2.8
General Information
GENERAL REFERENCE
Standard Bolt Torque Specification
Fuel / Oil Premix Ratios
Formula:
• 1 Gallon = 128 Ounces
• 128 ÷ (Desired Ratio) = Ounces of oil for every 1 gallon
of fuel.
• 128 ÷ 20 (20:1 Ratio) = 6.4 ounces of oil for every 1
gallon of fuel.
Always mix ratio in 5 gallon increments.
Gasoline Volatility
When gasoline is blended, it is given a Reid Vapor Pressure
(RVP) number which reflects its ability to vaporize or mix with
air at a given temperature range. Gasoline vapor pressure is
measured by putting a sample of fuel inside a closed container
and applying a specified amount of heat to the container for a
certain amount of time. RVP will vary from about 7.0 PSI during
the summer to approximately 13.5 PSI during the colder
months. Service stations selling a large volume of fuel will
normally have the correct blend to work well at all times
throughout the year in their local area.
When the weather is very cold, gasoline must be able to vaporize
very quickly in order for an engine to start and warm up
properly. If summer blend fuel is being used in the winter, little
or no vaporization will occur. Droplets will form causing
flooding and very hard starting.
If winter blend fuel is being used during the summer months, it
may cause vapor lock (boiling fuel) inside the fuel lines, fuel
pump, or carburetor. This will cause warm engine drive ability
problems and hard starting when warm.
BOLT SIZE
THREADS/IN
GRADE 2
FT-LB(N-M)
GRADE 5
FT-LB(N-M)
GRADE 8
FT-LB(N-M)
1/4 20 5 (7) 8 (11) 12 (16)
1/4 28 6 (8) 10 (14) 14 (19)
5/16 18 11 (15) 17 (23) 25 (35)
5/16 24 12 (16) 19 (26) 29 (40)
3/8 16 20 (27) 30 (40) 45 (62)
3/8 24 23 (32) 35 (48) 50 (69)
7/16 14 30 (40) 50 (69) 70 (97)
7/16 20 35 (48) 55 (76) 80 (110)
1/2 13 50 (69) 75 (104) 110 (152)
1/2 20 55 (76) 90 (124) 120 (166)
FT-LB X 1.356 = N-M
N-M X.7376 = FT-LB
FUEL
(GALLONS)
20:1 RATIO
(OUNCES OF OIL)
32:1 RATIO
(OUNCES OF OIL)
16.44
53220
10 64 40
Grade 2
Grade 5
Grade 8
MAXIMUM REID VAPOR
AMBIENT AIR TEMP
R
ANGE
CLASS PRESSURE LOW HIGH
A 7.0 psi (0.5 bar)
60°F
(16°C)
110°F+
(43°C+)
B 9.0 psi (0.6 bar)
50°F
(10°C)
110°F
(43°C)
C 10.5psi (0.7 bar)
40°F
(4°C)
97°F (36°C)
D 12.0psi (0.8 bar)
30°F
(-1°C)
85°F (29°C)
E 13.5psi (0.9 bar)
20°F
(-7°C)
69°F (21°C)
Add 2.45°F for each 1000 ft (305m) above sea level
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