Yeah I'd stick to the standard battery. I purchased a brand new 90 or 91 trx300 carb on eBay. The only mod I had to use was a trx300 throttle cable. My bike runs like a champ with no jetting or internal mods. I have great low end torque and more top end. I want to say I paid about $80 for the carb and about $10 for a gently used cable. Super easy bolt on. Welcome to the club!
79 110
83 185S
84 250R
3x85 Big Reds
85 200X
85 ATC 70
85 Tri-Zinger
86 200x
86 TRX 125
87 TRX 250
89 TRX 300
98 TRX 450S
03 TRX 350
5 Foreman 500 4x4's
You can never have enough! ATC250ES is still the best!