VAC Carb Issues

connor9988

Well-known Member
Location
Central Iowa
I have been working with my VAC carb for some time now trying to get it to run right again. I
have taken it apart and cleaned it several times but it still has not helped much. It starts hard
if you let it set a few hours and will sputter and cough blue smoke while surging on startup.
Then it will settle down and lose most of the blue smoke. Well today after another cleaning I was
trying to get it set right so it wouldn't sputter and surge which it was doing while running. I
eventually got it somewhat dialed in but that was with the needle screw approximately two turns
out and the idle screw all the way in (as in bottomed out).

I mounted the big blade to smooth some dirt at my brother's place and it was particularly
frustrating having to dismount and repeatedly adjust both screws to get synchronized.

Does it sound like I have air leaking in somewhere or is something else amiss?



Thank you for the help!
a272346.jpg

a272347.jpg

a272349.jpg
 
I want that blade. But yes it sounds like you're running dead lean, and maybe the needle & seat leaking while you're not running to boot. What did the carb bowl gasket look like? If not perfect I'd start there. Take a can of spray brake cleaner, carb cleaner, ether, even a pump oiler full of gasoline, squirt it at seams, gaskets, seals, anywhere from the carb to the intake ports, while it's running. When you get a large increase in RPM you found it. But don't assume there's just one problem!
 


It does sound like it's sucking in air from someplace. Did you install a new throttle shaft when you first overhauled the carburetor? A worn shaft will let a lot of air in the system and make it impossible to adjust the idle mixture. The intake manifold will be the next place to look for air leaks.
 
Conner. Not trying to be picky, but where is your SMV sign? I won't get on the highway without one.
Huge fine for you if some idiot hits you.
Richard in NW SC
 
Than you for the help and the carb PDF guys. I will grab some starting fluid and try tracking down the leak.

Richard I am one of the bad tractor owners that does not have one mounted directly to the tractor. I usually have a 3pt drawbar on the tractor that holds the SMV sign. I intend to mount the SMV
directly to the tractors but have not gotten that far yet.
 
Larry, your throttle point might have been right. No leaks around the manifold gasket but it would almost quit when I sprayed starting fluid around the throttle shaft (this was after I mostly covered the air intake to force more suction through the carb.) I installed a new throttle shaft when I restored the tractor but I am guessing that the surrounding casting has been thoroughly worn over its life.
 
(quoted from post at 20:03:15 07/04/18) Larry, your throttle point might have been right. No leaks around the manifold gasket but it would almost quit when I sprayed starting fluid around the throttle shaft (this was after I mostly covered the air intake to force more suction through the carb.) I installed a new throttle shaft when I restored the tractor but I am guessing that the surrounding casting has been thoroughly worn over its life.


What method do you use to clean your carburetor? How long ago was the new throttle shaft installed. Can you wiggle the throttle shaft on the end where the linkage hooks to it? If it's worn out at that point there will be noticeable slop around the throttle shaft. If the hole is worn, instead of the shaft, you may have to look for a different carburetor. Another option is to have the hole teamed out and press in a bronze bushing. Using a reamer, instead of a drill bit, will ensure that the hole will not be off center.
 
But you should not have had to block the air intake for that test! If under normal conditions it makes little difference, then it's not a major problem. We may be dealing with an ignition problem masked by a minor fuel problem that you'd never notice if the igniton was right. Do you have a good hot blue spark that'll jump 3/8" or better? No crack traces in the distributor cap? Points look good, set right? It also might be time to do a compression check. Fiddling with a carb or distributor on a motor with bad compression is kicking a dead horse.
 


Might also be time to check the valves. I know the last time the valves on one of my VACs was checked it was 1948... :oops:
 
(quoted from post at 19:14:11 07/06/18) Larry I will probably go the bushing route. Maybe one day I'll pony up the cash and just get a new one.

Let us know how it works out.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top