What is the best number of teeth for your rear wheel sprocket?

Depends on what your looking to get out of your bike. What kind of terrain are you in? The smaller sprocket is for more top end (less tourqe) and the larger is for more tourque.
I've found that a 36T is a good median size.

There is no one right answer to this question. Most of the 4-stroke frame mount kits come with a 56t sprocket. Where most of the 2-stroke kits come with a 44t sprocket. The reason for the difference has to do with the amount of reduction built into the motor (2-stroke) or added to the motor (4-stroke). The most popular 4-stroke motor is the HS clone of a Honda GXH50. These motors are pretty unique in the world of 4-stroke motors in that they idle at 2000rpm and have a max rpm of 7600-7800rpm. To get the total amount of reduction necessary they come with some type of primary reduction gearbox, chain drive, or belt drive that is mounted to the output side of the motor. These various primary reduction drives vary in the amount of reduction offered, from 3:1 - 5:1 . The amount of reduction in your primary affects the amount of reduction you need in your final drive.

ocscully

Hi zazbeam,

EZM's Q-Matic drive requires a 56 or larger rear sprocket when used with the 49 CC 4-stroke HS 142 or the Honda GXH50 motor. Several of the 4-stroke kits use the 56 tooth rear spocket. Several lighter riders [myself included] have used 48 tooth rear sprockets on the 4-stroke motors for testing top end limits, however the wind & hills can slow it down quickly.

There are a lot of choices in drive systems, some are really bad, some you can live with, and some that work well. As a Vendor it isn't wise to point out additional information, I just think a little research on this site might lead you down a safe path.

The 49 CC 4-stroke motor is a great choice, both Honda & H S. All H S motors are not the same, some are wider, the crankshaft length varies [important to consider because of drive choices], and crankshaft O.D. sizes vary.

Have fun,

Howdy Zaz, welcome. Read a bunch is the best advice I may offer. They all make the rear wheel spin. What ever you decide on, will be a great joy. I do feel obligated to warn ya though, It is like potato chips, can't build just one. LOL

Post lots of pics of your builds!