This one has me puzzled. I admit that I have not gone through all the "no spark" testing because:
When the ATV starts it will run for hours without any problem. The risk is when you shut it off. Sometimes it will not start again. It could be 1 min or 10 hrs, no rhyme or reason.
Right now it is stuck out back in the field. Drove it out for probably 1/2 hour no problem. Stopped it and left it for maybe 2 hrs. Went to move it 0 wont start. Pull the plug, no spark.
This same scenario has happened more times than I can even count. Maybe tomorrow when I go pick it up it will have spark and I will drive it home. If not I will tow it back, put it in the barn and start trying to figure out why there is no spark.
BUT, what will likely happen is all of a sudden it will get spark while I am trying to figure out why it has no spark. Once it decides to spark, it will continue to do so under the next time it decides to leave me stranded.
Any idea what could be causing this erratic behavior?
Any thoughts would be helpful...

 

Intermittent electrical faults are the worst to find, you just have to catch it with the fault "on" and do some tests, hopefully finding something before the fault goes off again. KLF300s are easier than most, as it uses a 1980s car ignition system. 12v coil wired to the ignition switch, pick up coil on flywheel and "ignitor box" to send a negative pulse to coil when the pick up signal tells it to. Ignitor has a pos from ignition switch, and neg feed wire, but that is it, no kill wire, no "exciter coil" to go wrong. One thing worth checking is the voltage regulator as, because the ignition is battery powered, overcharging regulators feed too many volts into the ignitor and slow cook it.

 

That has been my problem - trying to diagnose when the fault exists. Last time all I did was wiggle the wires going to the stator and I got spark - figured there was a short in the wire. So when it faulted again,I just wiggled the wires - no go. That was just a fluke (as it always seems to be. Since I have a spare regulator, I will swap it out and my guess will be that I will get spark (BTW - has a new coil). My guess is I will get spark when I swap out the regulator, but will probably be another false fix.
What puzzles me is that it will run forever once it starts. The fault only occurs after you shut it off and try to start it again. That should be a big clue, but I dont know what that is

 

Any luck with your spark issue? I'm having the same problem.

 

Any luck with your spark issue? I'm having the same issue.

 

I had the same problem until i recently fully diagnosed the problem. I started from the end of the process and worked my way back. I would start with the spark plug see if it has spark.
Then test the plug boot do this with a screw driver on the boot next to the block.if your getting a stronger spark without the spark plug then with it look into the boot. see if it has an actual connector I had a clothespin spring in there I replaced it with the proper connector and it went from problematic to repeatable. Keep working back from there also check your electrical connector on the rectifier if it looks burnt replace it.

 

did you get it running?

 

also try replacing the pulse coil. Ive heard they can fail and be intermittently functional and impossible to diagnose without replacement.