Jet size chart versus actual hole diameter??

[Dirtcrasher]

Is there a chart that states what the actual hole diameter is based on the jets size. For example, a 144 main jet equals .032 etc etc.

I ask because years ago when I called Sudco and spoke to someone he claimed that the best way to jet a carb when more fuel was desired was to simply drill it out until you are satisfied with the jetting. I had a 0-60 index case and did as he suggested and it worked out great. I have since jetted everything this way and had no problems, although you cannot go back down. My only concern was that a drilled hole may not be a smooth as a purchased jet and could upset the mixture. He told me not to worry but if I was overly concerned that I should get it close and then buy the jet new with the same diameter hole I created with a drill bit.

So, now I have a bag of jets that I have tinkered with and would like to know roughly what there equivalent to a jet size is in comparison to the actual hole I drilled. Has anyone seen a chart such as this? I'd like to print one out for the shop...... Thanks for any help.

[Billy Golightly]

I have not ever seen anything like that for the Keihin carbs, but if someone would be willing to start making one I'd help out with it however I could.

[3WW Star-Yamahondaman]

we have gauge pins at work ... i'll "pin" all of my KEIHIN Jets rangeing from 135-210 .. and post them or PM them to you .. also
sometimes we use a Tip Cleaner for a Torch to dial some things in because drills normally drill .0005-.002 Oversize ..

[Dirtcrasher]

Ahhh yes, you know what I'm talkin bout. A drill bit never drills a true hole, just a reamer or boring bar. I'm close in sizing with a bit but it's certainly not as accurate as a gauge pin.

There has to be a chart somewhere......

Thanks guys

[Yamada]

In the september 07 issue of dirt wheel mag, in the dialed in article there is a chart. the guys was having trouble jetting his banshee ( mikuni carb?????) and the author of the article give a chart for jet #200 to 237.5.
Decimal/#/Drill jet
0.0787/ /200
0.0810/ 46 /206
0.0820/ 45 /208
0.0827/ /210
0.0860/ 44 /218
0.0866/ /220
0.0890/ 43 /226
0.0906/ /230
0.0935/ 42 /237.5
Hope this help.

[4cylinders]

hey, sudco or k&l have that with the jets in the catalog.

[bobr]

I think most jets are flow tested and diameter has only a part in the overall flow.
but there must be some baseline. Bob

[200xman]

I think most jets are flow tested and diameter has only a part in the overall flow.
but there must be some baseline. Bob

You are right to a point but as long as you are using the correct style jet for the carb, enlarging the hole is an easy and cheap option.