View Full Version : Exmark backfire question

04-11-2008, 08:41 PM
I purchased a used 52in Exmark Lazer last year with approximately 2000 hours on it. I believe its a 1996 model, I don't know the hp rating on the motor though it is a Kohler. The problem that I'm having is that its backfiring unless the choke is pulled half way out. With the choke half way out or when the motor is under full load (blades engaged moving forward , choke in) the motor does not backfire. I've changed the plugs and air filter but this seems more like a Lean condition to me. I was told by a mechanic at local landscape company that this could be caused by a leaking intake gasket. Does this seem like a cause or should I be looking at something else. Also what size motor is on this mower? Thanks.

04-11-2008, 10:24 PM
It could be a intake gasket, Check by starting the engine cold then spray WD40 around the intake at the head area. If there is a leak the engine will pick up rpm. Myself, I have found more dirty/restricted carbs (main jet/passages) than intake gaskets.

04-12-2008, 09:30 AM
Thanks Restrorob I will give that a shot. Any idea what HP motor I have here?

Winslow Mountain Lawncare
04-14-2008, 07:31 PM
I had a 1999 52" HP with a 21hp kawi motor that did the same thing. I had the carb rebuilt and it still did it. I found if I shut it off with the throttle just over idle it didnt backfire......I am not sure why but it worked...