Weber 32 DMTR Idles By Itself!

Joshua Stinnett

Joshua Stinnett

Daily Driver
So I just replaced the fuel pump on my '74, replaced the fuel filter and cleaned the carb filter, as well as replacing the top gasket for the carburetor. I set my carburetor to base settings (2 turns on the mixture screw, 1 and 1/2 on the idle) and it idles at around 1500 rpm. I backed the idle screw out entirely and it idles consistently at 800 rpm. I took the top off again, cleaned the jets thoroughly, sprayed cleaner into the jet holes and throughout the carb, and put it back together. It still idles by itself with the screw totally out. Does anyone have an explanation for me? It's really starting to drive me crazy 0.o
 
Josh,

A lot of things contribute to a good idle. I'd say, if you are at 800 revs with the idle screw backed out, your carburetor is ok and no vacuum leaks.

Mixture is not a 2 turns out deal. It needs to be set for the desired rich or lean running condition. If you don't find a guide by searching here, I think Pierce Manifolds has a good description of how to set a good idle. You have my number. I can walk you through it.

Ignition timing and choke operation can affect idle also. Choke seems to be out of the picture if you are at 800 rpm. I generally set idle at 850 rpm and ignition timing at 10 degrees advance for stock applications.
 
Thanks Ernie, will do. I'm about to go for a quick drive and see how it goes. If it doesn't starve for fuel again, I'll considering this a win. I set the timing to stock after I shimmed the valves, so hopefully everything is okay.
 
rachaeljf said:
Which screw have you backed out completely? You suggest the idle stop screw.
Click to expand...
That's the one. Idle mixture screw is in 2 turns and the idle stop screw is backed out so that it's not coming into contact with the throttle lever. It seems to be driving fine, but in my limited experience with Webers I've found that the idle speed screw is supposed to be set in at least partially.
 
If the engine is otherwise running fine then you have something stopping the one or both throttle butterflies closing fully. This could be the choke mechanism not being fully off, or the throttle cable assembly being too tight. I could also be a misaligned butterfly if you have taken it apart to that extent.
 
Might you have a very early 32 DMTR? In these the idle is not controlled by the idle stop screw; the butterfly closes completely and the stop screw just keeps it from banging into the side of the barrel. Idle air flow goes through a bypass passage inside the carb, and there's a third screw (center, halfway up) that limits flow through this passage to control the idle speed. It's #44 in http://xwebforums.com/wiki/images/f/fe/32DMTR.pdf
 
any updates have u checked the carburetor hasnt warped on the sealing surfaces between the float bowl and the top part
 
Ollie said:
any updates have u checked the carburetor hasnt warped on the sealing surfaces between the float bowl and the top part
Click to expand...
Sorry, I didn't realize I never gave an update. That's exactly what happened Ollie. One of the spacers for the air cleaner fell out and directly into the bottom half, which stuck out just enough to bendthe top and bottom of the carb when I tightened it down. I ended up having g to get a whole new one. A few hundred miles later and everything is back to normal. Thanks everyone for the input!
 
You must log in or register to reply here.
Back
Top