Carburater woes, idle adj screw

[eltoroloco]

I have a 1980 g that wont idle well. It back fires, wanders around rpms. Sounds great reved up but doesnt fall back to idle fast as it should if at all.

I know its running rich from the look of the plugs and the gas stench the thing gives off is obvious.

Is my mac 4-2 exhaust causing the rich mixture. Do i have to re-jet?

My neighbor thinks i need to re-adjust the idle mixture screws. As well as clean them out well, (2 pilot jets were clogged) Theres only one problem with the idle screws, cant find em. I have a clymer manual that shows them clearly but my carbs have a brass cap with a small hole in the center.

Theres a screw just under the spring that snaps the throttle back, is that the idle adjustment screw?

I've tried synchronizing with a mercury gauge, but no go. Any ideas?

[dragxs11]

Hi Eltoro, You've found the idle adj. screw, yes....It's in the middle front on the bottom of the carbs. with goofed up carbs your idle may be set high enough to keep vacume on the timing advance, I bet thats the problem with your r's wandering. The idle mixture screws are located just in front of the diaphram caps on the tops of the carbs. unless they've been tampered with, they sit under little aluminum plugs with a tiny hole in each one. These you have to drill out to get to the screws. They are factory set, and your not supposed to have to mess with them. But if they're clogged, you have no choice. Your float needles in the carb bowls may be bad(common issue) causing too much gas to force it's way into your carbs while running. The vacume valve that shuts off the fuel when the engine turns off may actually be working so that you don't see gas on the floor. Thats just an idea....take it for what it's worth.

[eltoroloco]

sounds pretty drastic, drilling holes in my carbs. But what the hey, another excuse to bust out the power tools. Thanks for the advice.

[TopCatGr58]

Hey there "Crazybull",

Those caps are brass, not alunimum! Take a modest sized drill bit that will make a hole just big enough to screw in a 1" sheet metal screw into it! Go slow, the cap is about 1/8" to 3/16" thick, and the pilot screws are just below it, so you want to be able to tell when you just break thru the cap without diving into the pilot screw and messing up the screwdriver slot! I put a piece of tape around the drill bit about 1/4" from the tip, that way I can see how far I've gone!

Then screw the sheet metal screw into the cap, then grab the screw with a lockjaw pliers, and then tap against the pliers like a slide hammer to pull/pop out the caps! There are several little metal and rubber washers and a spring on the end of the pilot screw, so be careful not to loose them.

Your exhaust might actually be causing a lean condition due to better breathing!? Once you adjust the MAIN idle screw, the one in the middle of the carb bank, along with cleaning the pilot circuits on all of them, you may find that it will idle. Then you can adjust the idle speed down to near the 1k mark, and then you should be able to synchronize them with your gauges!
Good Luck.
T.C.

Thanks pgg, editted!

[dragxs11]

Oh, I guess maybe they are brass....Funny, I haven't seen a gold tint to any of mine.....Anyway, I think topcat meant tape around the drill bit, not tap. You could put an eye out that way .