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James W
James W, Small Engine Troubleshooting Expert
Category: Small Engine
Satisfied Customers: 3708
Experience:  7 years as Mechanic & Parts Manager for Brother who has Owned Lawn & Garden Repair shop for 35 years
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i have a craftsman riding mower with a 17.0hp kohler engine

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i have a craftsman riding mower with a 17.0hp kohler engine that is hard to start and sounds like it is out of time. it blows gas out of the carburetor and out of the muffler. while it is running the muffler turns cherry red and backfires thru the carburetor. before it started running like it is now it was hard to start. when you turned it over the fly wheel would go to a certain point and stop like it had more compression than the starter could turn over. at this point the gas would pour out of the muffler. but once you would get passed the spot where it would stop the flywheel it would start and run fine. the last time i used it it was running fine and now it is like this.

 

As they sit, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems.

Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.

More than 70% of all of our repairs in our lawn mower business are due to this same issue. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carb. It Must be removed from the engine, cleaned very well, blown out with compressed air and reassembled using a NEW carburetor rebuild kit. ALWAYS clean the fuel tank and replace the fuel line when doing this repair or you may have to do it all over again. The inside of the fuel line disintegrates over time and these small pieces of rubber will plug up the carb too. Dirt and water from a dirty fuel tank will also plug up the carb. Find the Model, type and serial or code numbers off of the engine and take them to your local dealer to get the carb kit.

 

The float could be defective as well. It could either have a hole or small pin holes it it.

Or it could just be misadjusted.

Or there could be something stopping it from causing the needle valve to make a tight seal to shut off the gas when there is enough in the bowl.

 

In any case, you should not have gas in the muffler.

 

Worse yet, if the carb is not working properly, the gasoline will find its way into the crankcase of the engine.

It will mix with the oil and also increase how much oil / gas mixture is in the engine.

 

Too much and you can have all sorts of problems

 

The oil / gas will push past the rings into the cylinder.

It will foul the plug, and not provide enough lubrication in the cylinder. It may run, but you may do damage.

 

Check to see if you have gas in the oil.

Check your oil level.

Remove and either clean /dry off the plug or better yet replace it.

Get the carb working correctly per above.

Change the oil.

 

Yes, you could have a timing issue, but lets check this first.

 

Has it sat for a while. How long.?

Customer: replied 7 years ago.
IT SAT FOR 6 DAYS. I CLEANED THE CARB THE OTHER DAY AND RE STARTED IT, STILL RAN THE SAME. ON THE BOTTOM OF THE CARB FLOAT BOWL IS A SILINOID OF SORTS WITH A WIRE GOING TO IT THAT GOT VARY TO THE TOUCH AFTER CRANKING THE MOTOR OVER WITHOUT THE PLUG WIRE ON. IF IT IS THE TIMING HOW DO I FIND OUT?

The item you are speaking of is called a Afterfire solinoid.

It's sole purpose in life is to prevent that ONE last Backfire that happens when you shut off the engine and there is still enough heat in the cylinder to ignite the next strokes fuel.

 

It drops another needle into the carb to STOP the flow of gas..

 

It could be bad, but most likely not.

 

My answer is ..

 

Re-build the carburetor using New parts.

 

There must be a problem with the needle and seat and the way it is regulating the flow of fuel.. Or with the float in the way it causes the needle and seat to activate.

 

You MUST replace the fuel line because iin time small particles of rubber and STUFF break off of it and get loged in the carb. It will cause carb problems over and over again.

 

Also, you must completely clean out the gas tank till shiny removing ANYTHING which could be a contaminant.

 

There is either a metal needle that meets with a rubber seat.

Or there is a rubber tipped needle that mates with a brass seat.

 

This seal must be PERFECT..

 

The rubbber deteriorates.

 

The metal gets scores on it.

 

Worse yet, sometimes the brass seat is not replaceable and gets an imperfection on it that causes one to have to REPLACE the carburetor.

 

Bad Timing will NOT be what allows the flooding

 

I don't want to beat a dead horse, but cleaning is not the same as rebuilding the carb.

 

Get your money's worth and take my advice, please.

 

I called and got a 2nd opinion on this one from the boss, and he has said the same thing. Thanks...

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How can I test the solenoid on my carburetor?
Answer

The anti-after fire solenoid is a device that shuts OFF the fuel at the carburetor to prevent the engine from receiving fuel after the ignition switch is shut OFF. Anti-afterfire solenoids are installed on select engines that have a battery-powered electrical system. To test the anti-afterfire solenoid, connect one pole of a 9 V battery to the spade terminal and the other pole to the solenoid case. A sharp distinct movement should be seen. If not, the solenoid is defective. Care should be taken to prevent damage caused by over extension of the plunger during removal and installation.

When testing some anti-afterfire solenoids, the plunger must be touched or nudged to initiate movement. When installed in the carburetor, the anti-afterfire solenoid plunger contacts the orifice in the jet before reaching the maximum extended position. When removed from the carburetor, the plunger is in maximum extended position. A nudge may be required because power from the 9 V battery may not be sufficient power to retract the plunger from the maximum extended position.

This solenoid must be connected to 12 volts while the engine is running and no voltage when the key switch is turned off. It can come 2 ways. The old style had the solenoid case as the ground, which automatically grounded it when it was screwed into the carburetor and the black wire went to the key switch. Now, there are 2 wires, the gray one goes to the key switch and the black one goes to ground.