25hp johnson backfiring

[sambrigman]

motor will not start, but is back firing thru prop, the plug wires are not reversed, and I pulled the flywheel, everything looked good, key is not sheered. To make things more complicated, some times there is no fire! This motor has never give any problem, this all started here the yard. I have replaced the switch and power pack.All this makes no sense to me, any ideas greatly appreciated

 

[w2much]

Check all electrical connections, plugs ,grounds, frayed wires kill switch ect.Check your electrical connections with your manual.

 

[racerone]

??---Is the orange / blue stripe wire on the top coil ?

 

[sambrigman]

yes,the orange/blue is on the top coil. Still backfires

 

[racerone]

Sounds like the throttle is opening too soon .---The other possibility is the low speed jet needs to be opened up.

 

[tommarvin]

Its spark or fuel, are you sure you have spark, test with a spark checker. Are the carb jets clean ?

Take the cowling off, with a flashlight and your glasses on, check every single electrical connection carefully.

Now check all the rubber hoses for cracks or leaks, check all springs, check the choke if its stuck closed.

My gut says its electrical,