The opposite side of the air jet...

[Johnny K]

First of all, what is that called? And never really paid any attention when I took my carbs off realized that they varied in size. My 4th carb looks like a tiny drill went through it. I took some pics and labled. Not the sharpest, but hope you can see the difference.

Carb #1:


Carb #2:


Carb #3:


Carb #4:

[psyguy]

thats your main air-jet
on my carbs they are not replaceable (just a hole in the main body cast really)
but your pics suggest that you may be able to take them out
surely theyd all have to be the same size

[Johnny K]

That's exactly mine too. I know the air jets and have taken them out. Im talking about the ones directly across from air jets. Those I cannot take out. Just wondered why the different sizes of the holes. Thanks psyguy.

[psyguy]

the air jets that you CAN take out are PILOT air-jets (have a slot in them)
opposit side are the MAIN air jets
mine are just part of the cast, the same zinc-alu colour as the rest of the carb body (not just a hole though, still have a spec size)
yours seem like a brass inserts

[Johnny K]

Oh okay, sorry about that. Yeah they are brass inserts. Would that be the part of the dyno-jet stage III set-up? But yeah, they vary and my 4th carb is drilled into. Just wondering if there was a link just so that I can read about the main air jets so that I can get a better understanding of why they do not have slots to tighten or loosen them.

[Killer2600]

Oh okay, sorry about that. Yeah they are brass inserts. Would that be the part of the dyno-jet stage III set-up? But yeah, they vary and my 4th carb is drilled into. Just wondering if there was a link just so that I can read about the main air jets so that I can get a better understanding of why they do not have slots to tighten or loosen them.

They aren't intended to be replaced/serviced and are thus just pressed in.

[Johnny K]

I found a link to the dyno jet site. They talked about drilling that brass part and measuring this and tuning that.... way past my knowledge but very intriguing. That explains why my 4th carb looks exactly like it was drilled. My question is: How do I know that those "specs" on the main air jets are right for my carbs? Basically trust in my mechanic? Is that what people talk about when they say "jetting" or "re jet"? They have to use the drill on the main air jet? I pose many questions and ask for patience.

[chef1366]

That is a Dynojet press in main air jet. It makes it smaller and changes the air mixture at the main jet. Basically it richens it up.

[Johnny K]

So in order to re-jet, you have to drill/screw that main jet and re-install a new one and drill that to spec if you want to re-jet??

[chef1366]

Those are there to stay. You should have Dynojet main jets installed in the carbs.

They all are supposed to be the same size though.

[psyguy]

the stock main air jet (non-usa models) is referred to as 1.7
i think that might be a hole diameter measurement in milimeters, not sure though
if yours are aftermarket press-in system air-jets you should be able to take that last one (#4) out and replace it with a size similar to the others

i would also THINK that when re-jetting for performance intake/exhaust (and/or a big-bore kit) you would go UP on the stock size on both the fuel and the air jets - as the air jet works in conjuction with the fuel jet - a bigger flow of air is going to pick up (pull) more fuel through the (larger) fuel jet

[Johnny K]

None are then same size chef, its weird. But I dont know enough to try to explain or understand the whole drilling process and why its different sizes. I guess when I have time I will go and stop by my mechanic early this week and just ask I guess. Come to think of it, the screw/locknut for synching is different slightly in lengths. If I compare the 3 springs, they vary in tiny amounts from each carb. I dunno, the whole process is way over my head and am just trying to understand each concept.