I was riding four wheeler yesterday..i was sitting there idling....and engine died. I kept trying to start it and it wouldnt start. when i got home i took air filter off of front of carb, and i can see that it is shooting gas...I then pulled spark plug from engine and put in wire...i held the wire with pair of pliers and turned motor over....the spark plug is not sparking. I replaced spark plug. Did same routine, and still no spark. Anyone had to replace wire/coil assembly? Do you think that thats the possible problem? Is there a way to test the coil? i see that it has 2 leads...Any help would be appreciated. Thanks

 

Disconnect black wire from CDI module harness,this is kill switch wire,See if have spark then, if have spark probable cdi bad internal short or can be left control switch short,if still no spark then have to check stator specs. Also check coil connection and resistance specs. Can be some simple as a plug wire broken internally or stator problems such as the trigger(pulse coil) coil! HAVENT had to replace a coil in years ,even though customers bring em in so I can test on a coil checker! Ohm meter a good investment if you dont have one! You dont have to get an expensive one!

 

ok..I waited till it was dark and went back outside so that i could see sparks easier..I pulled plug from block and put back into spark plug wire..Holding the head part of the wire that snaps onto the plug with a pair of channel locks(rubber on outside so it wouldnt shock me). I did same test...and i could see sparks. I put plug back in and put wire back on and tried to start it. It fired right up. I ran it and killed it. I tried to start it again and same thing happened. It wouldnt start. I pulled plug back out and did what you said( disconnected black wire from cdi). Tried starting and plug was sparking. I reconnected black wire from cdi. tried starting and it sparked a few times and then stopped sparking at tip of spark plug..BUT I could see that it was sparking from my channel locks to where i was holding the head of the wire connector..like it was arking through the head to the channel locks (the part that snaps onto the plug). Not sure if thats normal. I dont think it is..The first time i did the test i just held the wire connector with my hand it it actually shocked me when i turned it over(I wasnt touching the plug at all). Maybe a bad CDI like you said because of it sparking when the black wire is disconnected, but the only catch to me is that i see it sparking down at the head of the wire to my channel locks where im holding it, but not at the tip of the spark plug... so to me it seems like the spark is going down through the wire, but not through to the spark plug. Correct me if im wrong. Like I said im not sure if it is suppose to spark like that through the head to my channel locks. Im thinking bad wire....on my atv wire/coil come together as one unit..I appreciate the help..If you think it is still a bad cdi let me know..

 

Can replace wire if bad ,just get some 7mm wire from auto store! SCREW wire into coil first,then screw into plug boot. See if starts with black wire plugged into cdi.If only cranks with wire unplugged,CHECK first for shorts in left control switch harness. if that is ok then probably cdi internal short. ALSO not common but 5k ohm plug cap can be bad(resistor shorted out) Keep us posted.

 

my coil and wire are one solid piece...they dont come apart that i can see...and i believe they are sold as one unit..Looks about 105 bucks from looking online. CDI around 250 bucks. and what do u mean the resistor in the cap can go bad? is that something you can replace? or do I have to buy the entire coil/wire assembly? My cap does say 5k ohms on it...I tested it again today at night, and it did the same thing..it would spark at the tip of the spark plug a few times and then stop, but it would be sparking continuously from the cap to my channel locks..also i could see that the wire was sparking when it would get near the frame of the atv..What your saying about the resistor in the cap kinda makes sense because it seems like its sparking normally from the things i can see from what i just mentioned above..Its just not getting to the tip of the spark plug. So do u suggest I purchase the coil/wire assembly?

 

Resistor plug cap could be bad/ cracked (not common,but can happen) If sparking with cap off if thats what you are saying CDI not bad! Try cap replacement first. Can purchase NGK replacement cap separate. Try this before spending money on a coil!

 

I saw this and am having the same problem. I disconnected black wire from CDI. IT started and would not turn off with key or control switch. Any advice?

 

you unplugged the wrong wire. two black wires. one fixes the problem other one fixes problem but wont let you kill motor.

 

After letting run for about 10 minutes, it got warm and fan did not turn on? Unplugged wires off thermostat and jumped them, fan kicked on. Could it be getting to hot and killing motor on its on?

 

two different things. what model do you have?