Denco Porting Specs

(Complete)

Denco Porting Specifications-all measurements in millimeters

 


Horsepower

Exhaust
ht. to top X port width

Boost
ht. to top X port width

Transfer
ht. to top

Intake
ht. to top X port width

Piston Skirt
Amount to Remove

H2

74 (Stock)

36.8 X 43.0

51.7

51.7

66.1 X 48.5

Stock

H2

Ultra Stock

36.8 X 43.0

51.7

51.7

95.9

6.0

H2

100

33.6 X 65% of bore

50.9 X 20.0

Stock

Stock

4.0

H2

120

32.6 X 65% of bore

49.3 X 23.0

50.9

Stock

5.22

H2

120 (King Cobra)

32.6 X 48.0

49.9 X 23.0

50.9

Stock

5.22

H2

130 (Production Road Race)

32.2 X 49.0

49.9 X 24.0

50.9

Stock

5.22

H2

141

31.5 X 49.0

49.6 X 24.0

50.9

Stock

6.1

H2

149

31.0 X 48.0

49.6 X 25.0

49.6/51.7

97.9 X Stock

4.8

 

H1

60 (Stock)

35.4 X 39.0

48.8

48.8

65.4 X 41.0

Stock

H1

70

33.8 X Stock

Stock

Stock

Stock

2.0

H1

75 (Road Race)

33.4 X Stock

Stock

Stock

Stock

1.8

H1

80

32.0 X 70%

47.0

47.9

Stock

2.25

H1

90

31.5 X 70%

47.0

47.9

Stock

2.25

 

S3 42 (Stock) 33.0 X 36 44.0 44.0 55.5 X 36.0 Stock

S3

62

29.5 X Stock

Stock

Stock

Stock

2.1

S3

66 (Road Race)

28.3 X 38.75

42.1

42.8

Stock

3.6

S3

72

28.0 X 38.75

42.1

43.0

Stock

3.8

 

S2 45 (Stock) 31.0 X 35.5 33.5 33.5 59.0 X 36.0 Stock

S2

60

28.3 X 65%

42.1

42.8

Stock

5.4

-     All intake and exhaust cut 70mm radius.

-     100HP and above must have heads milled about 0.020 and work your way up 0.010 at a time to attain 155 psi.  This is required to compensate for raising exhaust port.

-     Run only 120-130 psi for road racing.

-     All Denco heads are of the dual squish design.

-     Outside air temp where you are riding can have an effect.  Where it is cold you can get by with higher compression.  If it is hot you want to keep compression low.  You may want to have two sets of heads.

-     Higher HP versions used larger carbs, ie, 149HP version used 38mm carbs.