Emulsion/Main jet

[egsols]

I am somewhat confused (but no more than normal)

Which are the "real" main jets the manual refers to?

I have taken out both the main and pilots, which I believe are the air jets. The main has the 140 stamped on it which agrees with the manual stating the main air jet to be a 140. BTW I am talking about the '79 carbs.

I have also taken out the emulsion tube which I had assumed was the main jet and it is marked 226. The smaller emulsion tube, hidden under the blanking plug, is what I believe to be the pilot jet, has no number on it that I can see.

Am I correct in the above?

Soooooo, what is changed during rejetting? the emulsion tubes (the hollow cylindrical thingies with holes in the sides) or the "air" jets (the round thingies with a single hole in the middle)?

One last thing, I believe my manual calls for 137.5 mains. Where is this number to be found or is the 140 my main?

[Wildkat]

This MIGHT help...

at any rate... if nothing else... someone will see that I posted and come running to correct me...


A couple of pics here that might help

Bear with me as it's been a few months since I had a set apart...
The main jets are the larger of the brass screws that you see once you take off the float bowls... with the number stamped on the end...
The pilots are located in the smaller tube next to it... IIRC, the number is stamped just below the threads... you will need good eyesight, a magnifying glass... or a child, to see it...
If you check out D.P. Laramee's post a little further down... TC posted a pic that shows 2 different mains... and a pilot or two... That might help you with the identification process...

Most of the time, I believe, when referring to rejetting... it's the mains...


Okay guys... my eyes are closed.. fire when ready, Griddly

Good luck, Ernie
There are quite a few threads regarding the carbs... a lot to weed through... but some really good info there too...

[DiverRay]

WildKat,
As usual, your close but no cigar. The '79 carbs have just a main jet and a screw plug when you remove the float bowl.
The Main jet holds the emulsion tube in the carb body, and feeds fuel to the pilot jet as well as the emulsion tube on the '79.
The main AIR JET is in the bellows area of the carb, on the air filter side. It is a SMALL jet screwed into the air intake side of the carb.
IIRC, the '79 came with the 137.5, and the 140 is the next size up. If your bike has an aftermarket exhaust system with the stock airbox, that would be the correct jet.

[Wildkat]

Well... in my defense...

(and maybe not even a good one) I was thinking 80SG carbs...
but I was right about one thing... you came to help...

[DiverRay]

I knew that, that is why I stated for the '79 carbs, as that is what I run.

[egsols]

Thanks Kat,



Diver,

The main air jet is the one screwed into the air box side of the carb? I have one there that is marked 180? The main jet resembles the air jet but screws in underneath the emulsion tube and is marked 140?

I am running a Jardine 4 into 1 (stock air box) so if the main is a 140 rather than a 137.5 it would make sense, correct?

From the above, if I change to an aftermarket 4 into 2, will the 140 be too much?

[DiverRay]

Yes, you are correct, and no, you probably do not have to change the jetting. If the plugs are looking good, light tan to dark tan, don't worry about it, just RIDE.

[egsols]

Thanks Diver...

Yeah, the plugs look good right now. If anything I might be a tad lean.

[DiverRay]

IF you adjust the float height just a little, you may be able to take care of that. .5mm lower is all you need to do. Say from 25mm to 24.5mm.

[egsols]

I have them at stock, 25.7 right now.

I need to recheck my floats though. Had issues earlier with fuel in airbox and crankcase. Carbs are totally clean and vents unrestricted.

Last time I had them apart I check and adjusted all float heights to 25.7 mm and check for closing by blowing air into fuel lines.

I think I need to pull floats and do a bouancy and leak test.

[SFerinTEXAS]

Out of curiosity egsols, Did you notice if the two inside emulsion tubes had more holes in the sides than the outside tubes ? 16 vs 10 as I recall.

[egsols]

Hey Sferin,

No I didn't even think about it at the time. I know the 79's are supposed to have no.s 2 and 3 different from 1 and 4 but all I recall is the 226 stamped on them. Next time I pull them apart, which will be soon (to recheck floats) I'll check it out.