Adjusting the Idle Mixture on CV Carbs

[pete]

Very enlightening... thanks again George!

[koolaid_kid]

We exist only to serve. (LMK if you know the book that quote came from.)

[BigD_83]

We exist only to serve. (LMK if you know the book that quote came from.)

My first thought was an Aasimov story,but now I'm thinking something much drier...and set more in an apocalyptic future/parallel universe...wink me a blue eye if I'm close

[koolaid_kid]

Wink wink

[Frank Z.]

Great info, KK. Thanks!
Just added to my subscribed links

[john82q]

KK great info,
JUst a suggestion, how about combining some how it works theory into the indroduction for your procedure?

And a picture for the "Visual Learners"

This picture from the manual is a good start, but it would be great if someone with the image manipulation/creation skills and time, could make one in colour without the cross hatching so its clearer.



oh and I like Mr Herberts work too...

[loud et]

You are right John 82. Chuck H had put up a carb theory article that was a good read but long and I got bored. IIRC it was not CV's either but general carb theory.
After seeing your post above I recalled this info is in the service manual, which it looks like you may have used for your reference.
Anyways, thank you all.

[koolaid_kid]

As I indicated in my post, I found a web page and filtered through all the extraneous crap and just gleaned what answered loud_et's question. It may have been the same stuff that Chuck H had posted, because it did have a lot of general carb theory, which was not germane to the request.
It would be more appropriate in the Appendix. That way, someone who just wanted to get the mixture screws set correctly can do it quickly and easily and not hurt their brain. Those more interested in the theory could dig into the Appendix to understand it.
I have no image manipulation skills, so someone else would have to do that work.

[Gorminrider]

Thanks,old_skool. The ol' gs400E Im tinkering with has "hanging idle" throttle and this will get to the "things todo first and in order" really quick and concise.

[azr]

Just subscribing to the thread to read later. Good info.

[luvnwunderwoman]

Thanks for posting, this thread is a must read for all of us noobies.

[GSOH]

Thanks for sharing this. I need to do this to my bike tonight. Sounds like it may be easier/more effective than each screw by itself.

My main debate is deciding whether to make my old temp fuel supply off the bike so I can adjust the screws with the tank off.

[AJ]

I've posted links about carb tuning before. The chart below helps explain the relationship between the various systems and how they work in various throttle positions. Here's where I pulled the current pic from (http://justkdx.dirtrider.net/printcarbtuning.html). Looks like the entire article was copied from elsewhere.

If I understand the KK's approach correctly, the key thing is that:
1) overly lean low-speed mixture will make the idle hang a bit (or be slow to return to idle) when you blip the throttle
2) overly rich low-speed mixture will make the idle sag a bit when you blip the throttle.

Makes total sense, not that I have tried it.

Last thing to be mentioned: On a 4 cylinder engine, it's really best to adjust valves first, then tune carburetors, then synch carburetors. Especially be sure to do the valves before synching or you may be misadjusting your throttle plates to compensate for a poor valve adjustment.

Mikuni has a nice guide to carb adjustment here: http://www.mikuni.com/fs-tuning_guide.html

[1948man]

Should a carb sync be done prior to the mixture adjustment or after?

[Steve]

I think a carb sync should be done BEFORE a mixture tweak.

Look at it this way: if one carb is out of sync and happens to be closed, tweaking the mixture won't do much.

If you make sure that carb is flowing the same amount of air as the others (by matching the vacuum levels), you will know that the mixture tweak might have a chance.

EDIT: I just went up a bit farther and read AJ's post, Have to agree with some and dis-agree with some.

Yes, adjust the valves before synching the carbs.

No, sync the carbs before adjusting mixture. Reason already stated above.

By the way, some of the items listed in that chart might be a bit confusing, because it is for the VM carbs, not the BS-series CV-type carbs.
Other than that, it's a good chart. I will have to read the rest of the article when I have some time.

.