my bike is backfiring at half throttle and up, cleaned carbs and just about anything you can think of. Is it possible that the rear cylinder is out of time.Replaced choke spring changed all eletronics from freinds bike.at the end of the line on this one please help

 

ASSUMING YOUR QUAD WAS not in reverse & RUNNING FINE & SYMPTONS STARTED OUT OF THE BLUE and fuel switch/lever is all the way on.

1st check oil Level & your CVT belt trip switch, (oil no more than half full & switch not tripped reset it for GP) 2nd swap out the CDI, to see if its the culprit. 3rd ensure no vaccum hoses are missing/clogged to/from your airbox. 4th Pull out your Main jets and pilot jets and blow them out with air & inspect for any obstructions. 5th if not fixed take top off of carbs and ensure spring/spacers diaphrams serviceable & are correctly installed & no grit is in the Brass O-ring hole in cap seal & seal properly in groove. 6th ensure BOTH your carb manifold to eng and carb to airbox clamps are tight and boots not torn or missing carb SYNC air nipples. Ensure sparkplugs/caps and top of head not caked with mud.


Also Fresh Gas, ensure you got a clean non over-oiled air filter, and or flush carbs/fuel /petcock line, Ensure no Critters have crawled in your snorkel, check spark plug wires for bad wires or caps. Last, Pull seat and inspect wiring for chaffing/short, pull all fuses, inspect bend ends slightly, coat with Diaelectic grease and reinstall.

Let us know what you find[img]i/expressions/face-icon-small-cool.gif[/img]

 

[img]i/expressions/face-icon-small-sad.gif[/img] tried all of your comments from plugs to carbs plug wires im not an electricion but when bike is running at idle we check the voltage at the coils with multimeter the coil on the rear cylinder is reading much different than the front cylinder coil.Ialso have a brute force and it reads the same on both coils.already changed cdi and all other electric parts from another 700 p. gas has been changed 3 tanks full not that.I have seen another forum that said his rear timing chain might have jumped one tooth.Could this be the gremlin or what else could i try.all the comments that you said i tried before and checked again.AT THE END OF MY ROPE.Thanx for your help

 

Bruster
Couple more.

Yes its possible your Bike jumped time. Have to find someone that knows how to check it. In the interim, Check out your flywheel key to ensure its not broke and while you are in there check out the Magneto pickup (What ever they call it) but it reads crank position (look in a wiring diagram; maybe call the crank position diode/photocell?)

Hopefully you haven't overlooked a chaffed wire under your seat or from CVT or have an accessory thats grounding/shorting out to on of your main electrical lines to CDI.

Will it run by just adding cas to the carb? to rule out your fuel pump?