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Al

Comment to Mad Mikes kt post

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Al
I have tried to post a comment to the above post and after about a minute get a message. Waiting on reply from Simple Tractors and I can't get any further. This is what I was going to say. HI, The backfire problem is more correctly called afterfire. It is also called BSS (Brown Seat Syndrome). The problem is caused when the ignition is shut off and there is no spark. The engine winds down and the carb still feeds gas that passes through the engine unburned and enters the muffler which often is red hot, or has parts that are red hot. The gas vaporizes until the mixture reaches a level that will burn and the hot metal ignites it and bang out the muffler. The best fix is to let it idle for 30 to 60 seconds and have the carb idle stop backed out to reduce the idle speed slightly below spec. This cools the muffler down and reduces the wind down and the amount of gas reaching the muffler. NEW GENERATION ENGINES: EXACT OPPOSITE!! These engines have a solenoid on the carb. that shuts off the fuel at the main jet of the carb when the switch is turned off. IF they are shut off at idle, the idle circuit still feeds gas and still bangs. THESE ENGINES ARE DESIGNED TO BE SHUT OFF AT 3/4 TO FULL THROTTLE! When this is done the governor holds the carb throttle plate wide open as soon as the switch is shut off and the RPM starts to drop. The governor is opening the carb to get the speed back up. Since the throttle plate is held wide open, the solenoid has shut off the main jet, and in this mode no gas is provided through the idle circuit. There is no gas to the engine in wind down. With only air going through the engine and into the muffler. The muffler is cooled and there is no fuel to explode. Please the engine owners manuals on any of the newer engines with fuel solenoids. THEY ALL say to shut off with the throttle 3/4 or higher. Why would they put in a 60 to 100 dollar solenoid if they didn't tell you how to benefit from it. Al Eden

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Burntime
I can tell you my kt will backfire unless idled down or choked to death. I have had 3 in good shape and they are all identical. Shutting down at higher rpms has not helped the 3 I have had...mileage may vary!:D

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Al
Hi, The solenoids are not used on the KTs. They are used on the newer families of engines. They were developed because the mfrs. couldn't come up with an easier solution to the after fire problem. Engines without the solenoids only hope is a slow idle cool down for a minute or so and then often times that doesn't work. New generation engines with solenoids don't after fire if the wide open shut down instructions are followed. To stop after fire is their only function and sorry Roy they are 60 to 100 dollars. If they get sticky, they can often be cleaned up and freed with spray carb cleaner. If they go bad and you don't want to spend the money for a new one, you can grind the end of the plunger that seats in the main jet off and the engine will work absolutely normal. When you shut it down it will after fire like the old engines did and you will want to shut it down at idle. With the solenoid working it will also after fire like the old engines if you shut it down at idle instead of wide open. Al Eden

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