cub running rich

Wed May 22, 2013 7:33 pm

my 48 cub is smoking black and running poorly, no power. the plugs turn black quickly and the carburater gets cold and sweats. anyone know of a fix for this. the carb is new and adjusted to specs.

Re: cub running rich

Wed May 22, 2013 7:52 pm

jimclark wrote:anyone know of a fix for this.
Not yet.

Start with compression tests, dry then wet - post results. Then valve tappet adjustment - basically you need a complete tune up. May need a complete engine over haul. What is the history on this engine?

Carburetors get cold and sweat in high humidity, venturi cooling effect.

Re: cub running rich

Wed May 22, 2013 8:07 pm

compression was good but i only did it dry. i did a tuneup but no valve tappet adjustment. that is next along with a petronex ign. this was my dads tractor. he ran it hard and put it away wet for 40 years. now my owning a lifetime of memories has become a real challange.

Re: cub running rich

Wed May 22, 2013 9:38 pm

Hole in main jet to large. Had to put smaller jet in mine about 10 years ago. Loosen plug on manifold, crank tractor, replace plug with finger, play with fuel/air mix to see if it runs better. IH carbs had 4 different jets over the years. I had to drop down to next to largest. Hope this helps.

Re: cub running rich

Wed May 22, 2013 9:43 pm

BTW, hope you didn't trash the old carb it has core value, or can be repaired to like new.

Re: cub running rich

Wed May 22, 2013 10:38 pm

jimclark wrote:compression was good but i only did it dry.
In numismatic terms, good, is one step above poor (junk) rating. So, not sure what good compression means. Provide dry then wet readings.

Determine engine's mechanical condition first.

Petronex ignition system won't solve mechanical problems such as stuck or worn out rings.

If compression readings are in the 100 to 105 range dry, try Seafoam in the fuel and engine oil to free up stuck rings.

Re: cub running rich

Thu May 23, 2013 8:55 am

Take the breather pipe going to the air cleaner off at the carb and see if that makes a difference. The inside of the air cleaner may be plugged.

Re: cub running rich

Thu May 23, 2013 11:14 am

Are you positive your float is adjusted properly?

Re: cub running rich

Thu May 23, 2013 7:49 pm

thanks for the replys. i did the seafoam. cyl. comp.were between 107 and 116. i also went over the new carb. to make sure it was to spec. air filter was cleaned i an hoping the hotter spark of the petronex would help burn the excess fuel. i will look into the jet size.

Re: cub running rich

Thu May 23, 2013 8:11 pm

If you try the finger on the manifold trick and more air smooths it out then its a jet or float problem. Get it running fine on original ignition before adding something else to the mix. Original or 12v? JMHO, would not put Pertronic on 6v + gnd.

Re: cub running rich

Thu May 23, 2013 8:46 pm

jimclark wrote:i will look into the jet size.
http://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=10786&hilit=sewing+needle*

Previous post on measuring orifice size.

Re: cub running rich

Fri May 24, 2013 5:21 am

Main jet hole to big, the one that goes in the side of the carb. Many from the old school used small drill bits to clean the holes and they became enlarged. Try the different jet as danovercash states.

Re: cub running rich

Fri May 24, 2013 7:28 am

Drill bits can be helpful, just don't use them for cleaning. Number size bits can be used for checking jet size (shank end),also to resize after soldering/brazing old jet shut. Carl K. Has the orifice sizes, maybe he will post?

Re: cub running rich

Fri May 24, 2013 8:52 am

Which carburetor did you purchase and it's source?

Fuel dripping out of the carburetor weep hole or throat? If the carburetor is not dripping fuel - it's probably not the fault.

My next step would be to finish the tune up, valve tappet adjustment. Then triple check the ignition system: timing, spark to each plug, plug wires on correct spark plug. Ignition fault(s) will cause the symptoms initially described.

Re: cub running rich

Fri May 24, 2013 4:04 pm

jimclark wrote:my 48 cub is smoking black and running poorly, no power. the plugs turn black quickly and the carbureter gets cold and sweats. anyone know of a fix for this. the carb is new and adjusted to specs.

http://www.ehow.com/list_7443696_igniti ... ptoms.html