how do you go about getting in the over 50 mph club.

[CrazyDan]

With a zeda motorsports poor boy motor, mz65 pipe, 32t sprocket, and 27.5in wheels my build shouldn't have any issue hitting 50-51 if you have enough road. So far I've only gone up to 44 mph but the motor was only turning 66-6800 rpm and was still pulling. On a 44t sprocket it's good for 36mph at 85-8600 rpm, 51 or so should be doable with enough room. Not all that bad for a stock intake and stock NT carb with the stock jet.

Wait till you get your jetting dialed in.

 

[extremeodd]

Wait till you get your jetting dialed in.

Just biding my time until I get my hands on a vm18, the NT works surprisingly well at the moment and I'd rather not spend any money on jets for it.

The current plan is swap the 32t for a 36t to bring my top speed back to the "actually usable" range (from 51 to 45 @ 8.2-8.5k RPM), then get a VM18, then eventually a windowed piston + reed. Only then I'll consider swapping the 32t back on, currently the motor is strong enough for 51ish on 32t but not strong enough for it not to be a hindrance when riding in traffic (or rather next to in the bike lane).

 

[CrazyDan]

I'm done riding in the bike lane, too much debris and tired of people turning right in front of me.

 

[Street Ryderz]

With a zeda motorsports poor boy motor, mz65 pipe, 32t sprocket, and 27.5in wheels my build shouldn't have any issue hitting 50-51 if you have enough road. So far I've only gone up to 44 mph but the motor was only turning 66-6800 rpm and was still pulling. On a 44t sprocket it's good for 36mph at 85-8600 rpm, 51 or so should be doable with enough room. Not all that bad for a stock intake and stock NT carb with the stock jet.

With 10/32 gearing and a 27.5" wheel 44 mph is 7200 rpm,and a 44 tooth at 85-8600 is 39 mph not 36, With a Mz 65 pipe and 44 t gear 50 is atained at just over 11k and with a 32 t gear it would be at 8 k if the engine can pull the gearing.

 

[Sumsloppymeet]

streets right tags my setup almost to the T with 32t, mz65, vm18,ozreed and about 165lbs i hit 55 at like 9-10k rpm speeds like that i treat it like a moped ive out ran a few actually i swear im riding a feather sometimes

 

[extremeodd]

With 10/32 gearing and a 27.5" wheel 44 mph is 7200 rpm,and a 44 tooth at 85-8600 is 39 mph not 36, With a Mz 65 pipe and 44 t gear 50 is atained at just over 11k and with a 32 t gear it would be at 8 k if the engine can pull the gearing.

Maybe my digital tach is reading wrong? Not sure what to tell you, 85-8600 rpm was 36 mph for the last month.

 

[CrazyDan]

Maybe my digital tach is reading wrong? Not sure what to tell you, 85-8600 rpm was 36 mph for the last month.

What are you using for a speedometer? That might have been inaccurate. I prefer using a gear ratio calculator, like jpilot's from this forum to mathematically know what my speed will be at specific rpms. Once you learn what speed you'll be at for every 500 rpm or so you won't really need a speedo to know your speed. Then after you grow accustomed to the sound your engine makes at certain rpms you won't even need to look at your tach to know roughly how fast you are going. Changing gear ratios will throw you off for a bit when you get to that point lol.

 

[extremeodd]

I utilize various GPS spedometer apps, currently using one called Speedometer GPS as it keeps handy tabs on distance and top speed. It's reading the same as speedview did, same as DigiHUD does. Just went for a ride and was getting about 3400 RPM for 20mph and about 5300 RPM for 30-32 mph. This aligns perfectly with the calculations I'm using for engine rpm vs wheel size vs rear sprocket vs drive sprocket. I don't see how my math that I posted earlier could possibly be as wrong as is stated. If someone in the Phoenix valley area wants to lend me a good helmet and a good riding jacket I'll see exactly what RPM the engine is turning at 50mph but extrapolating from the data I've gathered, that is a pointless endeavor other than to say "I went 50 on a cheap walmart bicycle"

As for how I'm doing my math, I'm taking engine RPM divided by 4.15 (the approx reduction from crank to output gear) and plugging in the other known variables into here and the theoretical numbers are aligning perfectly with real world observations. I will correct my prior statement of 44 mph at 6400 rpm, it was 40 mph at that rpm.
http://www.diygokarts.com/speed-calculator.html

EDIT: jpilot's is showing me the exact same results.

 

[CrazyDan]

I utilize various GPS spedometer apps, currently using one called Speedometer GPS as it keeps handy tabs on distance and top speed. It's reading the same as speedview did, same as DigiHUD does. Just went for a ride and was getting about 3400 RPM for 20mph and about 5300 RPM for 30-32 mph. This aligns perfectly with the calculations I'm using for engine rpm vs wheel size vs rear sprocket vs drive sprocket. I don't see how my math that I posted earlier could possibly be as wrong as is stated. If someone in the Phoenix valley area wants to lend me a good helmet and a good riding jacket I'll see exactly what RPM the engine is turning at 50mph but extrapolating from the data I've gathered, that is a pointless endeavor other than to say "I went 50 on a cheap walmart bicycle"

As for how I'm doing my math, I'm taking engine RPM divided by 4.15 (the approx reduction from crank to output gear) and plugging in the other known variables into here and the theoretical numbers are aligning perfectly with real world observations. I will correct my prior statement of 44 mph at 6400 rpm, it was 40 mph at that rpm.
http://www.diygokarts.com/speed-calculator.html

EDIT: jpilot's is showing me the exact same results.

What are all the teeth count from the first driver sprocket/pulley to the one on the rear wheel? Also, not all wheels are alike, you need to measure your individual wheel/tire combo to know your exact size. Using different sized tires and rim width affects overall tire height as well.
Edit: doing the math and assuming your 27.5" wheel really is 27.5", 8400 rpm should be 38.094 mph with your 18.04:1 reduction, you've gotta include the 4.1:1 internal reduction on your motor (20t to 82t). Then you multiply that by the 10t output to your 44t wheel sprocket (4.4:1 reduction). Not sure where you got the 4.15 from...

 

[extremeodd]

The drive is 10 tooth, and the current rear is 32t. The math is spot on for this setup, can't tell you why with the old 44t sprocket I was always running 85-8600 rpm at 36 mph, the math is saying it should have been 38. But with the current 10/32 setup, every combo of rpm to speed that the calculators show, I'm getting in real life.