Cylinder compression Can't start due to compression built-up. Can't spind the engine over fast enought. Take spark plug out and engine spind freely.

Every internal combustion engine needs compression, fuel, air and spark. If any of these are missing, the engine will misfire. Lack of compression can be due to head gasket failure, burnt valves or worn compression rings. Rings are the most unlikely if only one cylinder is misfiring. Lack of compression can be measured with a fairly inexpensive pressure gauge from the local auto parts shop. The cause of lack of compression (head gasket, burnt valves) will be a more serious matter.

Compression is measured by removing the spark plug of the suspected misfiring cylinder and inserting the pressure gauge firmly into the plug opening while an assistant (your wife or sweetheart will do fine) turns the key to swing the engine. Compare the reading with a known good cylinder. The readings should have at most not more than a 5% variance.

If the compression is good, start with the spark. Do not be fooled by a "nice"spark coming from the plug lead. Swap plug wires with a known good cylinder and see if the problem moves. Check the distributor cap for cracks, which also are sometimes next to impossible to see with the naked eye, so if an exchange cap is available, try swapping. The final, but most unlikely culprit is the spark plug itself. If it is not new, fit new plugs, they\'re cheap enough.

Then, a sly little monster that has caught me a time or two is the distributor cam. In an older vehicle the distributor cam can have a worn bush, which will open the points when the cam is on one end of its travel, while barely or not at all open the points when it is opposite, thereby causing a weak or even absent spark to the cylinder it is supposed to ignite at that end.

Since the other cylinders appear to be firing OK, the problem is not with air supply (unless of course the air intake inside the manifold is blocked by a rag someone had forgotten to take out while they were cleaning the engine, but let\'s not go there.)

Check you have a spark, connect a spare plug and hold it to an earth, crank the engine and watch for a spark. If not check your ignition circuit. If a good strong spark proceed:
Check fuel supply to carburettor - make sure there are no transit plugs that have not been removed. Easiest way is to disconnect the supply hose - no naked lights!!!!
If that\'s OK remove the carburettor float chamber and check that fuel is reaching the carburettor. If the float chamber is dry, check the float valve assembly. There\'s not usually much to small engine carburettors so if the fuels getting to the carb it may be a blocked jet or just very badly adjusted. There is also the possibility that the carb is faulty (yes I know it\'s new but ...!).
If fuel and spark is OK then it could be the spark timing - it should be OK unless you\'ve stripped the engine. On some engine\'s it is possible to set the spark 180 degrees out so that it sparks on the exhaust stroke - just to confuse things some engines spark on both exhaust & compression.
Good Luck!

engine miss caused by many things,weak ignition from bad ignition coil, ignition timing off if you have high mileage engine low compression from worn burned valves.could have something minor like stopped up air filter, clogged dirty fuel injectors, through the years i have seen many things cause engine to miss.

I would have installed new spark plugs,all new coils
& mailed away the injectors to be ultra sonic cleaned
while the motor was out.

I wouldn't do compression,do cylinder leak down test
before, you ever install any motor, to check it's mechanical
condition

Replace front or upstream O2 Sensors, as I assume they
have over 100,000 miles on them

Check fuel pressure & use professional scan tool software
to look at ALL data

It takes 3 things for an internal combustion engine to run... compression, spark, and fuel.
First perform a compression test. If its under 90psi the compression is too low and it would cost more to repair than to replace.
Sidenote: A unit that is extremely flooded will give a false low compression reading. Remove the spark plug, turn unit upside down so that spark plug hole is facing down and slowly pull the starter rope. If fuel drips out then the crankcase is flooded with fuel.
Next, be sure that your fuel is fresh and free of water. If the fuel is more than 20 days old it is stale.
Also, holding the spark plug against the head is not an accurate test for spark. A failed spark plug or weak module will fire when not under a load but will not fire when in the cylinder environment under compression. A spark tester is the best way to know for sure that you have a good strong spark.
Lastly, something you can do which requires no special tools is check the condition of the cylinder/ piston. Remove the spark plug then remove the muffler and look into the cylinder. You can pull the starter rope slowly to move the piston up and down. Observe the wall of the cylinder and the side of the piston. They should be smooth and shiny. A dull grey appearence indicates debris ingestion, grooves ( also called scoring) indicate metal to metal contact caused by a break down of the oil due to heat or lack of oil. The presence of scoring means that the unit is not cost effective to repair and should be replaced. Dull grey usually means low compression too.

