Alot of time when a regulator spikes it gets CDI also at some time I would replace both but do one at a time so you will know which was the issue

 

I guess a crazy problem would lead to a crazy solution. I was about to order a CDI and regulator online when I decided to go to the garage and take a picture of the plug orientation of the CDI. When I removed the CDI I was surprised to notice that the alarm box was the same size as the CDI and had white plugs. I remembered seeing a little square CDI box in a bunch of spare parts the PO gave me. Found it and it had green connectors. Okay, let me swap it for the other one in the alarm position. First thing I noticed after hooking it up and turning the key was that my oil light came on for a few seconds and went out. The oil light has never worked since I bought the ATV and I planned to fix it later. Start it up and it is running great, heck battery voltage and it is charging at 13.2, rev it up and never goes over 14.4. I think the PO put a CDI box in place of the alarm and it was causing the issue. I will spend sometime riding it and checking, but it is running great with no lights on. Crazy, I know.

 

As papa hog scoot wrote, keep an eye on that regulator, it may overcharge again and CDIs don't last long when fed with high voltages. If you do change the regulator, as with CDIs, Honda had fun with altering them between model years, if I remember rightly 5 wire, with red and green going to bullet connectors, or 6 wire with red, green and black to bullets, or one with the bullets changed to a block, spade connector. Aftermarket regs for 300s seem to last OK, unlike 350s and 420s, where we have had real problems with RM stator regs. Bronco have been better.

 

Update number...who knows! busy week finally back to diagnosing this thing. I don't want to just throw parts at it. When I got the machine the rear diff was locked up and the starter was melted inside. I tackled those before trying to get it to run. It cam with a box of parts that screamed "I can't fix this thing!". The PO had filled the box with a couple of carbs, coil, alarm box, two starter relays, etc. On the bike it was obvious it recently had a rectifier, stator, CDI, and another starter relay. After putting on a new starter, setting the valves, and putting on the ebay carb it fired right up and had the crazy miss on anything past idle. You guys pick up this original post from there. So all I have determined so far is that the stator puts out 54V AC cranking, the rectifier starts at 14.4 on crank up at idle and begins climbing, after the battery voltage gets past 14.8 the CDI begins to act like it is on a rev limiter, after a few minutes of running the voltage will climb to 15.8-16.5. So since the PO already replaced the stator, CDI, and rectifier I don't want to just replace all three again. QUESTION: Since the CDI receives it's voltage (AC) from the stator yellow wire and not the rectifier (DC) does it matter if the rectifier is bad? If the CDI is breaking up as the bike warms up is it the stator that would cause it? How would a bad rectifier (DC voltage) effect the AC fired CDI? As best I can tell the battery voltage shouldn't affect CDI performance since the TRX300FW uses a dual voltage system, AC for ignition and DC for starting and lights. So do I throw a stator on it even though this one seems in spec? Try a new CDI? Put a rectifier on because this one obviously isn't controlling battery voltage correctly? Ideas?

 

That yellow wire to CDI is one of life's little mysteries as it is a DC CDI, so is fed pos from ignition switch, and stops sparking when you turn the ignition off. I suspect the yellow is used to "sense" output from stator and, therefore, revs, so controlling advance retard and rev limiter inside the CDI. Anyway, the voltage fed to the CDI from the ignition is the important bit and the regulator is entirely responsible, if it goes over 14.5v change it now. I once fitted a new CDI to a 300 and had it blow within one day. Checked and the reg was overcharging, whether I forgot to check when I fitted the first new CDI, or it was an intermittent overcharger, I'm not sure, but I had wasted a CDI.

 

Thanks, part is on the way!

 

Update time. I think it is fixed! Lol! So I put another rectifier on it and same problem. It would run decent at first and as it warmed up it would hit a rev limiter on anything over idle. I also ordered a CDI box (ebay special) that said it was for the 88-94 model. it has the red connector like the one on it now. When I pulled the old CDI off it had the connecter on the opposite side of the box than the new one. I was a little nervous about putting it on but though what can I loose since nothing has fixed this machine. Well the new CDI was the right CDI. It started right up and idled smoother than ever. I could really tell a difference right away. Rode it around for a while and it had more power and much smoother acceleration. The big test was what happened when it warmed up. Nothing! It kept running great. With the old CDI I would have to turn on the lights once warmed up for it to accelerate at all, and it still wasn't smooth. It seems they will run with the 94-99 CDI but not run right. Or this CDI was just cooked. I have another CDI with the connector on the same side as the old one but it has white connectors. I may hook it up just to see if the newer style is the issue.