That issue was observed in two known cases on our 12 tooth sprockets althought was not revealed during prototype and production acceptance testing unfortunately. The root cause was determined to be inadequate press fit between the sprocket bearing and the sprocket. We issued a recall on those sprockets and supplied replacement sprockets from SMC to those impacted customers and provided detailed instructions on how to replace them.
From that point forward, we discontinued offering our own 12 tooth sprockets and now only offer Vortex Red Sprockets from SMC. We have a few customers that are in the 20-25 horsepower range running 12 tooth SMC sprockets on drag bikes with success. The SMC Vortex Red clutch and sprocket design is a proven and time tested design in the karting world which is why the design was selected in the first place.
If you have any concerns, we would encourage you to use a 15+ tooth sprocket. The larger sprockets have the advantage in that the bearing can be positioned directly in line with the sprocket, thus eliminating the moment loads on the bearing.
)
Welcome aboard Grape...you'll fit in just fine. No...not THAT much has changed in 20 years....it's just harder to see the little parts these days ...(know what I mean? Thank God for readers!)