# I wanna see a port map 50+mph

How do you get total reduction I'm sorry I haven't gotten the whole mathematics aspect of this
The engine has a 4.1:1 internal reduction. The drive sprockets for the single ratio drive on 26' wheels are 32t÷10t=3.2. Then it's 4.1×3.2=13.12:1

The ratios input to output for a Sturmey Archer fixed gear 3 speed internal geared hub are 1:3/4, 1:1, 1:4/3. Just remember when doing division to calculate reduction for the IGH the fractions have to be inverted.

The reduction are as follows
First gear reduction
4/3

Second gear reduction
1/1

Third gear reduction
3/4

The 10:20; 20:44 is the same as a 10:44

So then the basis math looks like this

First Gear Reduction
(4.1×(4÷3)×(44÷10))=24.05:1

Second Gear Reduction
(4.1×4.4)=18.04:1

Third Gear Reduction
(4.1×(3÷4)×4.4)=13.53:1

Sorry I haven't updated this I'm on a felt faker gas frame now with triple tree forks and disk break in the front and rim break in the back both set up just right trust me I can stop lol
I did not intend to be condescending in my first post. Safety is and should be the most important factor. Because...if you do a humpty dumpty flip act off the bike at 50 you will not have to worry about speed for a long, long time.

Ok then here is the path I took to upgrade my engine... As I stated in my earlier post, there's many ways to get a motorized bicycle to get to 50mph.

I have a single speed pedal bike. No gears...and a 10/38T sprockets on the engine side.

I copied almost everything from others forum members. I had one forum member help me a LOT with advice along the way.

The 50 mph barrier was not my intentions when I set out to upgrade. Just have a reliable engine which has the power to roll me along at speeds about 30-35 mph, not be over taching, and not need pedaling too much to start off.

I bought a long rod 40mm engine from CDH Power, a Mineralli vertical cylinder spacer/VM20 intake/reed/ and carb insulator from Smolik Performance, a VM20 clone on Ebay (there's many imposters so you have to be careful choosing), a capnip cdi(I paid \$29. He is now \$200 for the same thing!) an Athena cylinder kit(070100), and a Jog 50 pipe on Ebay.

Edit: forgot bearings...4 bearings rated for 13K I think..PGN

Most everything is bolt on and run except balancing the crank, fabbing a magneto key that retards the timing some, and custom fitting the Jog pipe. No stuffing, porting, or other mods.

This all cost right about \$575 for it all shipped to my door. I do realize there are cheaper or faster set ups. I bought mine a piece at a time over many months so I did not have to lay out \$575 all at one time.

This set up has been very reliable and performs beyond my expectations. It will get above 50 mph as I have done it quite as few times and it does not take holding the throttle pinned for a long stretch to get there. These's a good bit of power left in the tank when I let off. I lose my nerve going that fast on a bicycle. I have visions of a locked rear wheel or either tire blow out.

I started with a cheap chinese Mineralli kit and did not balance the crank with that kit to the extent it's now balanced & trued. A ring guide pin came out and scored the cylinder. I suspect the excessive vibes contributed to this failure...or it was just chinese junk.

I did not intend to be condescending in my first post. Safety is and should be the most important factor. Because...if you do a humpty dumpty flip act off the bike at 50 you will not have to worry about speed for a long, long time.

Ok then here is the path I took to upgrade my engine... As I stated in my earlier post, there's many ways to get a motorized bicycle to get to 50mph.

I have a single speed pedal bike. No gears...and a 10/38T sprockets on the engine side.

I copied almost everything from others forum members. I had one forum member help me a LOT with advice along the way.

The 50 mph barrier was not my intentions when I set out to upgrade. Just have a reliable engine which has the power to roll me along at speeds about 30-35 mph, not be over taching, and not need pedaling too much to start off.

I bought a long rod 40mm engine from CDH Power, a Mineralli vertical cylinder spacer/VM20 intake/reed/ and carb insulator from Smolik Performance, a VM20 clone on Ebay (there's many imposters so you have to be careful choosing), a capnip cdi(I paid \$29. He is now \$200 for the same thing!) an Athena cylinder kit(070100), and a Jog 50 pipe on Ebay.

Edit: forgot bearings...4 bearings rated for 13K I think..PGN

Most everything is bolt on and run except balancing the crank, fabbing a magneto key that retards the timing some, and custom fitting the Jog pipe. No stuffing, porting, or other mods.

This all cost right about \$575 for it all shipped to my door. I do realize there are cheaper or faster set ups. I bought mine a piece at a time over many months so I did not have to lay out \$575 all at one time.

This set up has been very reliable and performs beyond my expectations. It will get above 50 mph as I have done it quite as few times and it does not take holding the throttle pinned for a long stretch to get there. These's a good bit of power left in the tank when I let off. I lose my nerve going that fast on a bicycle. I have visions of a locked rear wheel or either tire blow out.

I started with a cheap chinese Mineralli kit and did not balance the crank with that kit to the extent it's now balanced & trued. A ring guide pin came out and scored the cylinder. I suspect the excessive vibes contributed to this failure...or it was just chinese junk.
With your setup it'd take 7050 rpm to do 35 mph and 10,072 rpm to do 50 mph.

Using this calculator… 26 inch tire height, and 15.2 as the ratio 4(38/10)=15.2

35mph = 7296 rpm’s
50mph = 9822 rpm’s

I have a cheap tach so I’m not sure if it’s very accurate but the numbers are close to those above.

Using this calculator… 26 inch tire height, and 15.2 as the ratio 4(38/10)=15.2

35mph = 7296 rpm’s
50mph = 9822 rpm’s

I have a cheap tach so I’m not sure if it’s very accurate but the numbers are close to those above.

If you're using a GPS for a speedometer that's probably what's off. Your engine's internal reduction is 4.1:1 not 4:1. Get a bicycle computer, they're much more accurate as a speedometer.

Your Total Reduction is 15.58:1 not 15.2:1

4.1×3.8=15.58

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