bike suddenly started idling rich

[fyrman41]

So I though I finally had my bike tuned properly. It was pulling hard and running great. No it idles as if the choke was partly on. Just to keep it running standing by itself the idle screw needs to be almost all the out. The midrange on up run smooth but dont seem to pull quite as hard as before it acted up. I tried going down to #30 pilots with no change. Pull the vacuum tubes off the barbs and she will take off to 1500 rpm. The mixture screws have very little to no effect. Ive checked the floats several times making sure they are at 24mm and not bent or pushig down on the needle. Floats are good and have no cracks, needles dont leak. I got fuel the night before it started. Pit Stop 91 octane ethanol free gas. Could it be Bad gas? I cleaned the carbs up making sure every single passage way was clear. Even the air jets. IUed carb cleaner. Even tried new pulgs, and it blackened them in a hurry. Maybe weather change? High 70s to high 80s with lots of humidity. Im very stumped and frustated. Both carbs or do8ng the same thing but the left a bit more than the right

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[retiredgentleman]

As a test, try removing the pod filters, and running the engine. Some of the pod filters are known to cover up the small holes that allow air into the jets and emulsion tube.

 

[fyrman41]

Tried running it without the pods. Still runs the same It chikes even more if i put my finger over the ilot air jet so i must not be plugged.
Now when measuring the float height. I measured it with the tang just touching the tip of the needle valve, I see 5twins measures it with the float resting right on it. Should I try that?

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[retiredgentleman]

Tried running it without the pods. Still runs the same It chikes even more if i put my finger over the ilot air jet so i must not be plugged.
Now when measuring the float height. I measured it with the tang just touching the tip of the needle valve, I see 5twins measures it with the float resting right on it. Should I try that?

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5twins is the carb expert on the site, so I would always follow his directions.

I'm not a carb expert, but I suggest you go back to stock jetting, and stock needle position.
MJ 135 and PJ 27.5 to see how that works for you.

You can then increase jet size, 1 step at a time, if needed.

 

[TwoManyXS1Bs]

Some more thoughts:

http://www.xs650.com/forum/showthread.php?t=33757

Some snippits from other posts:

A cheap addition to your tuning toolbox is the petcock(s). There's about one minute of fuel in the float bowls. Switching the petcock(s) off during a carb evaluation, and knowing that the fuel level will drop during the test, and observing what happens when, can add insight to the carb tuning matrix...

Back to your problem. One thing you could try, after you get it back together, is to turn off the fuel delivery to the carbs after it starts, so it's running on just the fuel in the bowls. As fuel is used, the fuel level will slowly drop. If the engine runs continuously better, then you may have identified an overfill condition, caused by bad floats, float valves, height setting, crack/leak in carb body, warpage of carb body, ...etc.

Here's an el-cheapo test. Turn off the fuel petcock(s) during your ride, and see if conditions change during bowl depletion. If, after a few seconds, it clears up and runs fine for awhile, that may indicate too high a float level. If not, could indicate jetting problems, or something ignition...

 

[gggGary]

So I'll ASSUME these are 78-79 BS38s. You have not mentioned that you have gone through the enrichers, removed the plungers checked the ends are smooth, no crap there keeping them from sealing shut? I have a slightly burbly hunting idle on the 79 resto and need to check them myself.

 

[weaselbeak]

Whenever someone uses the word "suddenly", I think of sticking floats, as in maybe a little dirt or something got under a needle. Why mess with jetting when it ran fine to begin with?