I just joined this forum because I've been reading your posts and seem to be having the exact same problem.
I have a '92 TRX-300FW that stopped running suddenly one day. I wasn't there when it happened, but it sounded like an electrical problem.
It's started once or twice since, but doesn't run long. I've pulled out the stator, and pulser but both check out.
I took the regulator/rectifyer to the dealer with me, but I was told that it had to be on the quad to test it?? I pulled the stator
due to a friends assertion that the stator wasn't making much power. I'm going to put it all back together and check it myself.

If you find somthing, please let me know at gil2264cup@yahoo.com

Thanks,
Dan

 

Well, more correctly, you need the machine to really check it out thoroughly. You can test the diodes, which is your concern here anyway. To test the regulator function, you need the machine running to check out the DCV dynamically. One other test relating to the reg\rect (not that it's gonna solve anybody's problem here but it never hurts to be thorough), is to check for battery voltage TO the unit. It will not do its job unless it's powered up. Unplug the reg\rect and turn the key on (some models the reg\rect is even powered with the key off). Check for power on the two red (+) and green (-) leads to the unit. If you don't have it, you got a blown main fuse, which of course would be obvious to most people already, or a wiring problem. As far as stator AC output tests, they are a good thing, but can be deceiving. They depend on how fast the engine is turning over and of course temperature. So if you are testing with a weak battery, your gonna have low stator output.

 

I reassembled the stator and rectifyer. When cranking with the starter, I get 8 volts AC between any 2 of 3 phases going to the rectifyer and 8 volts between the lead going to the ignition system and 2 of the leads going to the rectifyer. I think the ignition lead is tied into the other phase. At the same time I get 8 volts DC out of the rectifyer. So those both seem to be in good shape.
The neutral, reverse, and oil temp interlocks all seem to be working. The key switch and kill switch are good so that seems to leave the two black boxes in front of the steering column, and the ignition coil. I don't know of any way to test the black boxes, except to switch them out. I don't know any one with the same model, and the dealer wont take back any electrical parts if they don't solve the problem. There's a diode in front of the steering column, but it checks out.

That pretty much leaves the ignition coil to test. Does anyone know what the resistance should be across it...and NO I'm Not going to hold the tip of the spark plug and juice it. So don't suggest it...been there, done that.

If you see anything suspect please let me know.

 

You should have a very low resistance across the primary side, like .6 to 4.0 ohms. The secondary circuit of the ignition coil should read in Kohms between 4Kohm and 20Kohm depending on if the resistor cap is removed. These are off the top of my head figures and maybe somebody here with a shop manual can give you exact spec. You are right about the box, there is no reliable way to test it except try a known good. The ignition coil is very reliable and is uncommon to fail, but you are right to test it.

 

After rereading your post, 8VAC does seem kinda low for stator output. See if you can find another one to compare it with your meter. If you haven't done it already (you seem pretty thorough), unplug your stator and make sure the yellow wires of the stator side are completely insulated from ground. If you have even a very high resistance, your stator is faulty.

 

I feel your pain, Gomer11. I do have a service manual for the 89 thru 96 trx 300fw, so if u want some specs from this book, just ask for them. I could email scanned images if you would like to get them.

I really have not had much time to look into mine as of late, but I will be getting back to it hopefully tonight. Of course, if you get it to work, I do want to know what the problem turned out to be since it is probably the same as mine. As for 8VAC, if this is cranking voltage, then I think that this should be accurate. I am getting 6.9VAC after I recharged my battery to get my cranking speed back up.

Dzzy does seem to know his stuff, and based on previous posts that I have seen, he is pretty accurate. I am however still hoping that he might have a revelation on this problem and help you and I both out; and at the same time look like a miracle worker. I know that he will to me anyway.

I trouble shoot this type of problem all the time, and have never had one stump me to this point. Granted, I usually troubleshoot Kawasaki and Suzuki, but I would not have ever thought that Honda would have ever been this difficult. Maybe I am just unlucky with this one, but now that you are having the same issue, I am reconsidering my theories. I am not saying that Honda is a bad machine, it is just this one is giving me a run for my sanity.

I will keep posting until this issue is resolved, one way or another.

 

Those sound like low VAC on the stator windings, even for cranking speeds. Unless you're engine is turning over really slow. Maybe A couple of these other tech guys on here have done a reading on one recently. We do have a lot "rat" 300FW at work, suppose I could do a cranking test on that one. It's laughably beat up but it runs fairly decent. Have you guys checked to see if your stator yellow wires are grounded by any chance? If they are in any way, your stator IS toast. You both sound pretty proficient and probably know this, but you do that test with the stator unplugged. VAC cranking test too by the way.

 

It is a miracle. I finally found it.

OK, I think that it was purely by luck that I found the problem, but I figured that everyone would like to know what the final solution turned out to be. I had decided not to mess with it for a while, mainly because it had thouroghly ticked me off, but I finally decided to look at it again on Saturday afternoon.

To my surprise, I plugged everything back in, and I saw spark. I was surprised, and thrilled, all at the same time. I then mounted the CDI box back to the vehicle, tested it again, and it was broke. I then unmounted the CDI, and it was still broke. I pulled on the CDI to slightly strech the wires, and it momentarily worked. Anyway, I moved wires, boxes, and many other things before I finally narowed it down to one wire. If I just barely touched the wire, it worked every time.

The problem turned out to be the ground (green) wire connector at the CDI box itself. This is the only place that you cannot test for a good connection. I pulled the pin from the connector, tightend the crimp on the end with my pliers, replaced it back into the connector plug, and everything worked great. I was unable to make it fail after that. I unplugged the connector, placed new connection grease on it, and put the whole thing back together.

I would like to thank everyone for their suggestions. I was at my whitz end on this. I did go back and tried the old CDI, and it was bad. My guess is that it was fried by the intermittent lose ground connection, so I did not waste and money or parts, just a lot of time trying to solve this.

Hopefully, this is Gomer11's problem as well so that he can finish up on his nightmare.

Thanks for all of your advise dzzy, it did keep me going on the right path.

As this is now working, I am going to call this complete. I returned the ATV to its rightful owner, and was glad to see it go. Now maybe I can finally work on my own equipment for awhile.

 

Good job it's good to hear you got it back working! My Friend has a bike just like yours so this is verry usefull I willkeep this in mind if he has any problems like this!

 

Good job MacGyver. A very tricky problem to solve. I have a Honda special tool in my box at work that is like a key chain with various male terminal ends that Honda uses. It's for inserting into the coupler to check for a loose fitting. It's pretty cheap for a special tool and probably could have helped you out in this circumstance. If you do a lot of electrical troubleshooting it's probably not a bad investment.