ok here is the deal . I put on the quadworks kit which is k&n, billet aluminum adaptor,and dynojet jet kit. the quad ran great. then I added a procomp cdi it ran even better. then I put on a hmf full exhaust with recomended jetting and after about 2 hours of riding all heck broke loose. at quarter throttle I have a severe pop in the exhaust about .5 to 1 second apart, here is the worst part, on take off it bogs down to very erratic pops and shutts off. I have been thru 20 different jets, two different types of needles , and every clip adjustment on the needle. the pop and bog never goes away. also did the tape up on the filter, and removed the filter nothing helps. when you cut off the bike you here what sounds like eccess fuel ignite in the exhaust . one time a plug check will reveal lean the next it will reveal a rich condition. I am so lost and disgusted ,I need help could this be a underlying problem like a burnt valve or bad valve adjustment? any help is greatly appreciated , thanks jay

 

Did you retain your air box lid.Your jetting recommendations should be specific about air box lid or no lid so i would keep that in mind.From your description it sounds like you are lean but it is hard to make a guess with the problems you described.If it were me i would start from ground zero and set the needle where it was when it ran good and try the biggest jet and work down from there until you get rid of the problem.You say you removed the filter and i hope you dont mean that literally,that can do damage real fast.If your quad was running good before the jetting changes and air filter exchange then the chances are that it is nothing major but just a fuel and or air issue.Remember take it back to where it was as far as the carb is concerned then jet rich and work down.If carburetor adjustment doesnt help you might try changing back to your stock CDI unit.I had Procom go bad on me and it acted similar to what you are describing.You will get there.

 

Are you familiar with the parking brake rev limiter problem that plagues every yamaha sport quad? Because when the parking brake sensor gets stuck it causes a condition exactly as you described. Try unplugging the parking brake sensor from the harness(follow wires from clutch perch to connectors under the hood, unplug wire with single plastic connector.) I'll bet that's what your problem is, it happens to everyone.

 

Good point Recon.That may be his problem.

 

I'm 99.9% sure of it. When you get a steady low rpm rythmic stumbling/popping there's not much else it could be.

 

Umm i don't really think its a park brake prob. I had the same problem on mine, and i tried the same thing, but come to find out i just had some water in the float bowls, try opening the overflow screws and draining all the old gas out. See if that helps. Mine would run but it would start to pop and backfire at anything over 1/4 throttle. But it would idle fine. So maybe, you have this problem, or i could be wrong and its the neutral safety switch on the parking brake. Peace.

 

If you've tried that many different settings for your jetting and nothing works then thats most likely not the problem. I would establish a jetting baseline and take it from there. With the symptoms your describing your jetting would have to be far off if thats the problem. With your mods I would set the carbs up like this;
Air/fuel mixture screws at 3 turns out using stock pilot jets (22.5 I think).
Dynojet needles on 4th clip using 160/165DJ main jets without the lid. I wouldn't mix Dynojet and Mikuni jets and needles.
These settings should be close enough for you to use as a baseline to search for other problems you might be having.
Next thing I would do (along with what the other guys suggest) is put the stock CDI back in (you really don't need an aftermarket CDI on a stock 660 anyway).
Make sure the intake boot is not ripped or torn and has a good seal.
Make sure the needles are installed properly.......................Good luck!

 

Did you pull your plug? After all the jetting up and down you may have fouled your plug. Just a thought.

 

its not the park brake,that was the first thing I checked,I've been there before

 

ozark I have set it up exactly where you said ,already and it made no difference. does anyone live in or around greenville sc? HELP!!!!!!!!!!!