Jet sizes - Comparable across different carbs?

[youngjohn]

Are main & pilot jets calibrated the same across different carb manufacturers?
So in other words, will a Keihin 100 main jet and 40 pilot have the same size holes in them as a Dellorto 100 main and 40 pilot?

[Tractorman]

Yes, the hole sizes are an engineering measurement so will be the same size what ever jet it is. Of course thread size and jet shape will vary.

[Knowledge]

This is not true across all carb manufacturers.

For example, Dell'Orto measure the diameter of the hole (40 = 0.4mm diameter hole), while Amal are flow-rated, where the hole-size is indicative of how much fuel it can flow in a pre-described time.

In many ways, the flow-rated system is more informative, as a Dell'orto jet increasing from 160 to 165 will flow comparatively much more fuel than a jet that increases from 50 to 55. Do the maths for the cross-sectional areas, and then calculate the percentage increase for each jet.

By compasionShow your calculations in the margin, and stand by for more homework next week.

[Storkfoot]

Mikuni and Keihin are flow, Dell'orto are not.

[Dimitrios_231]

This is the Mikuni list.

Jet Size CC/Min Jet bore
10 0.273
15 0.335
20 0.387
25 0.432
30 0.474
35 0.511
40 0.547
45 0.580
50 0.611
55 0.641
60 0.670
65 0.697
70 0.723
75 0.749
80 0.773
85 0.797
90 0.820
95 0.843
100 0.865
105 0.886
110 0.907
115 0.927
120 0.947
130 0.986
140 1.023
150 1.059
160 1.094
170 1.127
180 1.160
190 1.192
200 1.223
210 1.253
220 1.282
230 1.311
240 1.339
250 1.367
260 1.394
270 1.421
280 1.447
290 1.472
300 1.498
310 1.522
320 1.547
330 1.571
340 1.594
350 1.617
360 1.640
370 1.663
380 1.685
390 1.707
400 1.729
410 1.751
420 1.772
430 1.793
440 1.814
450 1.834
460 1.854
470 1.874
480 1.894
490 1.914
500 1.933
510 1.953
520 1.972
530 1.990
540 2.009
550 2.028
560 2.046
570 2.064
580 2.082
590 2.100
600 2.118
610 2.135
620 2.153
630 2.170
640 2.187
650 2.204
660 2.221
670 2.238
680 2.255
690 2.271
700 2.287
710 2.304
720 2.320
730 2.336
740 2.352
750 2.368
760 2.384
770 2.399
780 2.415
790 2.430
800 2.445
820 2.476
840 2.506
860 2.535
880 2.565
900 2.594
950 2.665
1000 2.734
1050 2.802
1100 2.868
1150 2.932
1200 2.995
1250 3.057
1300 3.117
1350 3.177
1400 3.235
1500 3.349
1600 3.458
1700 3.565
1800 3.668
1900 3.769
2000 3.867
2100 3.962
2200 4.055
2300 4.146
2400 4.236
2500 4.323

[Tractorman]

This is not true across all carb manufacturers.

For example, Dell'Orto measure the diameter of the hole (40 = 0.4mm diameter hole), while Amal are flow-rated, where the hole-size is indicative of how much fuel it can flow in a pre-described time.

In many ways, the flow-rated system is more informative, as a Dell'orto jet increasing from 160 to 165 will flow comparatively much more fuel than a jet that increases from 50 to 55. Do the maths for the cross-sectional areas, and then calculate the percentage increase for each jet.

By compasionShow your calculations in the margin, and stand by for more homework next week.

I stand correct by your Knowledge