runnin rich

[rogerk]

Hello everyone...been a long time since I have been on site not working now so has given me a chance to work on the cub again.have done all fluid changes dropped oil pan cleaned oil bath and filter.installed carb kit from Steiner did clear tube check and looks like I got the float right on the money. Problem is she seams to be running very rich..spark plugs very sooty but dry. She has good compression. 110-115. Running real gas in her. One other note air screw on carb will make it cut out if screwed in after one turn out from seated possition has no effect on idle. Fuel supply to carb is good...but that would not effect richness...or maybe I'm lookingin thewrong spot.possible weak ignition? Can weak spark look like rich running carb....sickle mowed for 3 hours yesterday ran like a champ....drove it down to the neighbors house today to Bragg!! Then she would not make it back up the hill to come home. About a20% grade had to clean plugs to get it to the house.very sooty dry plugs

[staninlowerAL]

Have you tried a higher heat range like Champion D21?

[danovercash]

Take the pipe plug out of the intake manifold and play with the air/fuel mixture to see if improves. Jet in side of card may be worn too big. Four sizes were available. Air screw is for idle only. Check archives for Lurker Carl's carb repair how to's. had to put a smaller jet in mine about ten years ago. Hope this helps.

[NJ Farmer]

Float may need adjustment or you might not have the correct or oversized main jet/discharge in the carburetor. For what ever reason you are getting too much fuel during the combustion phase of the "suck...squeeze...bang...blow.."

On the bright side at least your plugs are dry and not wet!! So I would start with a carburetor overhaul/inspection.

NJ Farmer

[rogerk]

Thanks for the replies..to add a few things I am running d_21 plugs I am starting to believe that I might have the drop set wrong on the float ..might explain why it runs good one Time then not the next..I always drain fuel at night because i keep her in the garage at night and dont want any fuel leaks etc...maybe my drop is to low and my float is getting hung up..I am using an android phone to post and cant find any way tocheck archives to reference the carlurker post can someone provide link.. or maybe my new theory is no good any input is welcome....thanks again

[danovercash]

Here you go!

http://www.cleancomputes.com/Cub/Mainte ... index.html

[rogerk]

Thanks!!!

[Rick Spivey]

I would suggest you go ahead and review the carburetor settings. However, I did want to mention that a weak magneto did cause one of our cubs to run exactly like you describe. Not sure if yours is magneto or battery ignition, if magneto, a new coil might be in order. Also you mentioned that the mixture adjust screw had no impact. It is metering air, so in would be rich, out would be lean. It should have some impact, especially on how well it runs up to high idle when you "blip" it by hand. It should run up smooth with no stumbling or hesitation. Too rich on this mixture will soot the plugs. If yours truly has no impact then the two small hole in the throat of the carb may not be open; they are hard to see, right where the butterfly hits the throat at idle. Use a small copper wire to open those up.

[NJ Farmer]

If you are getting any and I mean any fuel dripping from the carburetor when you shut down the cub you have a float issue. Also you don't have to drain all the fuel out just turn the fuel shutoff lever all the way in "clockwise" and that will shut off the gas at the tank....

Keep us posted!

NJ Farmer

[gitractorman]

On another note, most cubs run awfully rich, and it's normal, along with the black sooty plugs. Your float may need a little adjustment, but in general these engines run really rich all the time, so if it runs good under load, and you were able to mow with a sickle mower for 3 hours and thought it ran great, then you may want to stop fooling around with it.

[John *.?-!.* cub owner]

Cub engines run rich under no load or light loads, but when working hard need the higher fuel delivery. Unless you are blowing black (not blue or white) smoke, or fouling the plugs with dry black carbon (not oily), I suggest leaving it alone. All of the old IH carbs were pretty simple, and even the H and M carbs, as well as the A,B, C, all ran rich at light loads in order to have enough fuels for heavy work.