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Donald, Small Engine Technician
Category: Small Engine
Satisfied Customers: 2043
Experience:  I have 25+ years of experience repairing 2 & 4 cycle engines
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I have a &S 13 hp engine on a swisher mover deck. Just

Customer Question

I have a B&S 13 hp engine on a swisher mover deck. Just replaced the Walbro carb with a Niki. Ran fine at first and now is blowing black smoke, and flame at times. How can I adjust the carb since the adjustment screw has no effect
Submitted: 1 year ago.
Category: Small Engine
Expert:  Donald replied 1 year ago.
Hello. My name is***** will be happy to assist you with your question.
Expert:  Donald replied 1 year ago.

Have you checked your air filter? If not, check your air filter. Did you clean your fuel tank, and replace your fuel filter, before putting on your new carburetor?

Expert:  Donald replied 1 year ago.

Many times, black smoke indicates that your carburetor is flooding. If you did not clean your fuel tank, and replace your fuel filter, sediments from your fuel tank could be inside your new carburetor, preventing your needle from seating properly.

Customer: replied 1 year ago.
I cleaned the tank out, and have all new gas lines and gas filter. It did run fine for about 10 minutes or so why mowing. This carburetor (P/N) 692037 shows a black "idle" cap over the adjusting screw (not the idle screw). The carburetor did not come with one, and not sure what impact that would have.
I did turn the screw in all the way, and back out twice a far and still runs rough (fine for 1 sec, then pops/sputters) and has black smoke. Replaced the spark plug as well and same thing.
Expert:  Donald replied 1 year ago.

Thank you for this information. What about your air filter?

Expert:  Donald replied 1 year ago.

Check to make sure your choke is not sticking ...

Customer: replied 1 year ago.
Airfilter isn't new, but it's clean. Same issue even with the air filter off. Checked the choke and it is not sticking. Do you know if there is anything different regarding carb adjustment. There is a what I'll describe as a stud in the center of the adjustment, and the screw/spring is on the outside of that.
Expert:  Donald replied 1 year ago.
Based upon what we have covered, you may have an ignition problem. Adjustments to your Nikki carburetor, is very limited. Were you having the same problem when your Walbro carburetor was in place? I am assuming that your Nikki carburetor is brand new.
Customer: replied 1 year ago.
Was not the coil. Replaced and no change.
Customer: replied 1 year ago.
Walbro carb was junk when I received the mower. THe mower ran great for about 15 minutes then back firing.
Expert:  Donald replied 1 year ago.

Thank you for your response. There is a small black wire attached to your ignition coil. This is your kill wire. Remove this wire, and give your mower another try. Let's see if this makes any difference.