Anyone ever leave the air screws alone?

[kilog55]

yes the little needle screw that is tiny in front of the opening of the inlet of the carb. hopefully that is clear. the one with the rubber plug in front of the carb float you seat all the way down

 

[oldgsfan]

This is where I go.. ohhhh, now I get it..

thanks, man

 

[kilog55]

yeah it is confusing since that little screw has so many names on different carbs for us it determines leaness and richness of the fuel. for some it means how much air goes in.


but this site is great for anything you ever need to know about the GS

 

[oldgsfan]

i could not have done half of what i've done on the bike without the help of this website.. it is absolutely fantastic, as are all those who contribute to make it what it is..

 

[reddirtrider]

If they're coming out real hard you may have some metal shavings left from drilling out the plug. Turn them back in slightly and use some carb spray to clean the threads, or PB Blaster. Take it easy. If you mess them up with too much force you're not going to be happy.

 

[Steve]

Thanks - I have been having a problem following some of these carb threads and how-to pictorials. Seems that some people refer to them as "Air" screws, or "Pilot" screws, or as "Idle Mixture" screws.

Does the terminology change depending on if one is working with a CV carb verses a VM carb? Or is the terminology constant accross the industry?

OK. to make sure, the air screw that i'm thinking of is the screw on the outside of the body that is covered by the aluminum plug (which, by the way, is a real pain to remove).

the pilot screw, I thought, was on the inside of the carb body where the floats are.

so my earlier question was whether this second screw, that I saw referred to as a pilot screw in the tutorial, whether that one needed to be unscrewed 2 and a half turns after being seated..

as opposed to the air screw, on the outside of the carb body, which, if I'm understanding correctly, should be backed out 1 and a half turns after being seated..

and, by the way, that is a real, real, real big pain.. i'm having a heck of a time getting them out and even getting them back in.. ugh. so far, absolutely the worst part of this carb job has been messing with these air screws..or, i mean, idle mixture screws.

Yes, the terminology and the function change, depending on whether you are working on VM or BS carbs.
By the way, "CV" is a type of carb, "VM" and "BS" are two models of Mikuni carbs that are used on Suzuki GS bikes.
The BS series just happens to be a CV-type carb.

On the VM carbs, there is a pilot fuel screw on the bottom of the carb. There is also a pilot air screw on the side of the carb. Both of these are adjustable. On the BS carbs, there is a non-adjustable (but replaceable) pilot air jet in the intake of the carb, and there is a non-adjustable (but replaceable) pilot fuel jet in the float bowl (behind the rubber plug, next to the main jet). Together, they pre-set the idle mixture. The idle mixture adjustment screw on top of the outlet of the carb will control how much of that preset mixture is allowed into the air flow.

When assembling the carbs, all other jets, screws, whatever, should be installed snugly. Hope this helps.

.

 

[oldgsfan]

Yup, that does help clear it up for me. I think I've got it now.

And I'm certain I've got the BS model carbs.

My idle mixture screws are not seating to the same depth on all my carbs, however. Is that normal? This is the first set of carbs I've worked on so I'm not sure how they're supposed to look.

In this case, the idle mix screw goes down deeper in my number 2 carb than in my number 1 carb. I removed the screw on the No. 1 carb, cleaned out the channel with some carb cleaner then blew it out with some compressed air, on the chance something was preventing the screw from going any deeper. But it didn't change anything. The screw just doesn't go in as far as on the No. 2 carb.

I can't tell about my number 3 carb because I have yet to be able to remove the screw in the first place! And, yes, it's starting to get a little mangled so I'm starting to get pretty worried I'll never get it out at all.. ugh.. i hate these damn screws!

I soaked the idle mix screw on the No. 3 carb over night with PB blaster, but that didn't help..Other posts have suggested applying some heat to the area to help loosen things up.. I have a neighbor with a torch set up I'm sure I could use but I'm not sure what the technique is...do i direct the heat onto the head of the screw, or just outside the opening?

Any help, as always, is much appreciated.. these screws are just freakin' killing me..

 

[pdqford]

By the way, "CV" is a type of carb, "VM" and "BS" are two models of Mikuni carbs that are used on Suzuki GS bikes.
The BS series just happens to be a CV-type carb.

Ah-So! The "CV" stands for "Constant Velocity" type of carb, as in it has a 'slider' to vary the venturi size so as to maintain the velocity as constant over different air flows.

The "VM" model's slider is mechanically operated, while the "BS" model's slider is vacuum operated.:dancing:

That really helps me get oriented to this lingo!

On the VM carbs, there is a pilot fuel screw on the bottom of the carb. There is also a pilot air screw on the side of the carb. Both of these are adjustable. On the BS carbs, there is a non-adjustable (but replaceable) pilot air jet in the intake of the carb, and there is a non-adjustable (but replaceable) pilot fuel jet in the float bowl (behind the rubber plug, next to the main jet).

Again, Ah-So! If it's proper name is a 'screw', it is adjustable and not installed in the seated position. If it's proper name is a jet, it is fixed and installed in the seated position.

