Small Engines (Lawn Mowers, etc.): Lawn Mower repair, lawn mower repair, inductive timing light

Question
I have a Honda 4.5 GCB135 overhead cam lawnmower approximately 5 years old.

My mower started for the first few years every time, until i serviced it to ensure reliability!

The mower ususally starts first time but since the service last year is unreliable and stalls every 2-3 minutes. We have had severall back fires as well. I have tried letting it tick over for before using it first to warm up, but still stalls after the same time.
Some of your answers on the site indicate it could be the primer bulb, does this sound like that and if so where is it please? I look forward to hearing from you.
Thank you

Answer
Hondas usually aren't equipped with primers.  I think the problem may be related to one of two things.  Check the fuel tank vent for blockage (hole in gas cap is usual location).  Because of the backfiring, it is likely a lean condition caused by lack of fuel.  The other issue may be related to the ignition module malfunctioning once the engine gets warm.  If that is the case, you should be able to quickly check for ignition miss with an inductive timing light (may need a 12V source from car battery if you don't have one powered by its own battery).  Hope this helps.