– 3 –
3. Motor pulley and belt
Sewing speed of
the machine
(sti/min)
50Hz
60Hz
Pulley size
(mm)
Belt size
(inch)
Pulley size
(mm)
Belt size
(inch)
4,500
ø 100
M-39
ø 85
M-38
4,800
ø 110
M-40
ø 90
M-38
5,000
ø 115
M-40
ø 95
M-39
5,500
ø 125
M-41
ø 105
M-39
5,800
ø 135
M-42
ø 110
M-40
6,000
ø 140
M-42
ø 115
M-40
6,200
ø 145
M-43
ø 120
M-41
6,500
ø 150
M-43
ø 125
M-41
MF-7900 Series
Sewing speed of
the machine
(sti/min)
50Hz
60Hz
Pulley size
(mm)
Belt size
(inch)
Pulley size
(mm)
Belt size
(inch)
3,500
ø 80
M-38
ø 65
M-37
4,000
ø 90
M-38
ø 75
M-37
4,500
ø 100
M-39
ø 85
M-38
4,800
ø 110
M-40
ø 90
M-38
5,000
ø 115
M-40
ø 95
M-39
MF-7900D Series
1. The table shows the numbers when a 3-phase 2-pole 400 W clutch motor (1/2 HP) is used.
2. The commercially-available motor pulley near to the counted value is designated since the outside diam-
eter of the commercially-available motor pulley counts by 5 mm.
3. When you use a new sewing machine, use the following sewing speed for the first 200 hours (approxi-
mately one month). A good result can be obtained in terms of the durability.
• MF-7900 Series : 4,500 sti/min or less
• MF-7900D Series : 4,000 sti/min or less
(Caution) 1. Use a motor pulley which is adaptable to this sewing machine.
2. This sewing machine will exceed its max. revolutions and max. sewing speed, finally
leading to the occurrence of malfunction, unless the adaptable motor pulley is used.
