Step 1 check to see if you have a spark, Need more detail what? engine 3.5-hp clasic engine or? When did it run ok and fo how long

Thanks for the reply, sorry I am not sure about the hp, all I know that it is a 450 series B&S [model 9T502] with 148cc.

I don't have that special tool to check the spark, is there any other way you can check for spark ?

It was lent out to my brother who just told me it was puttering a bit and wouldn't rev up properly last time he used it, just before he give it back to me.

thanks for your help

"tool to check spark"
Wow I guess society is relying on gadgets a little
too much.

UNSCREW SPARK PLUG
attach plug to wire.
Rest threads securely on metal of engine.
Pull rope
LOOK at gap

I guess I got conned by a mower shop who told me I need that tool to be able to check the spark, nothing was mentioned about your suggestion, some people are dissappointing to say the least.
Anyway I have tried your great suggestion and there is no spark at all, even tried another new plug but same result no spark, so does that mean the coil is gone ?

May I ask another question ? please, I took the foam air filter out and cleaned it, it was really dirty, I believe you need to put some oil into the cleaned filter, would it have to be the same oil as the mowers engine oil or can you just put some normal car engine oil or other type oil onto the foam filter.

thanks very much for your help, much appreciated.