One thing I did not mention. The rope on the recoil pull starter broke before all this trouble started. I am wondering now if there is debris in the stator housing that may be interfering with the pick up coil performance. I will tear it apart and inspect it.

 

Absolutely this could very well be the problem. Look at this post from another member that had the same thing happen.http://forums.atvconnection.com/pola...ml#post3155476

 

Well, I removed the recoil housing this morning with the intent of looking for debris from the broken recoil rope. There was about a tablespoon full of finely ground up nylon rope near the starter gear/flywheel interface so I pulled it off and vacuumed all the nylon rope debris from the engine housing and the recoil housing. There was not a lot but just enough to keep me thinking on this. Next I located the pick-up coil at about the 7 o'clock position behind the flywheel and like the other ATV Forum member, I noticed the pick up coil gap to the flywheel was about 1/4 to 3/8" - way too much! It had been bent out of the way by the knot from the broken nylon rope that was apparently rattling around in the recoil housing while the engine was running! The knot got caught between the flywheel and the pick up and bent it back out of the way enough to cause the no spark issue.
I gently took a small prybar and screwdriver to bend the pick up coil back to maybe a 1mm gap to the flywheel magnet. I re-installed the rope in the recoil housing. Buttoned everything up and she turned over immediately!
Wow this was definitely one of the most difficult small engine diagnosis I ever encountered.
Be sure to share this no spark failure mode with all the folks out there that get the broken recoil rope then no spark failure.
Thanks for all the help!

 

Glad you solved your problem. Getting to be that this is a common problem with the 500 when a rope breaks..

 

When you said "The rope on the recoil pull starter broke before all this trouble started." I figured that was the problem.

 

Yes if that "minor point" had been posted earlier it could have saved him the price of a cdi also. Some people do forget on some things happening or may not think they are worth mentioning,plus none of us can remember everything for people to check out either. I've had some people that it felt like pulling teeth to get some more info out of them so people could help them.

 

OPT. I have another question for you. I was putting the 2003 330 Trail Boss out on the trails today. Runs great as I now have a new carburetor, new fuel pump, spark plug, new fuel lines and battery after my ordeal with the broken pull start cord.
Anyway with the new carburetor, it starts and idles great and runs excellent to about 2/3 to 3/4 throttle. Past 3/4 throttle to WOT is bogs like it is starving for gas. With all the new components and given that is runs great at idle to 2/3 throttle I am thinking the new carb has the wrong high speed jet i.e. running too lean. I also noticed these carbs have no adjustments.
Anyway, I still have the original Mikuni carb which was fine at WOT. I am wondering if I should clean out the original carburetor and re-intall it on the ATV. Alternately is there any way I can adjust the new carburetor? Again I see no low and high speed adjustment screws on these carburetors.

 

Check the jetting in the oem Mikuni versus the after market carb and see if they are the same.That may be part of the problem If the jets are smaller in the new carb.Those can be swapped over if necessary. On your oem Mikuni the pilot screw(idle fuel screw) was blocked off by an aluminum plug from the factory. If it's missing then someone has removed it.Normal setting on the pilot screw was 2-2.5 turns out from a lightly seated position. If the new carb is plugged,you can drill it out carefully. Just drill an 1/8" hole through the plug and use a drywall screw to remove it. Then you can see how many turns this screw is set at. It may be set too lean or too rich. My two cents is the oem Mikuni is the best carb versus any of these Chinese after market carbs..

 

I checked the OEM Mikuni carburetor and the idle mixure screw was set at 1 turn from lightly seated position. If I opened it up to two turns then it would run richer/more fuel mixture?


Also, The brass nut that screws into the carb on the choke cable is extremely difficult to remove. I bought a cheap 12mm open end wrench and ground it down so I could get it off the Mikuni OE carb. What kind of tool have you found is best for removing this brass choke cable adaptor and can I buy a replacement that has the 10mm nut formation on the end near the cable like some of the 500cc model carbs?


If I can get the brass nut off the new carb I will swap the OEM carburetor on it again and test drive. If I cannot get it off, I will probably just swap the jets as I suspect the OEM carb jets are probably larger.

 

Just like you I ground down a cheap 12mm open end wrench to fit the nut that's jammed tight on the carb. They have these special wrenches on the tool trucks but I was too cheap... Just takes a little time to turn the nut to where you can finish unscrewing it with your fingers. On the carb 1 turn usually isn't enough depending on what jetting it has.. This is called the pilot or idle mixture screw that mainly adjusts fuel to incoming air at an idle. Again if it's jetted right 2-2.5 turns is normally what you'll find,sometimes 3 turns out. On oem carbs on a few Trail Bosses and Blazers I found a couple at a half turn out and one was actually closed off. That explained the hard starting and having to keep the choke on these. Once I set them at 2 turns,no problems on cranking and fast warm ups.