I run a atv and ski shop in nebraska and this atv has been kicking my butt for some time now. Came in with clutch problems so repaired it and went for test drive and atv ran like crap had no power. I found carb diaphrame bad so i replaced it and still no luck. Atv is runnig so lean im afaird its going to melt down. I have been in the carb several times and put a kit in it. I have checked timming and checked dow pins in flywheel and also cam gear. Adjusted valves and also checked for any intake leaks anywhere. Played with carb and jetting and nothing helps, keep running very lean. I have check spark plug cap and also stator. They both check fine and im not loosing spark at high RPM. Does anyone have a thought? Im leaning towards CDI but not sure. Normaly you dont have spark with a bad CDI and I have great spark.

 

If you apply the choke does it richin up the run mixture? Does it have stock jets and and air filter and exhaust?

 

Is it charging battery?

 

Is atv left brake switch and reverse switch bypassed? on the handle bar ..Look at all of these than get back with us here..Good Luck

 

Sorry forgot to add that to the list of what I have done. I have bypassed both switches and no difference, I have even unplugged tyhem and tryed it but that made it run like it had the reverse rev. limiter on. and does not change if I pull the choke. Yes the battery is charging as well. I have been doing this work for awhile and Im realy stumped guys. At this point I have lost my butt on this job and now its just try to fix to keep the customer happy and not lose my mind. Thanks for the response guys. Is there a chance the CDI is bad where it sparks fine just not the right fuel curve or timing. The carb setting are stock and exaust. But It does have a K&N with the air box lide on. The exaust is not plugged either.

 

Ok explain you lean running? Duct tape to air cleaner lid to see if to much air an not enuff fuel to run. Did customer tell you its always ran like this?

 

Have you checked the peek voltage at the plug ?

 

In stead of duct tape just block k&n lid with something to cut down air flow to see if it changed things....Like remove lid an placed an shop towel over box and snap the lid over towel so towel wont get suck up into carb..

 

I have put my hand over the opening half way and it kills it. I have put a killavolt spark tester on it and it jumps all the way to 35 and keeps running. It starts and idels great but half to full throttle it has no power so you have to shify early in every gear. I will ride it around are shop come in and check the plug and its so white and the head pipe is glowing.

 

Has engine been rebored? Is exhaust opened?Have you put an timing light on flywheel mark to see if ignition is advancing?