Small Engines (Lawn Mowers, etc.): still miss fire,hear pop in carb,, fuel tank cap, head bolts

Question
Hi Ben, thanks for your reply the other day, you got it running for me, I set the timeing as you said, lossen bolts on magneto, snug one set ay .015 let meg pull magneto in then tighten, turn in the screws in on carburetor then back out 1 1/2 turns, it started and speeds up and down as it should But it still keeps poping in the carburetor, any ideas ???, Thanks So Much For Your Time, God Bless

Answer
Bill
Some engines have a small popping sound when they are running,It has to do with the crappy gas we buy today. Who knows what they put in the gas alcohol which is bad for the carbs and the valves because it burns too hot and then you get that popping sound.Try switching gas at different gas stations to see if that may solve the problem. If you fill it up do not over fill the tank needs to breathe. Plus when you fill it up too much you may be giving away your child's collage money with the price they charge today. Always use regular gas.  

Problem: Engine misses or pops.
Possible causes:

  1. Spark plug is fouled, improperly gapped, or damaged.
  2. Breaker points are pitted or improperly gapped, breaker arm is sluggish, or condenser is bad.
  3. Carburetor needs adjustment or service.
  4. Fuel line, fuel filter, or fuel tank cap vent is clogged, or fuel shutoff valve partially closed.
  5. Valves not adjusted properly or valve springs weak.

if the miss is a miss, the problem probably has to do with ignition or the fuel mixture. Check the tightness of the carburetor mounting bolts and where the intake manifold/air-fuel mix tube fastens to the engine block.

If instead, the miss is popping through the exhaust, this might be caused by a bad exhaust valve or valve seat.

If there is puffing or popping near the engine head, the head bolts might not be tight.

If the engine spins over too freely when it's hot.. indicating much lower compression, check the torque of the head bolts.. if they were loose, the engine should now restart.

If it won't restart until it's cooled down, the exhaust valve (and/or valve seat) may be the problem. If you can remove and disassemble the engine yourself, this isn't expensive to have corrected. If not, the shop labor for tear-down and reassembly will be fairly costly. A common reason for exhaust valve failure is that grass clippings become embedded in the cooling fins