Topic: Rich idle, how much screw adjustment is allowed?

[scartail]

I've got a 76 550K. I recently opened it up and cleaned the carbs (try to see if there was anything clogged). I set the air screw to 1-1/2 turn from bottom. But I thought it was too rich at idle. I backed it our another 1/2 turn. Better, but there is still some sooth on the plugs. How much more should i back them out? What is reasonalbe, before I really have to look somewhere else?

Details on the bike... stock air box, stock jets, 4-1 exhaust, dyna-s ignition (statically timed). Anything else?

Previously, I had synced the carbs, and adjusted the valves (may have to do them again).

It seems idle fine for a bit, then states to choke up. Fumbles a bit, then catches another good rythm.

Thanks in advance!

[mlinder]

Idel circuit needs to be rich on these bikes, unless they have a accelrator pump, which yours shouldn't.
Leave it stock.

[TwoTired]

When you cleaned the carbs, did you remove the emulsion tubes behind the main jets and clean them?

How old is your air filter?  Is it clean as new?

[scartail]

Thanks for all the responses guys.

TT:

I was just reading your advice to another poster. I seem to mis-identified what the emulsion tube was. I googled it and one description lead me to believe it was the portion opposite of the slow jet with the serie of of holes (radial) and one axial. If it is the tube that the needle sits in, then I have not gotten that deep. I had shot compressed air through, but didnt actually take them out. It's worth a look. Got a picture of this tube?

You need to push out the emulsion tubes and clean them, too.  They come out the hole where main jet was perched.
If they are well stuck, they should be pushed out from where the throttle slide needle enters them.  The emulsion tube also has the slide needle jet in that end. So, when you push them out, be careful not to distort the Jet needle orifice.
If they don't com out easily, you will have to remove the slides from the carb bodies for straight shot access.

Also, you must prove the slow circuit passageways in the carbs are clear.  Pressurized carb cleaner is what I use, with the plastic tube it comes with.  There are four holes to prove in the carb body.  The air jet, the slow jet, the air bleed needle, and the carb throat exit hole.  Fluid must flow from each to one other hole that is not blocked during the test.  Prove that fluid can pass from each hole to every other hole in turn.

Cheers,

[hapakev]

I've got a 76 550K. I recently opened it up and cleaned the carbs (try to see if there was anything clogged). I set the air screw to 1-1/2 turn from bottom. But I thought it was too rich at idle. I backed it our another 1/2 turn.

backing it out would richen up the mix.  turning the screws in would lean it, I think?

[scartail]

I've got a 76 550K. I recently opened it up and cleaned the carbs (try to see if there was anything clogged). I set the air screw to 1-1/2 turn from bottom. But I thought it was too rich at idle. I backed it our another 1/2 turn.

backing it out would richen up the mix.  turning the screws in would lean it.

  Based on the "Carb FAQ"... Out is leaner.

[mlinder]

Like, I said, I dunno the 550 carbs off hand.
If the air screw is on the airbox side, out is leaner.
If it's on the the head side, out is richer, or the dreaded 'I don't do much of anything important' screw. The one that lets in more both air and fuel.

[Inigo Montoya]

IF the 550 carbs followed the same path as the 750 carbs did, 76 and earlier should have air screws that make the mix leaner when turned out.
77/78 made the mix richer when turned out.

[TwoTired]

TT:

I was just reading your advice to another poster. I seem to mis-identified what the emulsion tube was. I googled it and one description lead me to believe it was the portion opposite of the slow jet with the serie of of holes (radial) and one axial. If it is the tube that the needle sits in, then I have not gotten that deep. I had shot compressed air through, but didnt actually take them out. It's worth a look. Got a picture of this tube?

There are two fuel delivery paths for these carbs; the pilot/slow/idle circuit, and the mains throttle valve circuit. They both have emulsion tubes.  They are both located just after the metering jet.  The slow/idle/pilot jet has one machined right on the jet tube.  The main uses a separate larger, tube installed in the carb body and it's outlet end is also the throttle valve orifice, which you have to take care not to deform when pressing the tube out of the carb body.
I do have picture of the tube in my camera.  But, my CF card reader has gone belly up and I can't get the picture in the computer right now. 
I think there have been pics posted before on this forum.  Maybe a search will find it?

Your carbs have an idle air bleed screw that only adjusts the air contribution to the circuit.  Turning out adds more air for more lean mixtures.

[scartail]

I'm about midway way through. I was able to take the main emulsion tube out. The two that I have looked at are pretty clean.

Here's another question... What is the stock needle position for the 76 550K? I swap the exhaust to a 4-1. Should I be concern with changing the position (I'm already in), or just leave it how it is?

Thanks again for all the help.

[TwoTired]

The chart in the carb FAQ says to have the needle in the 4th groove from the top.  Changing exhaust on this bike doesn't usually require much, if any, changes to the stock 022A carb set up. 

[scartail]

Ok, just got through checking all the main emulsion tubes. They were all clean and clear. I'll see how she runs when I throw the carbs back on.

Thanks again everyone for all your help.

[Patrick]

Did you also clear out the holes coming in from the sides of the emulsion tubes?

[TwoTired]

Ok, just got through checking all the main emulsion tubes. They were all clean and clear. I'll see how she runs when I throw the carbs back on.

Thanks again everyone for all your help.

You never answered the my question about the air filter...

[Lars]

If you have a stock 4-4 muffler set on this bike, the circlip to adjust the needle height is to be in the middle of the 5 grooves. If you have a 4-1 muffler, set the circlip on step down to let it run on a richer air/fuel mixture. Just recently I had the same K76 bike in with a 4-1 muffler. We replaced it with stock 4-4, and the engine ran why too rich. I had previously cleaned the carbs well and my first thought was the air filter, but a new filter did not solve that problem. Next i could think of was the needle height, and setting circlips back to the middle position did it all. Lars

[scartail]

Ok, just got through checking all the main emulsion tubes. They were all clean and clear. I'll see how she runs when I throw the carbs back on.

Thanks again everyone for all your help.

You never answered the my question about the air filter...

The filter isn't new, but didn't look bad. I am using a paper filter, so I really don't know if it's clean (though looks clean). Thinking the filter had some effect, I had rode around with the filter off for several days. Though it was slightly better, but didn't have a big effect. But this was a while back. I'll look into finding a new filter.

Lars:

Thanks for your input. I currently have it on the 4th groove. I hope it works out good.