Jet Sizes

[brianinpa]

I want to clear the fog that I have in my head, and I need some help for that.

When jet sizes are referred to as 030, 035, 040, etc., is that metric measurement or thousandth of an inch? The number stamped on my idle jet is 558 and the number stamped on my main jet is 127.5.

Now my mind tells me that the hole in the main jet should be smaller than the hole in the idle jet because 127.5 is less than 558, but that isn't the case.

If I could find one of these, that would solve some of my confusion...

 

[joedrum]

the sizes are metric i think brian the numbers on the jets on the carb could be useless numbers crap ...micro bits actually go up number for smaller hole that whole mess was and still is very confusing to me

what idiots come up with this stuff...dft carbs have no weber numbers on the emulsion tubes ...but there weber tubes and had to match pictures to make any sense of them

it sucks when things are plastered with useless numbers ...

 

[dan filipi]

.030, .035 etc is a metric measurement.

 

[Dusterdude]

Dan,i would think any number labeled as . anything is an american decimal not metric.i could be wrong tho

 

[joedrum]

you would think so duster ...but im rather sure dan is right ..my bits came from england and they were mm on the package and seem to correspond to the .035 numbers and so on

 

[Dusterdude]

Interesting

 

[brianinpa]

.035 mm = 0.001377953 inch... that is one very fine drill bit.

I am still having a hard time clearing the fog.

 

[joedrum]

clearing fog is secondary to getting the bike to run great .... :hihihi:

 

[brianinpa]

mm to inch conversion:
1 = .039
.9 = .035
.8 = .031
.7 = .027
.6 = .023
.5 = .019

My drill bits aren't any smaller than .5 mm, and I don't see me jetting anything smaller that that drill bit.

Dan, is your idle jet really drilled out to .001377953 inches?

 

[joedrum]

ok im not getting this brian ...if you look up weber carb bits on ebay or something ...they are designated .035 and so on ....they are metric .....035 is what the stock carb racks come with also ...its the same size as small string on guitar ....dans running the .035 idle jet in his solex witch is different than you guys solex ...im running the dft carb about that size also...single carb needs about the same size as stock and it isnt any harder to supply all 4 pistons from the same size ....most of the car carbs come with much bigger idle jet like .050 and i think solex is bigger .060...so ....and on the solex the idle circuit has additional jetting that adjustable to some degree ...before main ...its hard to get main dial in if idle is off to start with ....unlike others ..id say this carb should dial in nice

 

[brianinpa]

So maybe the .035 isn't millimeters but another metric measure. I just want to make sure I use the correct size drill bit when I begin to drill out the jet size. I have some more reading to do...

 

[dan filipi]

There is a misunderstanding with expressing the numbers. I had to look at the jet bit sizes I have from Weber.
0.35 mm idle is what I'm running. It is very tiny.

 

[brianinpa]

Ok. Now that makes sense. .35 is a lot bigger than .035 mm.

 

[slabghost]

might be in centimeters? I really don't know.

 

[dan filipi]

slabghost » 8 minutes ago[/url]":25m4leh7]
might be in centimeters? I really don't know.

Lol no, 10 mm is 1 centimeter.

 

[slabghost]

Shows how much I know about the metric system.

 

[joedrum]

gee look what a dot can do in the wrong place LOL :doh: :hihihi:

 

[brianinpa]

joedrum » Thu Oct 15, 2015 5:22 pm[/url]":120yd8xq]
gee look what a dot can do in the wrong place LOL :doh: :hihihi:

Exactly! That is why I was so danged confused and I wasn't drilling anything until I was sure.

 

[brianinpa]

Size 80 drill bit is 0.135 inch which is approximately 0.35 mm.

 

[joedrum]

that for sure is true brian ...ive done that many times on clearing stock racks idle jets #80 micro bit ....be careful bit will break easy ...i always do it by hand ....if bit has collar ring ..its all the handle you need