Crunning poorly at full throttle
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=18367
Printed Date: 06 Feb 2025 at 10:17pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Crunning poorly at full throttle
Posted By: craigreavley
Subject: Crunning poorly at full throttle
Date Posted: 17 Sep 2010 at 11:42am
|
My C has started sputtering randomly at full throttle. Plenty of gas to carb, carb cleaned inside, new condensor, new 303 plugs, good wires, good cap, good rotor, good points, What am I missing here. Would the 303 Autolite plugs cause an issue.
|
Replies:
Posted By: Brian Jasper co. Ia
Date Posted: 17 Sep 2010 at 11:54am
Pulling the choke a little doesn't help? If it does, there's a restriction in the carb, main needle not adjusted correctly, or a vacuum leak. Did you set the timing? Changing the points will change the timing. Overly advanced timing will make it sputter at rated speed. Is the distributor shaft wobbly in the bushings? The points cannot be properly set if the distributor shaft bushing is worn.
-------------
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
|
Posted By: craigreavley
Date Posted: 17 Sep 2010 at 11:58am
|
Pulling the choke doesnt help. What is the adjustment on the main needle. It is a marvel schebler card, and the only srew to adjust is 2 turns off bottom.I adjusted the timing and it seems to be in the middle of running poorly both directions. Distributor seems tight. What is the gap for the points, and plugs?
|
Posted By: Brian Jasper co. Ia
Date Posted: 17 Sep 2010 at 12:05pm
Not all carbs for the C had an adjustable main needle. Points are set at .020 and plugs .030 if I remember correctly. Another discussion a while back was new doesn't necessarily mean good. If you still have the old condenser, put it back in and see what happens. There could also be an internal leak in your carb. I have a similar carb on an Oliver 60 and it can be set to idle ok, or run ok above 1/2 throttle, but not both. I keep thinking I'll send it off to Steve in NJ to straighten out, but haven't gotten a "rountuit" yet...
-------------
"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
|
Posted By: Gerald J.
Date Posted: 17 Sep 2010 at 12:14pm
If choking doesn't help and there's no distributor problem, it running too rich. That should show as a black soot in the exhaust pipe, maybe some black smoke. Turn the adjustment screw and see what effect it has. These carbs were not preset and require adjustment to run well. The manual's setting is just close enough the engine will run so you can refine the setting. This is what tuning a vintage engine is. You get to trade off power for economy. Rich for most power, lean for best economy.
Gerald J.
|
Posted By: craigreavley
Date Posted: 17 Sep 2010 at 12:15pm
|
I have a much smaller zenith carb that is off of a 38B. It is half the size of the MS carb. I may try it to see if it changes the way it runs. I just ordered the main carb gasket from Sandy Lake. The zenith had a bad gasket.
|
Posted By: craigreavley
Date Posted: 17 Sep 2010 at 1:59pm
|
Gerald you are exactly right. There is black soot all over the exhaust, and I changed the plugs b/c they were fouled with black soot. It is running way too rich. It doesnt seem like turning the one screw on the carb does anything unless you turn it all the way in then the engine struggles. If i turn it all the way out it just runs the same. Why else would it run soo rich?.This has to be a carb issue right?????
|
Posted By: Gerald J.
Date Posted: 17 Sep 2010 at 6:02pm
So there's not two screws, one for idle air and one for high speed run? Sounds like there might be the wrong high speed jet or none at all. I had that happen in a VW I rebuilt long ago for a friend. Didn't perform well and used lots of gas. Lots of new engine parts didn't change it. VW mechanic finally decided to check for a main jet and it was missing.
The idle screw only adjusts decently at very slow speeds.
The governor HIDEs adjustment effects. You have to override the governor or use it as an indicator. With the governor held off, you adjust for the fastest engine speed. If you can't hold off the governor, then you need to watch the throttle shaft or segment and adjust the mixture for the minimum throttle opening. That's the governor hiding the effects of your adustment.
Gerald J.
|
Posted By: Gary in da UP
Date Posted: 17 Sep 2010 at 7:20pm
|
It sounds as if you have done everything but adjust valve lash.......
|
Posted By: jraymer2244
Date Posted: 18 Sep 2010 at 6:40am
|
I had one running like that did everything you have done still didnt fix. Finally checked the air breather tube , dirt dobbers had the air choked almost off. You might check that if you havent allready.
|
Posted By: Dave(inMA)
Date Posted: 18 Sep 2010 at 9:36am
Agree with last post - had similar problem on my WC and found the air cleaner plugged with dirt between inner and outer walls. Cleaned it and my rich running problem went away.
-------------
WC, CA, D14, WD45
|
Posted By: Gerald J.
Date Posted: 18 Sep 2010 at 11:39am
So true that the mixture depends on the air flow cleanliness before the carburetor. Bugs and birds like to nest in intake pipes and air cleaners. On my gas 4020 the Donaldson precleaner top was domed down contributing to it running rich.
One other cause of air flow restriiction can be accumulated grunge in the mesh of the vintage oil bath aircleaner. I recall many a time on this forum when part of the restoration involved burning that mesh to get rid of the accumulated grunge that limited air flow. I don't know that's good for the assembly, but its hard to clean.
Gerald J.
|
|