Backfire while starting?


LawnSite Bronze Member
I have a 2002 Exmark LazerHP with a 23HP kawasaki. Machine and motor have 500hrs.

In the last two weeks, on three seperate occasions when I have tried to start the motor for the first time, the motor backfires during start up. The only other symptom is that on all three times, the motor has had a longer than normal time before it starts...until after it backfires.

Any ideas?

BTW, once it's started, it usually starts fine the rest of the day. Also, I always use the choke with the first startup every day.


LawnSite Fanatic
Just a couple thoughts; I've seen this happen a few times on Dixie Choppers.
Go to cold start, Pull the choke and move throttle to about half, Start cranking and no start after a few seconds of grinding stop move around looking a throttle and choke and take choke off, Then try again and it backfires and starts. I found a intermitting seat safety switch.
After cranking with no ignition the muffler filled with fuel fumes and when moving around on the seat checking things made contact and when it fired caused the backfire.
Have you performed your 300hr valve adjustment check ?
They should be 0.003 to 0.005 both intake and exhaust at top dead center.