Main air jet / Pilot air jet and other questions....

Ok so i read somewhere that the main air jet and pilot air jet are backwards in the manual.

I need someone to help lift this fog from my eyes.

Which one of these is the Main air jet?

A or B?

how do you tell?

I'm pretty sure the last time i had my carbs off and was looking them over that i don't have the washers that go under the main jet and the pilot jet in all the carbs.... is this bad?

also I have a 1983 xj750 is 4 into 1 exhaust factory?

 

The "easy" way to remember it is that the main AIR jet goes directly above the main FUEL jet......so, the main air jet goes in the "center" hole.

The pilot AIR jet goes directly above the pilot FUEL jet, and since the pilot fuel jet is more "forward" in the carb body (forward towards the cylinder head), then the pilot air jet goes in the most-forward location.

The "rear" location is for an air jet cover plate hold-down screw, which is not used in all Hitachi carbs.


The air jets are "opposite" in relative side to the fuel jets...........so since the main fuel jet is larger in size than the pilot fuel jet, it's reversed for the air jets (pilot air jet is huge in size/number compared to the main air jet).


In the picture above, the caption is reversed, but a careful viewing of the picture shows the large (pilot air) jet in the proper ocation, as well as the small (main air) jet in it's proper location.

 

ok cool....

but is 4 into 1 exhaust factory or was it 2 into one's with the collector?

also the no sealing / spacer washer under the main jet and pilot jet in the fuel bowl? bad?

 

I can never remember either so I spray carb cleaner down them. The main air jet will spray the carburetor cleaner into that hole you pulled the emulsion tube from. The pilot air jet will spray out the hole you pulled the pilot screw from.

Chacal is correct that the smaller air jet is the main and the larger is the pilot. This is counter-intuitive unless you have a deep understanding of how the pilot circuit works.

For clarity, in your picture (which I assume is from the Haynes manual, I've never seen one) A is the pilot air jet and B is the main air jet.

 

Main FUEL jet uses a copper spacer washer under it (between it and the emulsion tube); pilot FUEL jet does not use a spacer.

 

Stock exhaust was 4 into 2.

Should be a washer under the main fuel jet. I don't believe the pilot jet gets one.