Which gear ratio?

[morepoweranything]

I have a 16 horse briggs twin cylinder opposed horizontal engine on my go kart with a 48 driven on the axle and a 10 drive on the clutch and the engine does not even struggle a bit to reach speed I was wondering what other ratio I should use for more speed I was thinking about a 4 to 1 ratio what you guys think?

 

[OzFab]

As you probably know by now, there are many variables involved in calculating a drive gear ratio: tyre size, kart weight, driver weight, etc. However, increasing the drive ratio will not affect the engine but, it may, potentially, destroy your clutch...

All I can say is, if you're willing to sacrifice your clutch to find out, give it a try...

Another way to increase top speed is to adjust or remove the governor, therefore, increasing the engine's max RPM

 

[morepoweranything]

The clutch I bought is an extra heavy duty noram enforcer the one that is supposed to be good to up to 40 horses I bought it from heeters I paid like 250 for the darn thing!

 

[OzFab]

That matters not; in exaggerated terms, it's the immovable object (the kart) vs the unstoppable force (the engine); directly linked, no one knows which would win but, as soon as you put a link inbetween them (in this case, the clutch), the link will be the weak point & is sure to break first...

What I'm trying to say is, no matter how good or expensive the clutch is, it will still burn out if you gearing is too high...

 

[KartFab]

Fabroman is right on the money here. Think of it this way. Have you ever driven a stick shift/manual car? If you lets say, try to start it in first gear and let out the clutch, its no big deal you move on, but then you change the gear ratio this time by trying to start it in 4th gear. If you tried to move from stop in 3rd or 4th gear every time (even though i think you could 'possibly' get it going from 3rd or 4th) you would wear out your clutch really fast.

Just to add something else. Have you tried a torque converter? I bought a kart from a guy that had a souped up 16 hp briggs on it that went 100 mph (the kart was in bad shape, i suspect he crashed it and saved the motor)

Anyway, my point is this. He had a 40 series torque converter on it. I looked at the kart pretty closely and noticed that he had a 16 tooth jackshaft sprocket to a 54 tooth axle sprocket with massive tires....

So my actual point is this. The weak point in this system was the jackshaft sprocket, not the clutch (your centrifugal clutch is the weak point, why not make it the jackshaft sprocket?)

I noticed that the key had almost sheared off of the jackshaft sprocket because of the insane amount of torque the engine was putting off to the jackshaft sprocket/resistance from that stupid gear ratio of 3.375/1 WITH big tires.