Hi, my name is Will. I have a 1990 Honda Fourtrax 300 that I bought of craigslist for 400. I knew it had problems and was missing keys. Once I got it home, I wired around the key switch, and I had it running. Afterwards I shut it down and did a few other things, and then went to start it, and crank crank crank, no spark. I checked the coil and plug, both good. Then just reached up and wiggled the CDI, and spark. As time went on, every once in a while it would give me a fit, but i'd just reach up in the front, wiggle the box, and i'd be running in no time. Could this just be a bad connection, bad CDI, or what?

 

CDI boxes fail in numerous ways. Sometimes the potting goo fails and water gets in. Bad solder joints eventually fail, too. Fortunately, aftermarket boxes are cheap, and work well. If you are handy, you can remove the potting compound and find the failed joint (if there) and resolder it. In the case of water intrusion, you can sometimes bring them back by cooking at 250-300F in the oven for 20-30 min.

 

So that was my next thing I was going to say, I purchased a new aftermarket CDI from amazon for 18 bucks. I had the people that bought it from me install it, and it worked. But about 3 days later said they cranked forever and couldn't get it to run. Then they waited 30 mins, tried again and it started and was fine for the rest of the day.

Then about a week goes by, and it won't start again, now they say the oil temp light comes on and wont shut off. So you think it's just a cheap CDI, or something altogether different?

Side note, I own a 1990 myself, so I could take my OEM CDI and plug it into the other one and see if it works.

 

You should try that BEFORE you buy another CDI.

Anyway, lots of possible electrical gremlins to investigate. First, you need an electrical schematic. If you do not want to buy a manual, you can find circuit diagrams online. Could be a bad ground, frayed wire, failing pickup coil, corroded connector, corroded kill switch, etc.

 

I was thinking it was something like that, but I don't think it is, for the reason that you could reach up and wiggle the CDI and it would run, so I think it is a CDI/ stuff in that area problem. Could be a frayed wire that when you wiggle it connects it...? I do own a manual and was studying up on it. I work the these Honda's all the time, I will figure it out, eventually...…..

What do you think about that oil temp light? It has to be related right?

 

Oil light stays on when started, and there is plenty of oil in the engine? Likely damaged wires or corroded connectors. I have never seen a bad oil pressure switch on Hondas. I have had 4 of these TRX300FWs.

Here is what I do with old ATVs that have troubles: remove body panels and pressure-wash everything. Let it dry out, assisting with an air gun in critical areas. Inspect complete harness, and clean up grounding attachments. You may also have hidden wiring problems, such as corroded contacts inside sockets/plugs.

 

I do that whenever I get a new quad, take it outside, degrease and pressure wash it. Everything was nice a clean and working properly. The issue with the light only happened when the new CDI was plugged in. I worked on a buddies Yamaha Bruin 350 and the oil temp light stayed on when the new CDI was installed. So I believe there is a connection, just need to dig farther.

But you probably know WAY more about this than me, so any ideas help for sure.

 

So, I got the problem figured out. When I gave my friend the new box to put in, he by total mistake put in the alarm box slot. As you could guess, this was causing all kinds of issues. I brought both my boxes up, plugged them both in, runs perfect. And even for a test I plugged in the new CDI to the correct port, and it would crank for a few seconds, then the reverse light would come?????

After the fact, I brought his OEM box home and plugged it into mine, with no alarm, and fired right up. An alarm box is on order.

And thanks again sr.ruedas for your help

 

Welcome to the forums.

 

Welcome.