rear sprocket swap...what can i expect?

[motorpsycho]

well my set up now is the stock 10 tooth gear on the motor, with a 41 tooth sprocket on the rear wheel. My bike takes off from a stop the same as it did with the 44 tooth, but now it has more acceleration.
It's like by raising the gear ratio, the motor comes into it's mid range power band later, and it holds it longer. It pulls better than it ever has because the engine torque is not peaking and dropping off as soon as it was with the 44 tooth.
I only took it up to 21 mph yesterday, but at 21 mph, there's still plenty of rpms left to go more.
With the 44 tooth, it felt as if the engine was wound pretty tight at 21 mph, and it would struggle to get up to 25 mph.

 

[happycheapskate]

Thats cool. I'm ordering the 36t from Bikeberry today. I will have to drill my own 9 holes though, bummer. Still it seems the cheapest option.

For those running a 20" wheel, has anyone used a track hub with a locking fixed sprocket (say 18t ?) and a BMX freewheel or 6 speed freewheel on the pedal side?

This ought to solve the problem of the rag joint and give a seriously fast gear/wheel combo.

 

[motorpsycho]

Thats cool. I'm ordering the 36t from Bikeberry today. I will have to drill my own 9 holes though, bummer. Still it seems the cheapest option.

For those running a 20" wheel, has anyone used a track hub with a locking fixed sprocket (say 18t ?) and a BMX freewheel or 6 speed freewheel on the pedal side?

This ought to solve the problem of the rag joint and give a seriously fast gear/wheel combo.

you could use your old 44 tooth sprocket as a template to drill the 9 holes on the 36 tooth sprocket.

Right now my pedal side sprockets are 36/16 which makes peddling pretty tough with 20" wheels and 4" long cranks (like starting off in 5th gear on a ten speed.) so i am going to swap out the 16 tooth sprocket and replace it with a 19 tooth, which will lower the gear ratio and make it much easier to pedal.
I don't pedal it very much, but it will be easier when i need to.

 

[happycheapskate]

Thats what I expect to do. I plan to either make a stencil with it, or clamp them together and mark them, drill tiny pilot holes, then bigger holes. I haven't seen the pre-drilled 9 hole 36t sprockets that also have the offset teeth like the original cog. All I've seen is flat "racing sprockets". I guess those are good if you can use them, because you can flip them over when they start getting "shark teeth" and extend the life of the sprocket.

 

[happycheapskate]

I got a 38tooth 5 hole offset sprocket from Bikeberry and made it 9hole and widened the center hole with sandpaper. It works well.

BBerry sells 9hole flat 36t now for 25$

I am still thinking about the track hub with BMX rim though. Has anybody done that?

I know the pedals will drop about 2" and steering angle will slacken. That would be ok.

 

[Slowbalt]

By my best guess 'I'd say 32mph. It should still have good mid range. Best thing for those 50cc engines is a pochet bike tuned pipe.

 

[Reader]

well, the problem with a shift kit is that i can not use one.
I have a single speed rear hub(because i am using a 20" schwinn stingray with 20" wheels) and i do not have the room to add a shift kit / jack shaft to my bike. i would not be able to add say a 5 speed rear hub because the rear frame is too narrow.
yes, with a 20" wheel and a 44 tooth sprocket i can still get 25-27 mph out of my bike which is pretty good if you ask me.
Considering the fact that my rear wheel is only 20" i do not have the advantage that most guys have by running a 26" wheel.
.........

A larger rear wheel is gonna give you more top end speed...it is just the same as having a smaller rear gear. The front sprocket is opposite.

 

[Jwestie15]

Currently waiting on a shift kit and my new wheelset, but I'm building 9speed shifter on 24x1.75in rims with 1.75 tires
Should have a good combo of speed and acceleration with the shift kit and the smallish tires, will report back with real world experience after my parts get here

 

[scorpion1]

I'd go with a 40, should get you 32-33 mph

 

[Street Ryderz]

A 40 t on a 24" wheel at 8500 is 40mph and could go faster depending on the tune.