I had the same problem. Please u check whether it's neutral or not as stated by Mr. Sammy. Some things which will cause that:
*Ignition timing Off---point gap set too close
(Very sensitive to those 3 conditions)
*Corrosion on the wiring connections between Magneto & coil
*Bad Spark Plug Cap,,,more commonly the Connection between Cap and Plug Wire
---The Plug cap should NOT pull off of the wire with even moderate force.
It's very common for the tip end of the wire to "burn".
This lets the plug cap come off easy.
The Prob with that is it signifies a Bad Connection.
The Cap actually SCREWS on,,it has a long,thin Threaded "spike" which screws into end of plug wire.
Remove the cap from the wire,,,
SNIP about 1/4" off the end of the wire,,
Screw the Cap back onto the wire.
After snipping,,you SHOULD see clean,fresh metal inner cable,,,if not,,,snip a bit more.
CAREFUL not to Shorten the wire too much or it wont reach the plug.
The burning which occurs creates Carbon buildup,,,which is Extremely High Resistance and creates a "semi-insulator".
As simple a thing as it is,,,it can & ROUTINELY DOES seriously degrade spark voltage at the plug.
* Another Possibility especially on ATV is Rusty,Dirty Flywheel &Stator Coils.
This is an Obscure,somewhat Rare fault.
But it happens.
Rustt and dirtt build up over time to create a sort of "conductive mud".
The Flywheel sort of centrifuges it inside the flywheel,,,while scraping away the excess.
Eventually all the clearance is filled with that stuff leaving only a "hair's clearance",,,and it confuses the magnetic flux because there's no distinct beginning or end of Magnet swinging by Coil.
The Flywheel acts like a "Total Ring" of Magnet.
Which having No "Make/Break" of the Mag Flux Field,,,
is effectively the same as Flywheel NOT TURNING.
In Reality it's Never a Absolute,Total condition of that phenomenon.
It's only a PARTIAL condition at most.
But the result of That is the same as having Extremely WEAK Magnets in the flywheel.
Which produces Very Low Voltage.
TECHNICALLY,,a Mag doesnt care if it's Clean or Dirty.
But ATV's typycal useage patterns & conditions Do make them prone to Rust a bit.
Those Rust Particles are the culprit.
Again,,,it's Very Seldom Seen condition,,,but it is something to be aware of-----one of the Mysterious Gremlins which are thought to exist.
Mild examples may cause severe symptoms,,while some really nasty ones seem unaffected.
Unpredictable to say How Bad is Too Bad,,,just no tellin'.
Your Problem is Most Likely either Dirty or Worn-Closed points.
Spam wordSpam word Spam wordSpam word Spam wordSpam word Spam wordSpam word * a sort of TEST method>>>
You can Clean them In Place by sliding a thin strip of sandpaper thru the contacts,,,them spray with Contact Cleaner or even WD40(not a Great Idea 'cuz the oil burns them,,but it does clean them).
then,,,set the Gap to .015~.016".
See it that generates a spark..
If it DOES,,great,,,everything is Functional.
At that moment anyway.
I'm Certain You want to have it Reliable and trouble free all summer long,,at least.
That means :
*Replacing Points & Condensor,,
(Clean the contacts,,they have preservative on them which will burn the contacts prematurely)
*Clean the Flywheel,,
*Spray-clean Stator with some Contact Cleaner,,,
DO NOT Sand on the Coils,,even if they're rusty.
*Polish the Point Cam inside the Flywheel with some oiled 600 Grit wet/dry paper >clean it >apply a Terrible Thin film of hi temp grease,,like automotive wheel bearing grease
Look inside the Plug cap,,,if there's any extreme burning or pitting,,replace it.
Dont forget to snip Plug Wire back to Good Wire.
All takes a Lot more to TELL(and READ,,sorry) than it does to Do.
Once You get it running good,,,
It's worthwhile THEN to try a NGK Iridium Plug,,,,
CR7HIX ( I 'bleive it is)
Wouldnt hurt overall to add a dash of fuel injection cleaner to fuel tank,,
and I'd strongly reccomend using 20w-50 oil,,,and ideally a good Synthetic oil,,Mobil 1 or Amsoil
Here's a Honda Service Manual you can download for Free,,which has all the details of how to set Timing properly
(Ignore the picture of World's Biggest ATC 70,,,lol---the Manual is Correct)
The ignition system on those things is simple and very reliable,,,even if a bit tedious to get set-up correctly
Have a nice time ahead!!!