Starved for fuel, emulsion tubes?

[gmac]

History: 83 Vision, 5700 miles, bought her new in '85 off the showroom floor.

Drove her for a few years, got married, had kids (you know the story) and she got neglected.

Pulled her out 4 years ago, fixed the tank, cleaned the carbs, she ran great.

Let her sit for 4 years, got her out again (my 17 year old son has his permit and wants to ride, tough to argue with that), put gas in, checked all the vitals, after cranking for a long time she ran (to my surprise, I expected it to be way tougher than that with my luck).

Now she is starving for fuel. I cleaned the carbs again (they looked pretty good). Starts good, will only idle with 3/4 to full choke after warming up, runs smooth under 4,000, misses at 6,000 unless fully choked. Cleaned the idle jets again tonight, not much changed. Back exhaust manifold got red hot tonight when I was running at about 6,000. Temperature runs on the warm side.

The only thing I can think of is I twisted the tops off the emulsion tubes putting them back in (barely bottemed out and twisted off, maybe I cracked them when I put them in last time). I silver soldered the tops back on, they are not quit square with the tubes, and I managed to run some solder down the jet.

2 questions. Could the heads (tops) not seating completely in the carb cause this problem, and does anyone know the size of the 180 jet on the top of the tube? The standard Mukini 180 jet from what I can find is .085", but my 5/64 drill bit will not go through them (which from what I have found is about .0795". I machined the 5/64 down to fit in the jet and drilled it out, but I am still thinking it may be too small.

Any suggestions welcome, YACS looks good (although when she runs the long hose to the front cylinder collapses).

Thanks.

Gary

[fret not]

start down the list:

fuel filters
fuel cap vent
float level
clean float valves
intake boot leaks
old collapsed fuel lines
fuel pump diaphragms
etc. . . . . .  ;D

[gmac]

Checked the fuel filter when I first started working on, looks clean and gas runs through fine.
Checked the cap already, vent works as it should.
Float level was set right on when I went through them last time, verified it when I had the tops off.
By float valves I assume you mean needle valves?  If so they were cleaned when I had the tops off.
Triple checked for vacuum leaks after putting the carbs back together, including boots.
Fuel lines are like new with no restrictions.
Fuel pump is clean, diaphrams are like new (rebuilt it 4 years ago when I did everthing else) and produces good fuel flow.
Everything I can come up with has been checked, I have working on carbs since I was about 12 (everything from Model A Ford to Tractor to Snowmobile to cars and trucks) so I usually can find about anything.

Any other ideas?

Again does anyone know the diameter of the 180 emulsion jet?

Thanks.

Gary

[Night Vision]

I don't have an 83 emulsion tube or carb handy.. but jet sizes are in mm

a 180 jet is 1.8mm = 0.07086593 inches or a tad over 1/16"

your 5/64 bit is 0.078 inches so it would be a little fat

JasonM is quite knowlegable about 83 emulsion tubes.. he might chime in or PM him

also, did you pull and clean the #50 fuel pilot jets under the carbs?

a rod hot Ypipe indicates excess fuel dumping into the rear carb..

have you sync'd them?

[jasonm.]

Been there done that to the emulsion tubes. Yes...it's 1.80 mm on top. Yes you can solder a replacement head to the tube. Here's the baddest info. You need to get the correct 180 jet from the mikuni list. They are NOT all threaded the same. And can only be bought in groups of 4. I suggest you go to someone who has many types of main jets, hex, round small and round large and see which threads into the carb. I think it's "round large head" will fit...BUT IT SHOULD ALWAYS IDLE IF THE GAS PILOT JETS ARE CLEAR! Otherwise, Your pilots are clogged or passages from them.  http://www.sudco.com/product.html  

[gmac]

From anything I can find the Mikuni numbers indicate flow rate, not diameter (I.E. 180=180cc of fuel/minute). If I'm wrong feel free to tell me. The chart I found says the 180's are 1.92MM which converts to .0765 so yes, my 5/64 was a little over.

Anything I have found indicates these jets are unique to this carb, I spent about an hour at a local dealer that stocks a lot of jets, 180 large are too tall and the threads are wrong, small aren't even close, and obviosly the hex won't work. Couldn't find anything with the right threads (I can fix the height and passage size myself). If anyone can give me a part number for something that will fit I would be eternally greatful and be happy to share the info with the rest of the croud.

Thanks again.

[Lucky]

pm me your address, i might have a tube for you (e-tube right? not the jet?)

[jasonm.]

the jet size is most always the diameter in mm. So 180 is 1.8mm. Numbers do not mean flow rate, because the same jets are used for both fuel and air.

[motoracer8]

 I made air correction jets for my 83 years ago useing Webber air correction jets for a Fiat. I wanted smaller ones for richer mixture. Webber jets are masured by the size of the hole not the flow rate.
The thread size was the same, but I had to remove the emulsion tubes from the OE jets and modify them alittle to work with the Webber AC jets.

   Ken G.

[jasonm.]

I attempted to fix my tubes before I found replacements. These are a statndard metric thread. I believe 5mm. I had some carb sync brass adapters that fit right in. But my attemps failed. I know they are a statndard thread. The exact pitch I do not know. A trip tothe hardware stroe can confirm.