If I have a gearing question. If I replace a 16t clutch bell with a 20t clutch bell and keep the stock spur gear (say 46t) will I have higher top speed or lower top speed?

Wow, that a big gear change,
You'll have more top if, but your bottom will be saging
the lower the # of teeth on the bell the more torque the more teeth the higher the top speed

Thanks for the info. It is a big gear change. I'm trying to install a Fantom FR18 motor into my Terra crusher, but the Terra Crusher stock clutch bell doesn't fit onto the Fantom. I have all T-Maxx parts on the Fantom, but the clutch bell has 20t compared to 16t which is stock for the TC. I'll purchase a 16t clutch bell that is compatible with the Fantom.

so more teeth on clutch bell = faster, but less torque

Does this mean that more teeth on the spur= slower, but more torque?

yep, you got it

watch out i would only jump that mnay T if i had a .21 i dont know if a .18 can take that much