I have a Yiben wjm50qt-9.It is lossing power on the flat.The fuel has been changed and spark plugs. The carb was very wet and as been dryed out.

The big question is it being fouled with too much fuel or is it an excess of oil?

Excess fuel would initially cause dry soot to form on the insulator until the build-up becomes so severe the carbon begins to short out the spark and then plug wetting will occur. If there is a large amount of excess fuel plug wetting will be almost immediate but this will be obvious due to the inevitable bad running.
If removed it will tend to dry in the free air.

An excess of oil will start to wet the plug almost immediately but the plug won't dry in free air.

Possible causes of excess fuel: leaky carb float valve, carb fuel level too high, mixture maladjusted, blocked air filter...

Possible causes of excess oil: oil level too high, piston rings, valve guides, too much oil in 2-stroke mix, faulty crankcase breather...

A further possibility is the wrong heat grade of spark plug.

Hi Charles:
I'd start by checking the spark plug condition and function.
Wet........... no spark
Dry............ no fuel
Check for spark anyway. Hot and blue.
Try priming carb with a squirt of gas.
Drain and flush carb. You may need to remove and thoroughly clean if gummed up.

Hi Sandy:
Hmmmmm.
Something must have happened.
Back to basics.
Pull plugs, check for hot blue spark.
Plugs wet? Fouled?
If dry and spark then no fuel.
Drain/flush carb.
Change fuel filter.
Think of it as entertainment.
Cheers,
Happy New Year.

Is the plug wet?, maybe it's either flooded or it's not getting fuel.
Pull plug if wet dry it, make sure fuel off and crank bike with out plug in to clear the cylinder. Replace plug, try to start. if it doesn't start then you have to determine if it's flooding or if it isn't. Hows the spark look? Orange or white/blue? How fast is it cranking? Is the battery fully charged?

Fuel pump not giving enough pressure out of idle...seeing that you have changed the carb....you are having a fuel air ratio problem. Check carb again and then check your fuel pump.

First remove one or more spark plug and check if they fire during cranking ( Replace therefore the plug in the plug cap and place the metallic side of the plug against the engine-block and crank.)
If NO spark check:
- Deadman knob-is the puller installed?
- Unplug the wiring to remote-control and check spark with manual start. If you have sparks: Problem with contact key/remote control circuit ( check for worn cable, bad RPM counter )
Still no sparks: Check CDI-box
If the plugs are WET: dry them with air, or better replace them!

If you have sparks: Check if fuel come to the carbs. Therefore, unscrew the drain plug ofan upper carburettor at the side of the cowls.
If there is fuel, check after cranking if the plugs are 'wet'. If they're dry: clean the carburettors

If plugs were wet: Empty all the carb cowls ( drain plug ), remove the fuel line ( pince it with pliers if no quick connector ). Crank the engine while carbs are full open throttle for 15 seconds.
Set everything back ( plugs, fuel line, drain plugs, spark plug caps ) and give it a try...

Not much info to go by, but i'll give some things to check. Got fuel? Got Spark? Got Compression? If you have all these things, after kicking several times, pull plug to see if the plug is wet. If wet dry with compressed air, ground plug on head bolt or use spark tester, Kick engine over while watching plug, it should spark. If not replace and try again. If still no spark, check kill switch with ohm meter to make sure is working properly. If still no spark you will have an electrical issue with either the CDI Box or Stator. If the plug was dry without fuel, pull fuel line from carb. check to make sure fuel is running, if not check fuel shut off valve. sometimes the shutoff valve will clog up. If all is well it has to be a clogged carb.. Good Luck

I would suggest that you cleanyour carburetors.
To tell if they need cleaned, spray carb clean in the back of the carb and the kick it over, if it starts right up, then you need to clean your carbs., Drain your gas tank and install a new fuel filter, and put new gas in the tank too.

If it doesn't start right up on the carb cleaner, then check to see if you are getting spark.
If you have spark, then test your compression.
Compression should be at least 125-145 psi but not less than 100 psi to run.

If you don't have spark, pull power wire off coil and see if you have power to the coil.
If you do have power then your coil is bad.
if you don't have power, make sure your on/off switch is working. check wires

As long as you have good compression, good fuel and good spark, that motor will start.

Pull out the plugs and see if they are dry, or wet or , black and sooty.
If dry - no fuel
if wet - no fire or misfire
if black and sooty - clean & check gap or replace with new ones.

i have the same bike try this. Firstly check the fuel is fairly fresh, using premium fuel on this model seems to work well. drain a little fuel from each carb to remove poss water build up and get fresh fuel. if spark plugs over 6 months old or over 5000 miles change as zxrs` eat plugs a spark does not mean it is allways good. i have changed to irridium plugs and have not had problems since . before you take out plugs turn over the engine a few times then when you remove each plug they should be wet ,if one is dry no fuel so clean carb,remove plug caps before you do this and note exact location of each.good luck Bri.