I bought an '85 GS recently and after driving it I noticed that it didn't have the power that I thought it should. It runs well, just doesn't really "get up and go" (my toyota 4x4 smokes it).. I was looking at the carb, and I noticed that when floor the throttle, the secondaries (bigger barrels) don't budge at all. I looked around on the carb to see what is supposed to open them, but couldn't find anything. They are supposed to open right? Is this where my power problem is?

Thanks for the help!

 

They only open under load, so you wouldn't see the butterflies open in the driveway. You could put a vacuum on the diaphragm to test the secondary throttle operation.

 

this will sound kinda vague... but in the back of the carb theres a cable with a little dog-bone style end to it. it just fits into another thingy.... similar to the e-brake cable mechanism at the rear wheels. if this is disconnected, that could be the problem. i know that was vague, but i dont know the terminology.

 

this will sound kinda vague... but in the back of the carb theres a cable with a little dog-bone style end to it. it just fits into another thingy.... similar to the e-brake cable mechanism at the rear wheels. if this is disconnected, that could be the problem. i know that was vague, but i dont know the terminology.

 

damn forum

 

I know exactly what you are talking about.. That was disconnected. I reconnected it and it started running better. What is that exactly? I noticed that it has an adjustment, the "dog bone thingy" screws in and out. What is the proper way to set it?

Thanks for the help guys!

 

Any tips on adjusting the "dog bone" thingy, or what it's for??

 

Good question! How does one properly adjust that part?

 

i believe that you can adjust it to make the secondaries kick in earlier or later. not sure tho.

 

Looking at my Haynes manual........ everyone's got one of those right? I think the "dog bone" thingy is really called a "throttle sub-return spring". I'm not gonna speculate as to what it actually does.

--Bob

 

All I know is that it fell off off it's "shelf" thing, and the car got crappy gas mileage and didn't have any power. once I put it back on, it runs much better. Still waiting to check the gpm.
I have a haynes, but it doesn't say anything about it. Where do you guys have yours set? mine is about halfway now...

 

Unless it's been adjusted before, I would just leave it alone. The thread is one of those locking plastic types, and by design it won't move on it's own.

 

It looks as if mine fell off, then unthreaded itself on it's own. I set it about halfway before putting it back. No plastic locking threads here...
What does it do anyway? I'm sure someone here has rebuilt one of these carbs before.

 

.....waiting for sterling to chime in.......

still waiting...

 

Well guys, I think there's a few guys that are talking about different carb components here! I've been watching this thread scratching my head, and saying to myself, "O.K.- some people think you know about these carbs, so don't say anything stupid now, Sterling..."

Well, I jess dunno!
I think specRX 22 is talking about the throttle cable!
I think mgw24, Gamble and inittab are talking about what I refer to as the "emergency" throttle return spring mechanism.
It is my understanding that this has the ability to adjust throttle pedal tension (feel), but also serves to close the throttle should your main spring come undone, break, ect.
I think supraslinc is talking about the accelerator pump adjustment nut. This is a long, tiny cylindrical aluminum nut with a blue Nylar plastic insert and threads over the rod that sticks out the AP lever hole. Threading this clockwise will give more pump-shot; going the other way does the opposite.
Don't mess with it unless you feel you need to tune the carb and the AP, specifically.

...Anyway, none of these things has anything to do with how or when the secondaries will open. They can only open when the throttle is at least halfway depressed, and not fully untill the throttle pedal is fully depressed. Anywhere's in between, it's up to the vacuum of the engine as to how far the secondaries will open. The vacuum increases substantially under load (up hill, trying to pass, driving like inittab, ect). There's a spring attached to a diaphragm in the vacuum box (light duty) that has to be overcome by the vacuum. A little "curcuit" or passageway goes from one side of that diaphragm to the body of the carb, and comes out into the forward facing primary venturi. You can see the hole. If you were to tape it shut, your secondaries would never open. (The tape would probably peel off and get sucked into your engine, so don't try it!)
By the same tolken, if the vacuum box is not sealed well, then the vacuum signal that is pulling the diaphragm against the spring will be bled off some or even non existant.

The diaphragm has a metal center which pushes a rod under vacuum signal. The rod is hooked to the linkage, and the linkage is hooked to the secondary shaft.
The secondary shaft CANNOT open until the primary shaft opens a certain point, and releases tention on the business end of the shaft. There's a spring wrapped around the secondary shaft that holds it closed. When the primary shaft opens far enough, a tab on that shaft pushes against the tab on the secondary shaft retaining spring, and releases the tension. Then it's up to the vacuum box.

...I'm tired of typing now.

 

Try giving the rod a little push with your finger while someone else gives it a little gas. I say give it a little gas becuase if you just try to push it you will have to overcome the Primaries linkage, spring and throttle cable while you are pushing on the little rod. BTW dont be suprised when your RPM's jump up like there is no tomorrow. I had a carb that I did this on. the secondaries were stuck, carb had been sitting a long time. I felt the resistance then it just let go. after that everything moved smoothly.

...Sean

 

Cool, thanks for the help all!

 

no im definately not lol.

 

the thing im talking about definately has to do with the opening of the secondaries. I had this guy Phil who a head mech. at a Mazda dealership find this problem on my dad's car. its not supposed to move or anything... it just sits there and provides resistance.

 

interresting... The car did run better (more power) with this "thing" hooked up...