My Craftsman riding mower model #917-287210 is possessed. The carb floods the motor to the point it fills the cylinder even when sitting. I tried to start it for the first time this year and the engine wouldn't crank. It was like the battery was dead.

It would try to turn over but hit a point and stop. I pulled the plug to check for fire and when I cranked the motor raw gas by the ton came out the cylinder. I put the plug back in and tried to start it, it did start but I could tell it was way too rich, not running well and occasionally smoking. It died and checked the plug and it was very wet. Cranked the motor again with the plug out and more raw gas came out the cylinder and the air filter, I had removed. WTH

There is an electrical connection on the bottom of the carb bowl, is that a solenoid of some kind and could it be stuck somehow causing the carb to flood the motor? I don't think it has a fuel pump, it is a 21 HP B/S motor, I think. I know it's not a Kohler like my other mower. I guess I will pull the carb and see if the float valve, if there is one, is stuck. The owners manual and Sears parts diagram don't list the carb so I'm guessing in the dark. I did notice the oil was very thin when I changed it also so my guess is gas got the oil somehow. Any help would be appreciated. Sorry for the lengthy first post

 

It happens a lot.

Your problem is in the carburetor float valve not seating and allowing fuel to flood the engine combustion chamber and the crankcase. You'll have to fix that "leak" before doing anything. Pull off the carburetor bowl (the piece the solenoid with the wire attached) and work with the float and float valve to get it to seat with a light pressure up on the float. Check to make sure the float isn't full of gas - shake it by your ear and listen for any sloshing.

The seat for the valve may just need cleaning. You can do that with a Q-Tip with a little Comet cleaner. Then clean off the seat completely, check the valve for damage or wear and reassemble. With the carb back together and working, drain all the oil from the crankcase and blow the gas out of the combustion chamber (make sure to tie the plug wire back to prevent a spark arcing).

Then put in the new oil and you should be ready to go.

 

Comet cleaner?
Pull the whole carberater take it apart and clean it with carberator cleaner.
Very common problum. The needle valve is sticking in the float.

 

Comet cleaner on the end of a Q-Tip to clean the seat of the float valve. That may be all it needs.

 

Using anything with a grit is a poor idea.
Carburetor cleaner leaves no film or grit behind.
Last thing you want is a grit still holding the float open.

 

That's why you clean it off. Without something to smooth and polish the seat all you do is clean a rough surface.. Comet is a very light grade grit that smooths brass very well and is easy to clean off.

Carb cleaner will take out varnish but does nothing to a rough surface to smooth it.

 

Don't just indiscriminately go to town with carb cleaner. There are some seals that can not take carb cleaner and will melt. I believe they are the white neoprene seals and seats not the rubber o-rings. Not an expert, just found out the hard way.

 

Thanks guys, I'll take the carb off and see what happens. I'll let you know what I find. I thought someone must have had a problem like this before. I never had a carb with a solenoid so it's all new to me.

 

That solenoid is a fuel shutoff to help prevent the backfire after shutoff. If your carb is flooding, that solenoid isn't the problem. The problem is in the float/float valve.

 

Marbobj is correct, follow his advice and you'll get it fixed. Carb cleaner can cut the crud that my be causing the problem, but a fine abrasive works well to remove the corrosion that occurs on the brass seat and make it clean shiny brass again. I don't know which engine you have, or which carb is on it, but if you have a nikki with the plastic insert in the bowl, then it won't have a brass seat. On that carb, the problem you're having is usually caused by a bad o-ring at the top of the plastic body and the fuel inlet in the carb casting.

 

This is the first carb I've seen that had a plastic seat for the needle. I cleaned the seat and needle with a q tip and carb cleaner, put it back together now the darn thing won't run unless I squirt gas into the breather tube. It runs good with no smoke so I know it's getting fuel to the carb but not through the carb and it looks like it is leaking fuel again through a tube on the side of the carb.. but the good news is no gas in the oil. I drained the oil, put more oil in, turned it over some then drained it again to get any residue fuel out then filled with oil and and new a filter.

If the O ring is bad on top of the plastic insert above the bowl where can I find one? Is the O ring in question one of the small ones? Craftsman didn't show any repair parts for this carb in their diagram for this model. Is their a kit to rebuild this carb? Sounds to me that is what I need.

Thanks for your help guys, I was at a loss....

 

Take the plastic inser out and look at the top of it where the needle goes. There is a small o-ring there. Go to an auto parts store and pick up a replacement that size and put it back on.