Hi All, I have been repairing ATV's for many years. Have not done many Hondas.
I have here yet another TRX300A with a NO Spark / Intermittent Spark Issue. I say yet another because after reading the posts here as well as other sites over the past 3 days it seems there is a lot of these. Here is the other thing I noticed. Anyone that has the problem I am about to describe seems to never update the posts with the solution unless it was something simple like a new CDI or other easily swappable part. But the people that have replaced every part and are still having the exact same problem as I am experiencing never seem to come up with an answer to fixing the problem.
So, Here we go.
1994 Honda TRX300A Fourtrax 2WD
ATV is in great physical condition and sat for the last 6 years from a no start issue. No one had worked on it and all the parts were original. I determined right away it had no spark. I went through the entire ATV checking everything. Bought a brand new battery. First I checked all the wires to the CDI Box because I know this seems to be the biggest issue with these. All wiring was good, I especially checked the grounds. A friend has the same model year TRX300A, so I took the CDI and tried it in his ATV. NO Spark.. I ordered a new CDI for this particular model. I also hooked up his CDI into my TRX300 and got no spark. Put it back in his and it works great. Tried the new CDI Box in his and it worked fine. I put in the new CDI and still no spark.. I tested the ignition coil and it was fine. Have a new coil also for testing. Spark Plug Fine, Had a new plug to also test with. Tested the Pick Up coil. Readings were outside the spec so I purchased a new pick up coil. Tested the new one before installing and it was dead on with the spec. I not only used Hondas method of testing in the service manual I also used the specs from rmstator.com , they are a great source of information and specs for individual models. They give you the specs and testing results you should expect. I was having some inconsistent readings from the stator so I got a new one. Just to add, I do have a DVA Adapter. I installed the new Stator and Pick up coil. Once installed they tested to spec. I had been testing the spark the usual way. Remove spark plug , hold it against the head and crank it over. As I had read so many times in different forums, people were getting a brief bright spark from the plug when turning the key on and while cranking the engine you got the same bright spark while switching the Run / KilI switch off and on, but no spark while normally cranking the engine. I was now getting that Bright spark under those same conditions. It seemed the new stator, pick up coil and CDI box were now letting me see a spark. put the old CDI in and no spark at all. So the CDI was bad. I then tested the Neutral reverse switch at the plug and it tested fine. The Neutral and reverse light are also functioning properly. While cranking over the engine checking the Stator showed within spec. Since these have a wire running from the Rectifier to the CDI I got a new Rectifier for testing. Still same spark results. I then went through all the wiring, checking and cleaning all ground contacts. I tested all Handlebar switches and ignition switch for continuity and function. Everything checked out. Checked all fuses and connections. The only suspect connection I found was on the starter switch plug. I completely cleaned it with contact cleaner and it was shining like new. Put in some Dielectric grease and it was good as new. So the only two parts left are the Magnetic Flywheel which has strong magnetism observed while putting in the stator and small encased diode that goes to the neutral light. I have a new diode coming even though this one seems to be testing okay. I guess you could consider the alarm box, but from everything I read it cannot interfere with the spark. Am I wrong?

Does anyone know of someone on this forum that replaced all the parts, still had no spark and was able to figure this problem out?

Thanks for any help, I am stumped as of this moment.

 

Have you tried kick starting it, with the new CDI fitted? Your problem sounds a lot like the "won't spark until you take your finger off the start button" issue. Most owners learn to live with it as, if you keep pressing button on and off, one spark will "catch" and the engine will run. I did cure the fault on a 350 (same CDI as late 300s) It turned out to be the neutral wire. This increases the spark in neutral so, if faulty, doesn't give a powerful enough spark for engine to start when power is also being used by the starter motor. Trouble is, Honda kept changing how that pale green wire worked on the 300, and changing CDIs to suit. Fit the wrong CDI and it will be getting the wrong signal from that green wire.