"residual casting sand that filled the "off-idle" bleed holes"

[Jimustanguitar]

I am cleaning my carbs this weekend. Which holes are the "off-idle" bleed holes that are referenced as a possible problem in the wiki? There are some teeny tiny holes near the butterfly, I believe there is a cluster of 4 of them, as well as a single hole that is a bit larger...  If anybody has more information about this possible manufacturing defect, I'd like to know what to look for and how to deal with it.

I'm planning to do a cautious dip, and then blow out all of the passages that I can with compressed air. I also have a little ultrasonic cleaner that I'll clean my jets and venturis with. Probably get out the old garage toothbrush too. Should I chase the little holes with a guitar string or something like that?

BTW, I've read a lot about the other possible stumble causes discussed on the forum and am aware that I could have a dozen other tuning issues contributing to this one symptom (my carbs need to be cleaned anyway, so it's not a fool's errand even if I don't solve my stumble with clean carbs). If cleaning these downdrafts doesn't do the trick, I'll just keep moving down the list. Hopefully my voyage is bon :)

Thanks for the input!

[Lucky]

all the holes you describe by the throttle plates are supposed to be there. Don't believe everything you read on Wiki. I woildn't run anything thru the tiny hiles. hate to see a piece if guitar string break off in there., otherwise, dip away.

[Rikugun]

I don't think Jim is asking if the holes belong there but rather if they are the air bleeds referenced in the Wiki article. In answer to your question I don't know but I doubt it. I tend to think of air bleeds being in the air horn and feeding air to a circuit that is also fed with fuel from another passage.

Like Lucky said I wouldn't put a lot of stock in that reference. All the passages are critical and some on theses carbs are difficult to effectively clean. Running wire through jets and passages is not recommended as it can alter the shape size and flow of some critical openings. Having said that it's often done anyway so be carefull.  :P Carbs dips and the ultrasonic cleaner is your best bet. Even using these methods some find more than one cleaning is needed on especially troublesome carbs.  :(

[The Prophet of Doom]

The original article was from Marc at Factorypro
http://www.factorypro.com/prod_pages/prodyXZ550.htm

It makes for a great story - Marc the factorypro tuning hero discovered what was baffling the retarded Yamaha engineers for ages, but I think that is all it is - a bullshit story he tells to make his dick look big.

A) You can clearly see on the carbs where the passages are drilled, and the drill entry point sealed up.
B) there is no way to get a drill in there once the hole on the opposite side of the carb is sealed - they are too far up, and
C) there is red crap in every vision carb I've stripped including in the accelerator pumps - it is rust from the fuel tank and fuel deposits, not casting sand.

The message is the same though, blockages in these small passages will cause you problems. 

I found that dipping (without ultrasonics as I don't have one) did not get it cleaned out.  I resorted to compressed air and cans of carb cleaner from both sides.  It took some time before all 4 holes gushed freely - the amount of crap that came out was astonishing.

[Rikugun]

I found that dipping (without ultrasonics as I don't have one) did not get it cleaned out.  I resorted to compressed air and cans of carb cleaner from both sides. 

Agreed roro.  I left that step out 'cause I assumed everyone does that as the last step in the cleaning process.