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Kyle C Bruno

Need help!! 04 Honda trx300ex

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Hey guys!!

I'm new to the site. But boy am I ready to get down to business. So I have a 2004 honda trx300ex I have videos of it running about a month ago and just today after hours and hours I got it to fire up twice for roughly just a few minutes each time.

I'm having a few dofferent problems...

1. Wiring! I hate it, but needs to be done I have loose wires something else that's broke maybe idk. I can add very detailed pictures as many as needed. The starter button won't work nor will the new ignition.

2. I thought i would rebuild the stock carb I bought a brand new battery new jet kit cleaned out the tank and new fuel lines non-ethanol gas , and by junoibg the relay I crank it over it cranks and cranks kinda sounds like it wants to fire but won't. Bought a new plug I did check to make sure there's spark and there is. But noticing the plug is barely getting wet at all even after cranking it over for a while. So at that point I was convinced my carb was just too far gone even after I cleaned and re jetted. So I purchased a stock 400ex carb firgured why not better air fuel mixture delivery might make a difference and it was a hell of a deal. I got that installed and I finally got it to fire today I'm going to attach the video if it allows me to do so. It seemed to run "ok" but only under consistent throttle. Let off it dies and who knows how long it takes to get started again I worked on getting it started for prolly 3/4 hours today and only got it to start twice.

I did do a compression test when it was cold and it hasn't started yet and was only about 100psi little less. I want to do this myself so I don't get screwed like I did on my other atv 600 dollars later and it won't even run right now. 


Hope to hear back soon


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Welcome to QUADCRAZY! I moved this topic into the Honda forum. Checked out your video and glad you got it running. I noticed you have an aftermarket exhaust. Some exhaust systems require you to re-jet the carb, so you may want to look into that. I had to do that with my HMF pipe. As far as wiring, post the pics and try to get a manual to see if there are wiring diagrams in there. If you don't have one, there is one in the download section:


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The wiring is going to be a big factor here. Only thing on your side is the color coordinated wiring. This should be somewhat easy once you’ve studied and went through the harness. If you can find the manual for this bike just take your time and follow the yellow brick road with the wiring.   I’ve went as far as taking the entire harness off of my bike and hung it on the rafters of my garage and went through it and all made repairs, taped off and respliced  as needed. It’s not as bad as it sounds and takes a lot of the guess work out of the wiring and puts the harness/wiring to rest. As far as carb and compression I am not so sure going with the 400 carb was a good idea but once you get the other issues put to rest you can see how it runs under the 400 carb. Maybe with that aftermarket exhaust you might get lucky. Compression issue sounds normal for a bike that year based on wear and tear it may be ok. I would double check and make sure that the number you seen was accurate. 

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