(800) 853-2651
SHOP NOW

Vacuum leak

C

Craig45

Member
Working on a " new " F 12, runs well at idle but the higher the rpm the rougher it runs. How do you tell if there is a vacuum leak? Timing is right on, valves adjusted, carb seems to be about right, no smoke. Thanks Craig
 
Possible that the mag isn't advancing as RPM's increase. Someone else on here will know about getting the advance set up properly.
 
I think the mag has only impulse at TDC, and Full advance, nothing imbetween. If itital timing is good at Impulse trigger, it is as good as it gets. Unless it has a hand advance system Sone early IHC did. Jim
 
A mag that is not delivering enough at higher speeds might be the cause, another is insufficient fuel flow, or high speed circuit partially plugged or not rich enough if adjustable. Jim
 
If you let it continue to run in the higher rpms, what happens? Does it keep running, or eventually shut off? Did you try and adjust the carb while its running at high idle? Do you have the mag at full "advance"? (That should cause a problem, but just asking) It doesnt take much of a charge on the magnet to make it run right, unless its really, really weak.
 
The mag has a manual advance and moving it to advanced position doesn't seem to make much difference. I can turn the main fuel screw counter clockwise and get it to run rich, black smoke.It has strong spark on all cylinders, spark will jump from my screw driver to the block about 1/4 inch. I didn't,t do a compression check. Thanks, Craig
 
Weak or broken valve spring/s can do it, Bad plug wires, Mag/cap/rotor can do it, Water in the fuel bowl can do it (more flow, more % of H2O.) Jim
 
Run it with the carb linkage cover off. See if the linkage from the governor is steady. Mine had a broken gov. weight. Ran smooth at idle, rough at higher speed.
 
You must log in or register to reply here.

Similar threads

D
1963 Ford 4000 Gas carburetor trouble. Any suggestions??
2
Replies
27
Views
756
DLPinnix78
D
T
Stumped on M Tuning
Replies
14
Views
637
560Dennis
560Dennis
J
Another Thing On Valve Jobs
2
Replies
37
Views
1K
nick831
N
A
Ford 861D timing
Replies
3
Views
192
used red MN
U
G
Super A governor adjustment
Replies
5
Views
292
560Dennis
560Dennis
Tractor Parts Tractor Manuals

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.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top