Thanks. That helps me big time!

 

[oldgsfan]

So, still working on my carbs.. it has become my life.

Anyway, my idle mixture screws are not seating to the same depth on all my carbs.

Is this normal? I don't recall what they looked like before.

On my No.. 2 carb, the idle mix screw goes down deeper than it does in my No. 1 carb.

So, I removed that screw, cleaned out the channel with some carb cleaner and gave it a shot of compressed air in case something was preventing the screw from going any deeper. But still, it just doesn't screw down as deeply as the No. 2 carb air screw.

Just wondering if that's to be expected or if I need to worry about this.

 

[reddirtrider]

How hard did you turn them? They only need to be lightly seated by using your fingertips. They should all be at about the same level.

 

[oldgsfan]

Thanks, man.

Can't really use my finger tips cause they're set in a well at few mm deep.

But, yeah, i figured they should all be around the same depth in there..

The No. 2 carb screw went in without any difficulty. That's why the no. 1 is a real puzzle to me..I'll try cleaning out the channel again..

Though I'm beginning to think I may have messed up the threading on the idle mix screw and maybe should just order a new one.. as it is, my no. 3 is stuck, so I'm probably gonna end up killing it anyway just getting it out .

guess i'll order TWO new ones..

OK.. Thanks for the help.. much appreciated.

 

[reddirtrider]

Thanks, man.

Can't really use my finger tips cause they're set in a well at few mm deep.

But, yeah, i figured they should all be around the same depth in there..

The No. 2 carb screw went in without any difficulty. That's why the no. 1 is a real puzzle to me..I'll try cleaning out the channel again..

Though I'm beginning to think I may have messed up the threading on the idle mix screw and maybe should just order a new one.. as it is, my no. 3 is stuck, so I'm probably gonna end up killing it anyway just getting it out .

guess i'll order TWO new ones..

OK.. Thanks for the help.. much appreciated.

Finger tips on the screwdriver to seat them and they shouldn't require much to run them down either. If you must force them, they're probably cross threaded.

 

[oldgsfan]

Oh.. i get you now..yes, the no. 2 was that easy.

thanks again

 

[SneakyPete]

I am having a similar problem as OLDGSFAN on my '82 Shaft Drive 2 valve 1100.
I just rebuilt my carbs. The previous owner(s) have messed with the carbs in the past. The screw head in #1 was stripped and I couln't get it out. #2 the screw wouldn't seat as far down as #3 & #4. What should I do? Should I adjust #2, #3, & #4 as close to #1's depth as possible? I dont see any other recourse, excepct to drill it out (I don't have a drill press or the ability to fix the threads that are probably mangled). The bike does have a V&H 4-1 and a K&N filter in the box, I don't know if it has a jet kit, but I didn't see and Dynojet markings on the jets...

 

[reddirtrider]

I am having a similar problem as OLDGSFAN on my '82 Shaft Drive 2 valve 1100.
I just rebuilt my carbs. The previous owner(s) have messed with the carbs in the past. The screw head in #1 was stripped and I couln't get it out. #2 the screw wouldn't seat as far down as #3 & #4. What should I do? Should I adjust #2, #3, & #4 as close to #1's depth as possible? I dont see any other recourse, excepct to drill it out (I don't have a drill press or the ability to fix the threads that are probably mangled). The bike does have a V&H 4-1 and a K&N filter in the box, I don't know if it has a jet kit, but I didn't see and Dynojet markings on the jets...

Try putting a VERY small dab of epoxy on something like a bolt or nail that's filed flat - something that will fit into the recess- let it dry then use it to unscrew the buggered up needle. Be careful how much epoxy you use as you don't want to get it everywhere - only on the head. Use some spray carb cleaner to prep the surfaces.

 

[oldgsfan]

Well, just got new air screws in the mail from Z1Enterprises and, wow, what a difference that makes!

The old screws, even when I got them out, were a real struggle to get back in! I guess I must have messed up the threading on them during the ordeal.

Anyway, the new screws went in very smoothly and with no problem, seating easily in the bottom of the well, and easy to back off the suggested turn and a half.

If I had to do this over, I would have ordered new screws same as ordering the o-ring package. Seems to me it's well worth the $8.55 per screw price to save a little aggravation.

Now, I just have to get that danged fuel mix screw out of my No. 3 carb. It has become the bane of my life.

I finally got that stubborn screw out. I did what other posters on the forum have done - used a dremel. I cut the tower down until I could reach the head of the screw, cut a deeper slot in it and then, very carefully and slowly, managed to muscle out the mangled screw. It was sketchy there for a bit.

I sprayed the interior with carb cleaner and some compressed air to make sure there were no metal shavings. A new fuel mix screw from Z1 went in quite easily.

But, now, it turns out, I'm short one good screw. Guess I gotta make another order. Sheesh. But at least I feel like I'm on track to get these carbs done one day soon! Totally thrilled about that!