Motorcycle Repair: Yamaha Maxim 550, stator assembly, spark plug wire

Question
Hi I have a yamaha maxim 550 1982 I had it out one day it was running perfect . I parked in my barn for the night . I went to start it next morning, It started but it was running really rough , everytime I would try to rev it to 3000 rpm it would start breaking up and backfiring then stall. so far I have taken the carb apart cleaned all the jets , put in new plugs , put in another tci unit , all cylinders are getting compression ,I had the coils tested and put a new air filter. It gets spark. I'm totally stumped.

Answer
Manny,
  Check high tension coil wire (spark plug wire) and it's plug cap.  It's possible there is a worn connection.  Make sure there is no moisture or oil invading the stator assembly.  Also, not probable however, check that you are receiving a full 14-14.5 volts at the battery terminals while idleing (900-1100 rpms).  This will give you a basic impression on if the stator is measuring up to the load demand put on it.  In addition it will tell you if your voltage regulator and rectifier are working correctly.  It's possible to have spark yet not enough current to effectivly fire the full mixture or it may be a sporadic spark not detectable to the eye.  It's possible for coils to show ok resistance readings upon test and fail spoadically once in use, typically if the coils are above the cylinders and heat up a fair amount.  Try to test them at operating tempature right there on the bike, right after running it and experiencing the misfiring.  Ignition modules can be faulty and the easiest way to troubleshoot them is swap in another like you did however, be absoulutly sure it is a working one, i.e. from another running model.
 Other than this, if the carb is in fact, cleaned and adjusted properly, you may have filled up w/ some questionable fuel, a simple but often overlooked problem.  Here is some info I've given others on dealing with carbs:

Be absoulutly sure all orrifaces and jets are clean and clear, not damaged. Clean with solvent and COMPRESSED AIR ONLY. Never use picks or wire to clean out any jets or orrifaces. If someone used anything but compressed air and solvents to clean these they could have damaged the precise venturi action that takes place. Carburators can get pretty complex and require tuning from time to time. In addition there are different systems and effects that come into play at different throttle positions. Like your system, performance can be fine at one throttle position and terrible at another. All you can do is look closely for damage and carefully adjust all tolorances according to a good service manual. Do not overlook the float level, be very sure you are not starving for fuel. In relation make sure fuel flow is unobstructed and use a good in-line fuel filter from the tank to the carb. Even tiny particles in the fuel can get logged in critical areas and cause havoc.

Mike