Check or replace ignition wire, spark plug spark plug coil. Run a cylinder compression check. Should have same compression on both cylinders. If not, burnt valve, or flat cam lobe.

Electronic ignition units work off speed of rotation so make sure yoy are cranking the engine fast enough, make sure the plug is well earthed against the cylinder whilst cranking, make sure the switch is in the on position, if there is still no spark you will have to replace the unit.

The timinmg is preset by the permanent keyed slot built into the inside of the flywheel where it mates with the crankshaft. If the key was broken off, you would get No spark because of the nature of the magneto ignition. Your compression is actually pretty low for a 2 stroke. It should run higher like around 90+. Try this. With plug removed, cover plug hole with thumb and give the pull start a real strong pull. It should push your thumb off of the hole. If it doesn't the compression is too low for the engine to run. Scored piston walls, or cylinder walls could be the problem. Again 60PSI is really low. I would remove the jug and check for piston scoring and cylinder scoring. The engine can be easily rebuilt (but not real cost effective).

P0301 - Cylinder 1 Misfire Detected.

Causes:
- Improper spark plug at cylinder #1
- Insufficient compression at cylinder #1
- Incorrect fuel pressure
- The injector circuit is open or shorted at cylinder #1
- Fuel injector #1 may be faulty
- Intake air leak

Solutions:
- Perform Injector Service
- Replaced Spark Plug #1
- Replaced Injector #1
- Replaced Ignition Coil #1

P0303 - Cylinder 3 Misfire Detected.
Follow info from P0301.

P0316 - Misfire Occurred In The First 1,000 Engine Revolutions.

Causes:
- Damaged CKP sensor.
- Ignition System.
- Fuel Injectors
- Running out of fuel
- Fuel Quality
- Base engine
- Damaged Powertrain Control Module

Solutions:
Usually the P0316 is combine with a P03XX codes. The P03XX code indicates in which cylinder the misfire occurred.

How to Test Engine CompressionAn engine depends on an equal compression reading in each cylinder to run smoothly. If poor compression exits in one or more cylinders it can cause a rough idle condition and low power. A compression test can be performed to check wear or internal damage. To start a engine compression test gauge is needed. There are two types of gauge styles, one threads into the spark plug hole which is more accurate. The other style of gauge is constructed with a rubber plug that is meant to be pressed against the spark plug hole, this style of gauge is difficult to use. To perform a engine cylinder compression test follow the steps below.

• Remove ignition coil connector or ignition system fuse to disable power to the ignition system
  
• Test ignition system to ensure that the power to the system has been disabled
  
• Remove #1 cylinder spark plug and insert compression gauge, most gauges have a hose attachment that is installed into the spark plug hole with the gauge connecting to the gauge hose.

Engine Cylinder Compression Gauge

• After the compression gauge has been inserted, use the starter to crank the engine over for about five seconds. Use about the same five seconds to test the remaining cylinders.
  
• Record the compression reading as each cylinder is tested
  
• Remove the compression gauge and reinsert the spark plug
  
• Follow this procedure until all cylinders have been tested
  
• Compare cylinders compression reading, all readings should be within about 5% of each other

If low compression exists a cylinder malfunction exits and further inspection is required. Possible causes for a low compression condition are: burned intake or exhaust valve, broken piston or piston ring, broken valve spring or a blown head gasket.