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Starts back firing and won’t rev-up, puffing black exhaust . I’ve cleaned carb. Disconnected coil diodes , gaped coils, checked valves.ect. The weird thing is when I move the ignition key to the off position it runs fine. But there’s no PTO ,not charging the battery ect. So what could it be ??? What’s getting turned off??

I suspect that the float valve is not sealing allowing overfilling of the carb. When you turn off the key it is killing the fuel solenoid on the carb preventing extra fuel from being drawn into the main jet of the carb. or the main jets fell out when you took the carb apart.

item 117 or 117a in this diagram https://www.partstree.com/models/44...-engine/carburetor-kit-carburetor-overhaul-3/

ILENGINE said:

I suspect that the float valve is not sealing allowing overfilling of the carb. When you turn off the key it is killing the fuel solenoid on the carb preventing extra fuel from being drawn into the main jet of the carb. or the main jets fell out when you took the carb apart.

item 117 or 117a in this diagram https://www.partstree.com/models/44...-engine/carburetor-kit-carburetor-overhaul-3/

Click to expand...

The carbs coming off tomorrow .thanks for your advice.

Hi suppraman,

I concur with the float and needle/seat being suspect.

I unplugged the fuel shutoff solenoid and it’s running better than its ever run. I know that’s only a temporary fix. The more I think about it , I believe there were no jets in the carbs. Somebody took them out for some reason. Or they fell out. Don’t jets screw into the carb ?

suppraman said:

I unplugged the fuel shutoff solenoid and it’s running better than its ever run. I know that’s only a temporary fix. The more I think about it , I believe there were no jets in the carbs. Somebody took them out for some reason. Or they fell out. Don’t jets screwIf the into the carb ?

Click to expand...

It appears you have the Nikki carb which the jets inserted from the top of bolt in emulsion tube by both the tiny O ring that is on the jet and also the diffuser tubes that are attached to the carb and slide down inside of the emulsion tube. If the emulsion tube is unbolted and removed and it turned upside down the jets do and will fall out in some cases.

suppraman said:

I unplugged the fuel shutoff solenoid and it’s running better than its ever run. I know that’s only a temporary fix. The more I think about it , I believe there were no jets in the carbs. Somebody took them out for some reason. Or they fell out. Don’t jets screw into the carb ?

Click to expand...

Hi suppraman,

Normally that solenoid has the shutoff pintle retracted when power is applied with the key on. Power turned off, the pintle extends to block fuel flow and prevent run-on backfires.

In that case, the tiny jets have fell out and were not noticed. This likely has the Nikki carburetor on it with the plastic insert in the bottom.

The other possibility is the single O-ring at the bottom of the plastic tube to seal it to the fuel bowl has cracked and come apart due to Ethanol fuel mix.

The easiest thing to do is get a complete (clone) carburetor online through Amazon or Ebay but be careful that it matches the linkage well. Some ads say they will "fit", but they are often different, especially for the choke lever connection.

An exact fit carburetor can usually be found through Parts Tree, Jacks small engine or Pro parts direct.

I want to thank everybody that responded to my questions on my mower. When I get it fixed I’ll let you guys know. I’m going to yank that carb today.