Craftsman LT4000 spitting/sputtering and backfiring after riding for 5mins

cjones636 said:
Did that today...

Replaced fuel lines, Cleaned tank, added a new filter (air and fuel), rebuilt carb.... Still done the same thing..... But, as soon as it went dead i jumped off the mower and checked the spark again, and the spark was orange, not blue!
Click to expand...

Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap.
 
Is that a Walbro LMK carburetor..? if not can you post the numbers that are on it..!
 
Since you have a number of issues I will chime in on general engine basis. I have said before that the coils may not be just coils and may be helped with electronics components such as capacitors and transistors. These are produced in levels to withstand heat. I'm guessing if they are there they are not the best and may fail. Typical failed transistor response at hot is to quit working until cool. Next this float deal. In the good ole days there were specs for float stroke- you bent a tang for full droop (bowl low) and one for shut off (inlet valve shut). These settings were provided by the engine manufacturer. Otherwise starvation or flooding could result. Also on wide open throttle the combustion pressures are max which can expose a weak spark. I have been where you are and it drives you nuts. Good luck:thumbsup:
 
Find the tag on your engine and post it's model and spec numbers.
 
Just plug in a good plug on your coil lead, and hold the side of the plug against the block to test.
 
Fish said:
Find the tag on your engine and post it's model and spec numbers.
Click to expand...

Wouldn't make any differences by the engine number, someone may have fitted a different carb to it, that is why I ask if it was a LMK.
 
EngineMan said:
Wouldn't make any differences by the engine number, someone may have fitted a different carb to it, that is why I ask if it was a LMK.
Click to expand...

I Did purchase the mower from a local repair shop years ago, but it ran fine up until late last year.
 
You must log in or register to reply here.
Back
Top