MG Car Repair: 75 mg midget wont start, piston engines, combustion chamber

Question
QUESTION: Hi there i have a 75  midget and it was running great then we put in a new battery now it wont start. it sounds like it wants too it is turning but wont turn over. any suggestions?

ANSWER: HI Olivia,
All piston engines require only three items to run, Compression, Fire and fuel with conditions on each.
compression ---- 125 to 180 PSI on a compression test
Fire ---------- A thick blue spark at the plug at about the correct time.
Fuel ----- A combustible fuel available to the combustion chamber in about the correct fuel/air ratio.
One or more of these three items are missing if the engine does not start.
Compression will not go away just installing a battery so examine fire and fuel.
Let me know,
Howard

---------- FOLLOW-UP ----------

QUESTION: Hi and thank you. ok lets start at 1 i dont know much about engines so what do i need to do to get this so i understand it. is there anything with a print out to show a abc of how to go about this? is there somthing i need to buy to test all of this?

Answer
You can do a rough check for spark by removing a spark plug and place the plug on the wire and lay it on a metal part of the engine. Then put your thumb over the plug hole and have someone spin the starter.
The compression will cause your thumb to make a "Pop" noise as it blows you thumb off of the hole. At the same time look at the spark plug and you should see a thick (pensile lead thick) blue in color (not in the sun light) spark.
If the spark is at or close to the correct timing, it will seem as though the "Pop" is causing the spark which makes a "Click" sound. If you hear and see a "Click-Pop" or a "Pop-Click" the timing is off enough to possibly cause the engine not to start. If the spark is a thin (thread size) and colored yellow or orange, the spark is weak and possibly the cause.
As for fuel you can either purchase a spray can of starting fluid or WD-40 works by spraying in the intake when someone tries to start the engine. If it starts for just a few seconds, then you have a fuel problem and need to test fuel pressure between the fuel pump and the carburetor with a fuel pressure gauge.
These are standard preliminary tests for an engine that does not start.
You shouldn't have to do a compression test because all you did was install a battery.
Let me know,
Howard