Sym DD 50 won't start or dies out quick.

I have a Sym Dd 50. Was stood for 4 months. Battery dead. Worked off kick start. Increasingly kick start not getting the bike started. Kick start mechanism fine.

I connected the battery to car battery to jump start. Mostly electric start just turns bike over but does t start it. I checked the spark from the spark plug that's fine. When I take the spark plug out it's black at the end, wet and smells of petrol.

Sometimes the bike will start with a jump but only stay running for 10 seconds or so then just dies out.

Any ideas? Below is a photo of the spark plug 1 hour after having been stood. It had started with a jump for about 15 seconds then died out.

It's a 2 stroke moped.

 

Is that a peice of piston on the end of the spark plug?

 

Hi no I took the spark plug to a shop to buy a new one and the guy said its soot?!

Well a slight update. I don't know what it's called but my son cleaned out the part of engine that spark plug goes in. Also cleaned the spark plug and then jumped it again. The bike worked for a good 4 hours. Electric start and everything. Good acceleration. No probs. But just now won't start again but it does seem like there is an issue with the fuel and oil mixture as quite a bit of smoke out of exhaust and a bit of oil around air filter pipe where it connects to the carburetor. Back to cleaning it and seeing what happens.

 

New battery. They don't like being sat months on end unused unless brand new.

 

Beg, borrow or buy a compression tester and read the cylinder compression. Should be at least 100psi to 120psi.
Leave the tester attached and see if the presssure drops over about half an hour.
Maybe it's due for at least new rings, or maybe a piston kit.
Not expensive by any means. Piston kit about £30 absolute tops for a Meteor piston plus gaskets about a tenner.

 

It is now resolved. I don't know why this worked but my son cleaned out the part of engine where the spark plug sits then we adjusted the idle and air/fuel mixture. It took riding the bike up and down the street 8 or 9 times until it was tweaked perfect. Now works fine!