Spark plug stop working

[dmpatanis]

Hello,i want to help me to find why my spark plug "NGK B7HS" that i use in 60cc 2stroke engine after 7-10hours of use sudenly stop to make spark?????
Please help me.

 

[GearNut]

Are you sure the problem is not:
The kill button
The spark plug cap
The spark plug wire
The wiring between the mag and cdi
The mag
The cdi
?

 

[dmpatanis]

The engine works fine and the kill switch.I have change the spark plug with NGK and the wire.

 

[GearNut]

So you changed out the spark plug and it runs again?
If so, it's not the first time a brand new spark plug has failed. Nothing is perfect in this world, even one of the most reliable brands of spark plug made are not immune.

 

[dmpatanis]

No when i put a new spark plug the engine runs fine for 7-10km then the spark dies.Then i replace it with new one and all was fine again.
Why??

 

[Pablo]

Sounds like the plug is fouling. Try a heat range hotter plug. Try a B6HS or B5HS.

What does the plug look like? Picture?

What oil and ratio are you running?

 

[dmpatanis]

I have got the stock carb and i use 50:1 fuel-oil ratio.
When i tryed to put 30:1 the engine didnt fire up.Only in 50:1 fires.I dont know why.

 

[GearNut]

Follow Pablo's lead. The oil ratio you are running is fine if that it what your particular oil of choice recommends. The jetting of the carburetor has a profound effect on proper combustion and spark plug fouling. The heat range of the spark plug is important too.
If it is too cold it cannot keep itself clean, if it is too hot it can do damage.
I too ask, can you share a photo of your spark plug, the sparking end of it?
It may be too cold or your carburetor is tuned too rich. The color of the combustion residue left on the spark plug will help determine the next course of action.