idle mixture adjust screw

[tab1324]

I've read in several threads that people when reassembling their carbs are turning the screw idle mixture screw all the way in, then backing out about 1 1/2 turns. When I dissassembled mine, I turned all the way in which required 3 full turns. Could this be a reason why 3 cylinders look black, wet and sooty? Also the bike backfired and wouldn't stay running.

Should I go back to the 3 turns out or try 1 1/2 to start out with? Hopefully tonight I will put it all back together and try to fire it up.

Thanks again group!

Tom B.

[tab1324]

I meant to also ask about the butterfly setting - I've seen some say to have it all the way closed when first starting the bike, then back out the idle mixture screw about 1 1/2 turns?

This sound right???

Tom B.

[skids]

I don't think so. Step one is to synchronize carbs, which means that you adjust individual throttle plates to equalize vacuum pressures. This may cause some differences in richness because of the exposure of the pinholes in the carb ventouri bores. Then, you make the adjustments to the idle mixture screws on top of the carbs. The colortune tool is good to get you in the ballpark, but coloring new plugs is the final verdict. I think if your plugs are sooty at 3 turns out, you might get away without the synch for now by turning each one a full turn and recheck them with new plugs.

Originally posted by tab1324
I meant to also ask about the butterfly setting - I've seen some say to have it all the way closed when first starting the bike, then back out the idle mixture screw about 1 1/2 turns?

This sound right???

Tom B.

[Midnite]

In or out?

If the mixture is to rich, should I turn the idle mixture screws in, or out?

[wiredgeorge]

The pilot mixture screws can either meter air or gas. That means that if you have one that meters gas, it will reduce the gas in the mixture and if it meters air, you will reduce the air (making the mixture richer) by turning it in. To tell the difference, look at the screw itself. The end of an air mixture screw is generally blunt and the fuel mixture screw generally sharp like a needle. By the way, this mixture screw essentially affects the mixture ONLY in the pilot circuit which is basically the idle and just off idle operation of the carb. If you are "rich" at higher speeds, this is a jetting issue OR it can be that you may have a weak spark that isn't hot enough to clean your spark plug when it fire or possibly the wrong heat range plug. MANY older bikes have poor spark as the path for power to your coils goes through much wire, many old connectors, your ignition switch and kill switch. Needless to say, the ability to conduct electricity isn't as good as when the bike was new. I power the coils on all the older bikes I own directly from the battery via an automotive type relay. In my old 76 KZ900, I have used the same B8ES NGK plugs for the past 13K miles and they still look nice (Dyna S / Dyna coils too).

[nashville_bill]

To answer your question, turn the screws in to make the mixture leaner. They control the flow of fuel in the XS11, not air. However, that probably won't cure "black, wet and sooty" spark plugs. I would think that you probably have float issues.

[skids]

Re: In or out?

If it is too rich, try screwing the pilot screws in a half turn.

Originally posted by Midnite
If the mixture is to rich, should I turn the idle mixture screws in, or out?

[Midnite]

My bike still gets black sooty plugs after countless hours working on the carbs, you suggest here that it can be float issues. I am a novice when it comes to carb work, so could you please tell me what I should do with the floats, raise or lower?
I am about ready to give up and sell the darn thing by now, what sucks is that the bike was running fine until my brother in law rebuildt the carbs because carb 4 was over flowing into the airfilter. He took all the idle mixture screws out and forgot to make a note of where they where set from the bottom, used a K&N carb kit, so after reading the posts here maybe that could be a problem as well??
The floats are now set at 23 mm, and the plugs all looks the same. The bike runs great when I start with new plugs, I took it for a ride today, and after 3 - 4 miles it started to run poorly, and would not run on idle. I got home and checked the plugs, the where clogged with soot.

Thanx guys,
Midnite.

Originally posted by nashville_bill
To answer your question, turn the screws in to make the mixture leaner. They control the flow of fuel in the XS11, not air. However, that probably won't cure "black, wet and sooty" spark plugs. I would think that you probably have float issues.

[TopCatGr58]

Hey there Midnite,

You say, K&N, but I think you meant K&L, which are known to provide the WRONG Pilot jets. If you have your old ones, take them and clean them and put them back in!! IF you don't have them, then you can order them from several places! Mike's XS, Dennis Kirk, etc.! The pilot jets are most likely the culprit, and once you replace them, then you'll be able to get the idle circuit adjusted easily, your float heights sound about right!! I wouldn't mess with them until you replace the pilot jets!!! Then set the pilot screws for 1 & 1/4 turns out to start and you should be good to go!!!

[Midnite]

Yupp K&L was what I was trying to type AND, I was afraid you would say that the jets where wrong! I will try to find the old jets this weekend, I know I saved them, but I have no clue where they are, or if I dumped them later. It has been about 6 months since the rebuild, so I dunno if I can find them or not. It is a pain in the #%% to get the carbs out, so I am not looking forward to that part. My fuel hoses are getting hard as well, so I might replace them with a more flexible kind. Any suggestions on hoses?
Thank you so much Top Cat, I will let you know what happens, can't wait to get the beast running nice and smooth.

Any thoughts on the Yamaha Warrior? I love the looks of that bike so much, read all I can find about it. Probably never will be able to afford one, but I want one really BAD. Anyone here own one, or test rode one please give me your thoughts about it.

[TopCatGr58]

Hey there again Midnite,

There was a thread I posted to a short while back asking about the jets on Mike's Xs and which ones would fit the XS11., I wrote the model #'s and such, can't remember the exact thread right now. If you do find those jets, you'll notice a difference in the number of atomizer holes in their sides vs. the K&L's!! If you can get a short screwdriver, you can pull the bowls and the pilot screws without pulling the carbs off, but will be a bit cramp!

As for the fuel hose, if you don't want to order it, get some from your local MC shop. The stuff auto stores sell as fuel hose is sometimes just vacuum hose, natural rubber that gets hardened with heat and fuel exposure. Polyurethane is the material that is recommended, or synthetic rubber. Good luck!
T.C.
PS, I still LUST after the V-max's myself, but am happy with my little XS11.

[Midnite]

I found lots of jets at Dennis Kirk for Mikuni carbs, but wich ones will apply to my Midnight Special?

"RS?? HS ?? size 60 through 200??"

Does the MS have Mikuni's??

[TopCatGr58]

Hey Midnite,

For the Pilot jets, the BS30/96 series pilot jets, they have the smaller diameter threaded section, and the tapered pointed ends are more pointed, you can see the example in the photos in the Carb tech tips section, Blaine Hoopes FAQ tip!!
T.C.