Razor PR200 Drivetrain (Stock)
This includes the specification on the stock parts and research on
alternatives.
Motor
Stock Motor 
Model  Zhejiang Unite Motor Co. Ltd. #MY1016 
Type  Brush 
Voltage  24 Volt DC 
Output  250 Watts 
Efficiency  ≥78% 
Rated Speed  2750 RPM (3350 NoLoad) 
Rated Current  ≤13.4 Amps (≤1.6 NoLoad) 
Rated Torque  0.90 Nm 
Sprocket  #25 Chain, 11T 
Body Dia/Length  101 / 108 mm (4 / 41/4") 
Shaft Dia/Length  10 / 26.5 mm 
Mount Points  41/4" x 21/8", 4x M6x1.00 [Detail] 
Weight  2660 g (5.86 lbs) 
DC Motor Formulas 
Power  V x I x EFF 
Horse Power  (V x I x EFF)/746 
Current  P/(V x EFF) 
Efficiency  (746 x HP)/(V x I) 
 V = Voltage
 I = CURRENT (amps)
 P = POWER (watts)
 EFF = Efficieny
 HP = Horsepower
1 Watt(w) = 1 Nm/s or 0.738 Ftlbs/s or 1.341E03 hp
1 Horsepower (hp) = 746 Watts or 550 FtLbs/s
check the internal resistance of your motor by DMM(ohms)across the two input wires.
V/R = stall current (maximum current you can push through it at a particular voltage)
It looks like the 36V 350W Unite MY1016 motor is the biggest that is a straight
bolton. It's specs are nearly identical except for the 1.22 Nm of torque (136%).
Bigger motors (MY1020) should fit but, you'll have to drill new mount holes and make
a spacer (~1") because they're too long to fit between the frame rails. The bigger
motors are a better use of your money.
Motor Links
Gearing
Stock Tire:  3.004 (10"x3.5" / 260x85mm) 
Tire Circumference:  800 mm (0.0005 or 1/2000 mi) 
Stock Gearing:  11/65 (1:5.91) 
Stock Chain:  #25 Chain, 126 links 
#25 Gearing available from tncscooters.com: 1115/55,65,68,72,80
11/55  1:5.00 
12/55  1:4.58 
13/55  1:4.23 
14/55  1:3.93 
15/55  1:3.67 
11/65  1:5.91 
12/65  1:5.42 
13/65  1:5.00 
14/65  1:4.64 
15/65  1:4.33 
11/68  1:6.18 
12/68  1:5.67 
13/68  1:5.23 
14/68  1:4.86 
15/68  1:4.53 
11/72  1:6.55 
12/72  1:6.00 
13/72  1:5.54 
14/72  1:5.14 
15/72  1:4.80 
11/80  1:7.27 
12/80  1:6.67 
13/80  1:6.15 
14/80  1:5.71 
15/80  1:5.33 

MPH  Wheel RPM  Motor RPM* 
1:5.91 (11/65)  1:500 (13/65)  1:4.33 (15/65)  1:3.67 (15/55)  1:3.06 (18/55) 
10  332  1,962  1,660  1,438  1,218  1,016 
15  500  2,955  2,500  2,165  1,835  1,530 
20  667  3,942  3,335  2,888  2,448  2,041 
25  833  4,923  4,165  3,607  3,057  2,549 
30  1,000  5,910  5,000  4,333  3,670  3,060 
35  1,167  6,897  5,835  5,053  4,283  3,571 
40  1,333  7,878  6,665  5,772  4,892  4,079 
* Depends on gearing.

Running the stock 24volt, 250watt, 3000 rpm motor at 36volts got me to about 22 mph
at 4,326 motor rpm. This leads me to believe that getting to 40 MPH may be difficult.
Even with the tallest gearing available from tncscooters.com (15/55) we're looking at
4,892 rpm but, 35 mph would be a doable 4,283 rpm based on this single reference point.
Mr. Exon claims to have hit 40 mph but, forum
posts
show him and others using a 34" (864 mm) wheel circumference based on his math that a 10" tire
x pi = 34" (dπ=c) instead of 31.4". Assuming that he never caught that math error then his actual
speed was closer to 36.9 mph. Whatever his actual speed was, it does tell me that it is possible to
get 150% of the rated rpm for a motor and that the tires probably will not immediately disintegrate
at 3540 mph.
#25 Gearing Links:
Chain
The PR200 comes with a 126link ANSI #25 chain stock. Generally speaking you would
want to add/subtract links as you add/subtract teeth on your gearing but, you may be able
to compensate for a few teeth with the chain adjusters on the rear axle.
Other small electric vehicles may use a T8F chain which I've also included in the table
below for reference.
Size  Standard  Pitch  Roller diameter  Tensile strength  Working load 
25  ANSI B29.1 / ISO 606  1/4" (6.35 mm)  0.130" (3.30 mm)  781 lb (354 kg)  140 lb (64 kg) 
T8F   5/16" (8.00 mm)  0.180" (4.70 mm)  2,293 lb (10.2 kN)  
Tires
Stock Tires 
Brand 
Qing Da (Razor Branded) Street Treaded Tire 
Size  3.004 (10"x3"x4", 260x85)* 
Type  Requires Innertube 
Ply Rating (PR)  4 
PSI  45 
Load  264 Lbs under pressure 
Overall Diameter  254 mm 
Section Width  86 mm 
Certifications  ECE E4 (vs DOT) 
Tire Circumference: 800 mm
Theoretically, a 10" or 260mm tire would have a 797.6 mm or a 816.4 mm circumference
respectively. I measured the circumference at 800 mm (within, say, ± 2 mm) and
used this number when configuring my speedometer.
Tire Size*: 10x3x4 or 260x85
1st number is the outside diameter of the tire, the 2nd number is the overall
width and the third number, if used, represents the inside tire diameter, or
the outside diameter of the rim.
Speed Rating: Unknown
My initial searching suggests that your two options are the stock Qing Da tires or
Kenda's as an alternative. Neither brand lists a speed rating but internet reports
suggest that the Qing Da's can handle at least a few moments at 3540 mph.
Tire Links:
Tire Speed Ratings: A5=16mph, A8=25mph, B=31mph, D=40mph, F=50mph, J=62 mph
January 25, 2012
