25cc TB25BP new plug, new Gas, Clean Carb.. will not start

If it has compression and spark it has to be gas. Try a new plug. If it still does not start consider replacing the carb. About $14 fro m Ebay. Make sure to replace the fuel lines going into tank. They come with a carb kit usually.

I would dump the old gas and put new gas in and see if it will start then. If not you can remove the carb and if you are careful disassemble it without damaging the gaskets spray it with carb cleaner and reassemble it and put it back on. You can also rebuild the carb if the second option doesn't work. Hope this helps.

i promise u its the carb buy the whole unit

Carb is getting gas but is the engine. Take the plug out and spray alittle starting fluid in put the plug back in and start it.

Easy way to test plug is to remove it from cylinder head, then ground its hex base to side of engine..reattatch plug wire and pull starter cord...Do this is dim light...need to see a nice blue spark. So, do that...check the plug gap and plug condition (even if new)...if it's NOT firing...try another plug...if same...you will need to pull the engine covers off and check the "air gap" of the flywheel magnets to the pickup legs on the ignition coil module. You can gap it the thickness of a regular business card (.010"-.014"). The gap has to be present for the spark plug to produce a spark.

You have most likely done this but lets go back to the basics.

Do you have spark at the plug?
Check to see if the plug is fouled - pull the plug connect to the plug wire- ground the metal part of the plug to the metal body of the engine - as you turn the engine over it should fire cleanly from the center to the electrode, if it fires off to the side or has an orange colored spark it is fouled - replace it.

Once we have spark check for gas is it getting to the carb?

90+ % of all small engines not running are due to the fuel line or in tank screen being plugged with garbage. Remove the fuel line from the carb, point it down and using a small container to catch the gas it should flow freely.
If you have good gas flow reconnect the fuel line to the carb and put about 1 CC of gas in the plug hole reinstall the plug and fire it - almost all small engines use a bit of vacuum to pull the fuel from the carb into the cylinder, jump starting them with a very small amount of gas directly in to the cylinder can help them get going.
A VERY SMALL AMOUNT OF GAS AND CLEAN UP ANY SPILLS BEFORE YOU TRY TO START !!
Burning down the house will upset the other half

The carb must be cleaned. take the carb off put it on a work bench and pull it apart layer by layer... be careful as there is a spring that will jump out. pull all of the gaskets off and clean behind them. make sure all of the passages are clean. Use brake cleaner from the auto parts store! do not use carb and choke cleaner as the gaskets will instantly expand and be useless. there is also a brass cylinder in the carb you need to remove it and clean it well. There should be a very small hole in the center. put it back together and you should be good to go

Not so many reasons she won't start. 4-Strokes are Simple!

Here they are:

Motor:
Fuel Tank-> Fuel Line-> Fuel Filter-> Carb-> Intake (Valve)-> Piston-> Exhaust (Valve)-> Muffler

Carb (Old Style):
Fuel Side:
Fuel Bowl-> Float-> Needle Seat-> Fuel Ports (Venturi)
Air Side:
Air Filter-> Carb Air Intake-> Butterflies (2)
(Clean 'em ALL!)

Hardware (Motor):
Rotor (Magnets)-> Magneto (Ignition Coil)-> Spark Plug Wire-> Spark Plug-> Cylinder Head (Spark Plug Ground)

Ignition:
Kill Switches (Seat, Clutch, etc.)-> Spark Plug/Ignition Coil-> Ground
Key Ignition-> Battery->Starter/Generator

If one of those fail.......= Non-Starting 4-Stroke!

Fixes-
Fuel:
You are either getting too much, or too little. Too much = Carb.
Too little = Carb. Therefore, tear down the Carb (COMPLETELY-Careful!) and clean it up.

Electrical:
Grounding out the System (Kill Switches)
Battery-> Ignition-> Starter.
Magneto->Plug Wire->Plug (Check 'em all!)

Take off the air cleaner and squirt gas in the carb. If it fires it is not getting gas from the tank. If it does not fire pull the spark plug and squirt a little gas in the cylinder. Replace the plug and try starting it. If it fires it is not getting gas from the carb.

try removing the muffler and scraping out any carbon build up in the exhaust mouth of the block. if that doesnt help you will probably need to replace the carb.