Kohler k321as engine- misfiring.

Question edited for clarity and spelling.
Question moved from Motorcycles category.

Guessing a sticking inlet valve or slipped timing.

https://www.google.com/search?q=lincoln+ranger+225+backfiring+engine

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Preventing Backfire on Motorcycle Exhausts ' DoItYourself ...

www.doityourself.com/.../5-tips-to-preventing-backfire-on-motorcycle-e...

When the engine on your motorcycle has an emission system malfunction, such as anexhaust leak or a moment of running rich or running lean, backfire can ...

Exhaust backfire, popping when letting off throttle - Motorcycle Forum

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Apr 26, 2009 - 28 posts - ‎17 authors
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Well to me it needs the plugs properly gapped or the motor jumped timing try the timing test and check your spark plug gapping

The point gap should be 0.013 inches. You should also check the end play and run out on the shaft before point installation (vertical & horizontal movement)- should be minimal or the engine will run erratic or not at all if too loose.

remove the top cover from the engine and then the nut on the top of the flywheel look down at the space between the shaft and flywheel the key between the two might have sheared happens more if you hit a rock

P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction,

Symptoms of a P0105 check engine light code may include:

• Poor running engine
• Engine runs rich
• Engine won't idle
• Engine backfires through tailpipe
• Engine misfire under load or at idle
• MIL (Malfunction Indicator Lamp) illumination
• In some extreme cases there may be no symptoms other than MIL illumination, could be caused by:
  • MAP sensor vacuum hose disconnected or plugged
  • Bad MAP sensor
  • Bad TPS good-day !

Timing is off,problem with timing chain,also check fluids in ******,plus also if you have a distributer in your vehicle,if it is cracked,moisture getting in and ruining the points,-that is if your vehicle has a distributer! This will make a vehicle run rough as well.
You can have new plugs put in,but if your spark plug wires are cracked or worn,this will also creat misfire and backfiring.

According to my book, the first code is the brake control rough road sensor, and P0302 is a cyllinder #2 misfire. Check the gap on your plug, and make sure the plug wire is on all the way. Give the boot an extra good push. Backfiring or misfiring under load is always caused by poor ignition. You may also have a faulty plug or wire.

points gap adjustment ,timing adjustment. carburaor set clean w/ synchronization,check for exhaust gasket leaks between cylinder head and head pipe.check valve tappet clearance adjustment.clean and oil, or replace air filter. need cylinder compression test to determine mechanical state of motor top-end

For a carbureted engine, backfires can be caused by the valve train timing being way out.
Set your timing properly first, and then move forward from there.
Blackened plugs definitely mean too rich a mixture, and maybe not enough spark to burn it all.
I've never seen a bad vacuum hose cause backfiring, but it will help very much to fix any vacuum leaks you can find.