won't idle, looking for expert advice.

[shorty402]

Afternoon all. I have a 69 swb 402/t400. Cant get it to run at idle. If have to hold throttle to about 2k and hold choke almost completely closed to keep it running. Accelerator pump works fine. Im thinking idle circuit not working or possibly a huge vacuum leak. I am going to take carb apart and clean and look for any obstructions and plug all vacuum ports on carb and intake. Any other suggestions would be greatly appreciated.

[Steeveedee]

Plug all the vacuum ports before you tear into the carb. That would include the ones on the intake manifold. If it runs OK, swap the lines back on until it goes crappy again. If not, you know what to do.

[shorty402]

Thanks for the reply. Already have carb off. Its been sitting for quite awhile with old gas and should be gone through anyway. Will plug everything before trying to start it again. Can't even time it like it is now.

[oneshotkyle]

Vacuum leak

[1967GMCC20]

Agree - Vacuum leak... clean carb, inspect mounting flatness.

WD40 spray around carb base usually can find.

[jabborabbo]

Carbs are built by elves that live in the Black Forest of Germany ((right next to the Keebler Cookie Company)…I would check EVERY orifice/passage in the idle circuit for obstruction… I have personal experience with clogged orifices/passages…and ain’t NONE of them been pleasant….

[54blackhornet]

I had a Stihl chainsaw that would not run properly. Had the carb cleaned by an ultrasonic parts cleaner. Cured the problem.

[shorty402]

Will be taking carb apart tomorrow, it will be raining all day anyway.
I will report back with any findings. Thanks

[1967GMCC20]

Working on, and resolving carb issues is good therapy. And when your good at it, you'll be the guy to fix everyone else's.

My buddies junk carb, he gave me, now runs like a top on my 402BBC.
All I did was scrape out the chalk from dried out fuel remnants.
Elec choke is nice.

[Dashman]

It's getting additional air from somewhere, that's why you have to use the choke circuit to close off air and add fuel. I would look at the throttle shafts and bores, and also the carburetor to manifold gasket.