Carb Question

[Toolmaker Tim]

How many holes should be in the emulsion jets? I have 2 different versions with different numbers of holes. How many holes should the emulsion jets for a 79SF have?

[bikerphil]

The SF has 2 different emulsion tubes, ones with less holes in carbs 2 and 3, ones with more holes in carbs 1 and 4. The ones with less holes have a richer mixture to keep the inner cylinders running cooler. Normal on an SF.

[dbeardslee]

The outer emulsion tubes should be labeled 266 X2, and the inners should be labeled 301 X2. I was just working on SF carbs this afternoon and had to verify the same thing.

[Toolmaker Tim]

Emulsion Tubes

Well that explains a couple of things. Right now I have 266x2 in all the carbs, which means that cylinders 2&3 are running lean. That explains the popping and the headers glowing like they did a couple of times. Back to the carb bowls! Thank you!

[dbeardslee]

The F models have 266 X2's across the board, and they use the same needles as the SF. Mine are all the same, and I've got a Jardine 4/1, but I've never seen it glowing red. Then again, I've never really looked at them in the dark to see if there's a glow - I'm usually about 2 feet behind them . Ivan says the Jardine spaghetti pipes will glow sometimes, so maybe it's just a Jardine thing. What do your plugs look like?

[Toolmaker Tim]

Glowing Headers

Right now my plugs look unused cause of rear brake problems to go with the rest of it! I got my Viton tipped needle valves in and they work great. Plastic floats are in, no binding. Rebuilt a XS rear M/C, didn't work, wouldn't bleed out the air, leaked everywhere. Put my XJ master on and it bled out just fine, but the ************* brake stop light switch spring broke The bike is fighting me every step of the way it seems.

[latexeses]

Question...

Didn't the different jetting on the inboard carbs start with the 80G models??

[dbeardslee]

It's not the jetting that's different - just the emulsion tubes. For some reason the SF has 5 degrees less mechanical advance on it to. Don't know why.

[bikerphil]

Question...

Didn\'t the different jetting on the inboard carbs start with the 80G models??

Yes, the main jet size was increased on the middle 2 carbs in 1980. I think on the 79SF, they tried the richer emulsion tubes first, but it didn\'t make the cut, so in 1980 they went with larger mains to get \'er done.

[latexeses]

I'll have to check notes but I think when I pulled my carbs down every number from every piece I took out and cleaned matched with every carb.

Now you have me wondering.

[skids]

I have been into 81H and 80SG carbs and found 110 mains all the way across. I am sure that no one was into the carbs before. The emulsion tubes were different for the middle carbs on at least one of those sets. I think the air bleeds for the middle carbs had fewer holes = richer, cooler mix.

I'll have to check notes but I think when I pulled my carbs down every number from every piece I took out and cleaned matched with every carb.

Now you have me wondering.

[Toolmaker Tim]

78-79 & 80-81 Differences

It's pretty strange that the main jet size dropped from 137.5 to 110. When I first got my bike it had 105's in it. Now that I know a LITTLE something about the carbs, it seems like the bike shouldn't have run at all. The really funny part is it took me 4 bent valves before I figured out what I was doing wrong.

[dbeardslee]

The earlier model carbs only draw gas up through the main jet, and there's a plug over the pilot jet tower. In the later model carbs, the pilots draw their gas directly from the bowl, hence the smaller mains.

[Toolmaker Tim]

Ok, so the combination of the pilot jet and the smaller main add up to what the older carbs had as a seperate set of circuits.

[TomRodgers]

My 81 has the rubber caps on the pilot towers........... as do both of the 80's sets of carbs....

seems that there are many different combos used on carb sets of different years.......