Fuel Mixture

Farmall Cub Forum -- Questions and answers to all of your Cub related issues.

Moderator: Team Cub

Forum rules
Notice: For sale and wanted posts are not allowed in this forum. Please use our free classifieds or one of our site sponsors for your tractor and parts needs.

Fuel Mixture

Postby vwfish » Tue Jun 18, 2013 7:49 pm

How can I lean out the fuel mixture on my cub?
It seems to be running rich.
Black on the tip of the stack and blows black crap all over the hood.
vwfish
Cub Star
Cub Star
 
Posts: 94
Joined: Sun Jan 06, 2013 2:56 pm
Zip Code: 53029

Re: Fuel Mixture

Postby Rudi » Tue Jun 18, 2013 8:03 pm

Check and see if the air intake is plugged or the oil bath filter. Diagnosing Engine Troubles.
Confusion breeds Discussion which breeds Knowledge which breeds Confidence which breeds Friendship

User avatar
Rudi
Team Cub
Team Cub
 
Posts: 28471
Joined: Sun Feb 02, 2003 8:37 pm
Location: NB Dieppe, Canada
Zip Code: E1A7J3
eBay ID: ve9rhs
Skype Name: R.H. "Rudi" Saueracker, SSM
Tractors Owned: 1947 Cub "Granny"
1948 Cub "Ellie-Mae"
1951 Cub "Jethro"
Dad's Putt-Putt
IH 129 CC
Circle of Safety Award
Circle of Safety: Y
Twitter ID: Rudi Saueracker, SSM

Re: Fuel Mixture

Postby vwfish » Wed Jun 19, 2013 7:16 am

Thanks for the link!
vwfish
Cub Star
Cub Star
 
Posts: 94
Joined: Sun Jan 06, 2013 2:56 pm
Zip Code: 53029

Re: Fuel Mixture

Postby Eugene » Wed Jun 19, 2013 7:39 am

vwfish wrote:How can I lean out the fuel mixture on my cub? It seems to be running rich. Black on the tip of the stack and blows black crap all over the hood.
Describe the black crap; sooty, oily, wet. Engine running fine, good power, or faultering? Check spark plug color/condition for hint to problem.

Carburetion, could be some one enlarged the main jet. That's in addition to the other potential problems listed in the link posted by Rudi.

Problem might also be mechanical. Suggest doing a compression tests, dry then wet.
I have an excuse. CRS.
Eugene
Team Cub Mentor
Team Cub Mentor
 
Posts: 12525
Joined: Fri Jul 02, 2004 9:52 pm
Location: Mo. Linn
Zip Code: 65051
Circle of Safety Award
Circle of Safety: Y

Re: Fuel Mixture

Postby John *.?-!.* cub owner » Wed Jun 19, 2013 9:06 am

Most engines leave a black coating in the exhaust pipe (soot) unless they are really worked hard for long periods. The jets are preset for handling a load, which requires a richer mixture than just piddling around. The spots on the hood are probably droplets of water from condensation in the exhaust as it warms up when first started carrying specs of carbon with them.
"The Constitution is not an instrument for the government
to restrain the people, it is an instrument for the people to restrain the
government lest it come to dominate our lives and interests." Patrick Henry
User avatar
John *.?-!.* cub owner
Team Cub Guide
Team Cub Guide
 
Posts: 19474
Joined: Sun Feb 02, 2003 2:09 pm
Location: Mo, Potosi
Zip Code: 63664
Tractors Owned: 47, 48, 49 cub plus Wagner loader & other attachments. 41 Farmall H.

Re: Fuel Mixture

Postby Matt Kirsch » Wed Jun 19, 2013 10:05 am

Yes, in a nutshell there is no fuel mixture adjustment on a Cub carburetor.

About the only thing that could be causing an overly-rich condition is the float being set too high.
Matt Kirsch
10+ Years
10+ Years
 
Posts: 3357
Joined: Tue Jun 08, 2004 3:04 pm
Location: Rochester, NY
Zip Code: 14559
Circle of Safety Award
Circle of Safety: Y

Re: Fuel Mixture

Postby vwfish » Sun Jun 30, 2013 2:53 pm

I adjusted the idle screw and throttle stop per the operators manual and it seems to be running much better.
Looks like the PO backed the throttle stop all the way out and just used the idle screw to adjust (it was backed out about 5-6 turns).
The manual says to turn the idle screw all the way in, back it out one turn, set the throttles stop for desired idle speed and adjust the idle screw out 1/2 to 1 turns for smooth running.
vwfish
Cub Star
Cub Star
 
Posts: 94
Joined: Sun Jan 06, 2013 2:56 pm
Zip Code: 53029

Re: Fuel Mixture

Postby danovercash » Sun Jun 30, 2013 3:37 pm

What John said, plus the IH carb had 4 jet/Venturi tube combinations. Remove plug in manifold above carb and replace with your finger to play with fuel/air mix. If adding more air makes it run better/smoother then you need a smaller jet.
"It is impossible for a man to learn what he thinks he already knows." -Epictetus

252646 & 221525. 195897 (Gone but not forgotten!)
http://groups.yahoo.com/group/dansfarmallcub/
danovercash
10+ Years
10+ Years
 
Posts: 2891
Joined: Mon Feb 17, 2003 8:48 pm
Location: NC, Kannapolis
Zip Code: 28081
Circle of Safety Award
Circle of Safety: Y


Return to Farmall Cub

Who is online

Users browsing this forum: ad356, Stanton and 8 guests