carb modification question

[dbeardslee]

I know there are threads on here someplace that talk about modifying 80/81 carbs by installing a mixture screw. Thought it would be in tech tips but, alas, not. I've looked high and low and can't find the info. Anybody have or know the procedure? Also, I have a set of mixture screws that came out of some 78/79 carbs - will those work for this mod?

[TopCatGr58]

Hey DB,

I'm not familiar with any MOD for the carbs you mentioned??

The earlier idle/pilot screws will not work for the later carbs. About the only mod I now can think of is for the vacuum slide needle, putting a few washers under it to shim it higher making it richer sooner in the throttle response range!?
T.C.

[The Lorax]

Hey Doug, there are mixture screws in the 80's vintage carbs, you just can't see them because they're hidden under a set of plugs in the towers. get the plugs out and you'll see them. some drill a small hole in the plugs (a little bigger than the one already there, but if not careful, you can bugger up the top of the screw as the drill passes through the plug, then run a self tapping or sheet metal screw in the hole and pry out the plug with a screwdriver or something) just look between the diaphrgm cover and the intake boots on the top, you'll see a brass plug in front of each diaphragm cover, they have really tiny holes in them. be careful with the drill though, can't stress that enough. and the screws are stepped down in diameter, not tapered like yours. questions, feel free to give me a call. have a nice day and ride safe

[oldyam80sg]

Has anybody put on any carbs like Mikuni smooth bores.Friend of mine installed them years ago on his Kawasaki and said they were the stuff to have!

[dbeardslee]

TC - The Lorax got it - sorry for my poor communication skills, but at least my search skills are still intact - no wonder I couldn't find it.

Matt - I saw the plugs you mentioned, and figured they would have to come out. Didn't know there were mixture screws underneath. I'm actually asking for Eric as he seems to be having a problem with the mixture on his. Thanks for putting me on the path, brother.

I've got several carb bodies off an 80/81 to experiment with, but even so I didn't want to tear something up for lack of asking.

TC - Wouldn't this procedure be something that would be a good addition to the tech tips? If you think so, I can take some pictures.

[TopCatGr58]

Hey Doug,

Well, I didn't consider the brass caps as a MOD, just a necessary step in both cleaning and then tuning those years of carbs!

Yes, we would appreciate a nice set of photos to document this. This is just one of many tech tips I've had on the back burners for quite some time! If you do a nice enough writeup, I'll even post it with your "byline"!

If you search for brass caps you might even find the threads where both myself and others have posted the directions on how to do this.
T.C.

[dbeardslee]

TC - I'll get some pics for you. I couldn't wait, and took one of the bodies I had in the man cave, and it came out pretty easy. One thing I noticed - I kept drilling progressively bigger holes, and on the last one the drill bit snagged and popped it right out. Makes me wonder if I slot one with a dremel tool, if it they might not come out easier by just twisting. I've got two more to experiment with, so we'll see.

[The Lorax]

Yeah Doug, the guy at the boneyard I bought my carbs off of told me about the brass plugs. I actually buggered up the screw in #4 carb, ended up cutting away a piece of the tower to get it out for replacement. I don't mind telling the world I'm a pinhead, better someone learns from my foul ups and saves themselves a few bucks or a lot of aggravation. I figured it was for Eric's bike as you guys have been talking carbs a bit lately. let me know if I can help at all. Have a nice day and ride safe

[dbeardslee]

let me know if I can help

Matt - for some reason that line reminded me of the scene from Return of the Jedi, where Darth Vader has just s**t-canned the emperor and he tells Luke to leave him. Luke says "I've got to save you." And Darth replies "You already have." Thanks, Matt/Luke.

[The Lorax]

I was never THAT pure, or knightly for that matter...more of a scroungy bast... depending on who you ask in any case, most anything for a fellow XSive. have a nice day and ride safe

[egleaves]

I've got two more to experiment with, so we'll see.

Is that counting the set on my bike?

No, I don't think it is. I can't tell you how much I appreciate you doing all this research and experimentation on my behalf. I already owe you a few beers, but if you keep it up I'll have to throw a steak in there too!

[dbeardslee]

Is that counting the set on my bike?

Veeeeery funny. I have three carb bodies in the man cave that were left over after I cannibalized them for plastic floats. I completely dissassembled them (with the exception of removing the mixture screws, which obviously I didn't know were in there.), cleaned the parts and set them asside in case they were needed. I wouldn't think of tearing into someone else's machine unless I was sure I could obey the hippocraticratic oath for mechanics - don't f@#$ it up any worse. Don't worry about beer and steak (although those are my two favorite food groups ) - I've been wanting to get better acquainted with the 80/81 carbs anyway.

On the one which I have already removed the mixture screw and spring - they looked just like you would expect for a carb part that has been in place for 29 years - pretty cruddy. I'll take some 'before' pictures of them for all to see. When we adjust them we may have to remove the tank (or at least lift it up off its mounts), as I don't think my carb tool will reach down inside that tunnel. Whatever it takes. I just want to see it running like it's supposed to. My only full time job these days is taking care of my 85 (soon to be 86) year-old mom, so I'm always looking for things to occupy my mind and my time.

[DGXSER]

Don't worry about beer and steak (although those are my two favorite food groups ) - I've been wanting to get better acquainted with the 80/81 carbs anyway.

Dang Doug, I was going to volunteer to come help you out and get in on some of that beer and steak action!! I bet we could get the whole group to work on them for that price!! Seriously though, as I have been through my carbs fairly thoroughly, be glad to offer any help I can.

[dbeardslee]

Don - Your help is always appreciated. I just got a PM from Eric, and it appears we are going to attack his carbs this evening. If you'd like to drop by I'm sure we can all find something to do. Confucius say "Many hands make light work." I promised TC pictures for a tech tip, so if you want to be immortalized on digital film, stop on by. I'll pm you directions.

[fredintoon]

- - Matt - I saw the plugs you mentioned, and figured they would have to come out. Didn't know there were mixture screws underneath. I'm actually asking for Eric as he seems to be having a problem with the mixture on his. - - -

Hi Doug,
if those factory-installed plugs are still in place there's gotta be 29 years-worth of crud in and around the mixture screws.
Be careful removing those screws, there's a spring, a flat washer and an o-ring on them that has to come out too.
If those parts stay down the hole when the screw is removed, hook them out with a modified paper-clip.
Pull those fat brass enrichener circuit plugs too. The little holes behind there are also part of that system and will also need cleaning.