The output shaft on most (
possibly all?) of these 2:1 ratio Honda wet clutch's are 22mm. diameter...
7/8" is close to 22mm. but slightly smaller...
So I'd suggest you start by
accurately remeasuring the output shaft using a caliper tool.
Then to help confirm things, you also need to measure the width of the keyway in your output shaft with a micrometer. I've got a feeling you'll discover its exactly 7mm. wide.
Then if I'm right, here's a link to some drive sprockets that'll fit your engine:
https://www.bmikarts.com/428-Sprocket-with-22mm-Bore-7mm-Key-12T-18T_p_30602.html
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But before you order a drive sprocket, we need to figure out the best gear ratio for your situation:
1- Measure & post how many inches tall your rear tires are when they're fully inflated.
2- Get an exact tooth count on your axle sprocket.
3- Tell us what type of terrain you plan to ride your kart on?
(like will you be doing a lot of low-speed/stop & go driving in a small area, or riding the kart off road through deep mud and/or constantly climbing steep hills? ~ Or will you be pretty much only be riding at top speeds on large flat hard surfaces like paved roads or parking lots?) This is a very important aspect in selecting your gear ratio, because you can gear the kart for good acceleration & good hill climbing ability; but that'll result in lower top speeds. Or you can gear the kart for higher top speeds, but that'll result in less acceleration and hill climbing ability...
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Then we'll be able to determine the best gear ratio for you, but it'll be a little trickier than usual because we'll be compensating for the 2:1 gear ratio wet clutch on your engine.