodate a MotoBatt MBT6N6.

I bought a rusty, beat up battery box from ebay and left my original one alone.

I don't know how the battery box dimensions compare, but here's a thread on the same subject for the CT1.

Pete might chime in once he sees this thread.

  CT1 Compatible Sealed Battery? - Vintage Enduro Discussions (yamaha-enduros.com)

According to partszilla the 82 83 xt 125 takes the same battery.

www.partzilla.com/product/yamaha/6N4-A4D...217429e87e9b3875c500


www.amazon.com/Power-Battery-Compatible-...2-1983/dp/B08MWVX8CK

Gr8uncleal wrote "Pete might chime in once he sees this thread."

I've read it Alan and here's my chime.
I didn't find a sealed alternative to fit the CT3, so I have a standard lead acid battery in mine.
I think a CT1 battery box will fit in place of the original battery box which means you can then use the smaller (70mm x 47mm x 107mm) sealed battery I use in my CT1s if a sealed battery is the goal.

Ding Dong!