Hey everyone, new to karting here and im trying to get a general sense of what gearing I should be aiming for at my local tracks. Specifically, I’ll be running Buttonwillow, Sonoma, Dixon, Little 99, and Prairie City. This all came about because I made the mistake of ordering an O-Ring chain (110L) thinking I’d be able to use a chain breaker and adjust as needed but that’s obviously not the case. I’m not competing, I’m not trying to set local track records, but I do want to go out with a good baseline setup with regards to sprocket and chain length combinations and fine tune from there without spending several hundreds on chains/sprockets that won’t work.
I know apex for KA senior is 10/77ish.
In my experience most tracks are between 10/73-10/80 for a KA.
You can always call a regional engine builder and they’ll give you a more accurate range for a track specifically. Even for track day fun havers, having 5-6 rear sprockets and a spare engine sprocket (in the case of the ka mounted on the clutch bell) ready to go at the track is helpful.
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With that big long chain, I’d be tempted to buy 11t and 12t drivers and two 87t sprockets. 12/87 will be more efficient than 10/73.
I also recommemd not using an aluminum sprocket. I like the Extron Pro sprockets.
An 87 tooth sprocket (Kevlar nonetheless) will last all of three corners before it bottoms out on a curb or stray pebble and explodes into dust. Highly do not recommend.
Before buying hundreds of dollars worth of drive sprockets and enormous rear sprockets that you’ll never use after you buy the correct size chain, I would just spend the $30 on a new chain in the proper length…
Eric is pretty spot on with the gearing range. I find 10/72 to be about the lowest I ever go and 10/82 to be about the highest across a variety of tracks.
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10/87 is the TaG gear at East Lansing, and I’ve made 11/87 survive at Adams. I made a 11/89 last for a single race on a Rotax at East Lansing before my 10t drivers came in.
Time to slap on the elusive 9t drive sprocket 
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When I was bad at driving as a kid, I ran some high 80-tooth gears at Dousman, but had to pick the spots I was going to drop a wheel carefully. Turn 1 was basically a death sentence if you hooked the outside curb with a 87+ gear.
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Ran the 9T for one race this year, you have to take it off and grease it with heavy red after every session. And even then, the bushing crumbles a bit more every time. My brother’s seized at a race start and threw a clutch shoe over the T1 fence. Do not recommend.