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electrical or jetting issue? lost at where to start


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03 banshee, 3hours on 392cc athena top end. open air box with proflow airfilter, stock carbs with 27.5 pilots and 340 mains, needle in 2nd clip position from top. Was starting and running ok when cold, bit of back firing and popping down low once hot. absolutely no bottom end but excellent once it gets the revs up. thought it was just how banshees were until riding a friends 07 which was very smooth and nicer to ride. half way through a ride and the left cylinder ( main one that backfires) dropped out completely. bike still run, after giving it some throttle in neutral the left fires back up once the revs pick up but drops out again down low. spark seems a little bit erratic/non consistent. I have tried new plugs and nothing has changed, carbs are in sync, i did get an electrical shock through the bars when it was running and i didnt have my glove on, could it possibly be a short somewhere? any help will be appreciated

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i would start by ohming.  sounds like possibly a plug cap, or the plug wire, but it could also be explained if the plug is not firing.  what do the plugs look like?  that tells allot.  have you even checked that there is good blue spark?

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plugs are ok, i did have it on the 3rd clip position but was a little rich so changed back. brand new plugs in now. when it does spark it is a nice blue, just  doesnt seem to fire every time. iv replaced the plug caps and the spark is still the same. just cant get it started at all now, it coughs and carrys on but wont run. cheers for the quick reply, il borrow a multi meter once im home and start checking the wiring.

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I havnt even considered checking the pick up gap until now, to be completely honest I didnt even know what it was until now... I will check it out, how do I adjust it properly? And cheers for your 2 cents, the more I learn about this thing the better as I cant stand anyone else touching my bike... Can you change out the spark plug leads or do you have to change out the whole coil if they were fucked?

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remove the flywheel cover ( left side )

it's on the bottom right to the flywheel. It's the pickup for the CDI box. There is the two raised notches along the outside of the flywheel. Those trigger a spark. So if it's too close it wrecks the pickup because it'll hit it. Too far and it runs funny. You can loosen the few screws and or bend the tab it's mounted on.

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you can also just use the box your spark-plug came in.  stick the flap in there and adjust it agaist it.  tighten up, and you should be able to pull the flap out.   check on both sides.   if you are only sparking like every 3rd time, it does sound like your stator is probably shot.  that is a sign that the cdi is not being charged fast enough.   that could also be a probalem with the flywheel magnets.  do not remove the flywheel with anything but the flywheel puller made for it.

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get a new/ used OEM one.

 

also  the athena's port timings are retarded high for a "rider" bike.  the only one i have been around was a bitch to tune also.  i didnt assemble the motor just tried to get SOME low end middle rang e power out of it.  wasnt good to great by any means.  but screamed on top.   the best jetting i had found was total crap one clip positions off..  they were that sensitive.  its possible that a bad assembly or huge mis matches internally ( porting wise) were also contributing to the lack of low end.

 

stock banshee's actually make pretty decent power compared to other "stock" atv's..  

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hey guys, cheers for the help. Pick up coil was a long way out, reset that and the spark is excellent now... tried to fire it up and still a no go... did a comp test and had about 5 psi in the left, i am having the best luck with this bike! pulled the head and the left piston has broken the crown down to just below the top ring, about 5mm deep, intake side. there is no marks in the bore, nothing to indicate a  snagged ring, what else would cause this? Im slightly pissed off with it as its barely run in, could it just be a shit piston? the top end was a complete 392cc athena kit

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