AndrewTG 4 Posted February 2, 2020 My 97 Honda fourtrax 300 Loses spark after getting up to temperature. When the engine is cool (77 degrees or so) the spark the spark plug is strong and the atv works just fine. After i ride it around for a bit maybe 10-15 minutes the spark becomes very weak or nonexistent. Any ideas what this could be? Ive replaced the spark plug, wires, ignition coil, check continuity in all of it, replaced oil. The other weird thing is the oil temp light never comes on other than a few seconds when you start the atv. Share this post Link to post Share on other sites
retro 4,071 Posted February 2, 2020 Hi AndrewTG, welcome to the forum! My first thought is that the ignition coil may be failing. It could be a failing CDI too, or even a pulse generator, or a weak/dead/shorted battery. So I have some questions for you... Are all of the ignition parts on your 300 genuine OEM Honda components, no aftermarket stuff? If not, which parts have been replaced with aftermarket? Is the battery in good condition and does the charging system work? Finally, do you have a multimeter to use for testing and have a copy of the service manual for your 300? 3 Share this post Link to post Share on other sites
AndrewTG 4 Posted February 2, 2020 (edited) The Battery is new. Never fails to start. yes i got OEM honda parts. Yes i have a multi meter and i have service manual. And if you wouldnt mind could you explain to me how the change in engine temperature can affect these parts. We can write off the oil temp sensor be cause the temp light doesnt come on right? Edited February 2, 2020 by AndrewTG Share this post Link to post Share on other sites
Wheeler 2,527 Posted February 2, 2020 The change in engine temp & use of the electrical parts can affect things like the coil. As it’s used with bike running, if it’s defective it will heat up & shut down. When it cools down fire back up... so that’s one example of how the heat can affect how the parts work.. 1 Share this post Link to post Share on other sites
toodeep 1,759 Posted February 2, 2020 In the past the cdi was a very common part to cause this issue. There's not a lot of 300s left running in my area so I had to use "the past". 1 Share this post Link to post Share on other sites
AndrewTG 4 Posted February 2, 2020 Ah i see Thanks for explaining that.The coil was replaced with the Genuine Honda part. So i wouldn't think its the problem. 1 Share this post Link to post Share on other sites
retro 4,071 Posted February 2, 2020 Since all of the parts are OEM and you've replaced the ignition coil, your weak/no spark issue after 15 minutes of runtime is probably with the CDI as @toodeepmentioned. Sometimes you can test the CDI by tapping on it with a plastic screwdriver handle while the motor is running. If the motor stalls or misfires you've confirmed that its going bad. You can also take the CDI off and put it inside an oven with the oven temperature set at about 200 degrees, for about 2-3 hours or so. If the CDI works fine after baking it at 200 degrees then you've confirmed that it was failing, likely due to moisture or cold solder joints inside the potted plastic. But you may just have a corroded ignition fuse socket that is making a poor connection with the fuse, which causes the fuse socket connection to get smokin' hot and fail entirely after a few minutes of runtime. If I were you I would check all of the fuse sockets, make sure they are clean, hold the fuses tightly and show no signs of ever overheating. The next time the motor quits unplug the CDI connector plug and measure the DC voltage between the Black/White stripe wire and ground while the key is on. If you don't measure battery voltage there, then you've found an ignition power supply issue, which might be a bad ignition switch, bad kill switch or just a bad connection inside a harness plug or a fuse socket. The reason why I questioned about aftermarket parts is because they are cheap china garbage which sometimes fries other OEM parts in the ignition system. For instance, china ignition coils are sold completely out of spec, resistance in the primary windings measures so low that those windings act like a short which overloads the CDI and the CDI overheats due to the increase in primary current and it fries. We have dealt with china parts problems a gazillion times over the years. Keep us updated if ya can... 3 Share this post Link to post Share on other sites
toodeep 1,759 Posted February 2, 2020 If you do go aftermarket on the cdi use a Rick's powersport electronics. That's the only one I will use besides OEM. 2 Share this post Link to post Share on other sites
AndrewTG 4 Posted February 2, 2020 Thanks a lot. Im guessing there was mosture in the cdi and the atv is working perfectly after i baked the cdi. I really appreciate your help. 3 Share this post Link to post Share on other sites
bcsman 1,404 Posted February 2, 2020 12 minutes ago, AndrewTG said: Thanks a lot. Im guessing there was mosture in the cdi and the atv is working perfectly after i baked the cdi. I really appreciate your help. Then your next step is to take those connectors and really any others you can easily get at now, blow and clean them out, then seal with dielectric grease. This will ensure any moisture will stay out of those areas. If moisture is getting in any other area the CDI will probably need to be replaced as the baking will get old......If you do alot of riding in mud and water this is especially important to accomplish.... 2 Share this post Link to post Share on other sites
retro 4,071 Posted February 2, 2020 37 minutes ago, AndrewTG said: Thanks a lot. Im guessing there was mosture in the cdi and the atv is working perfectly after i baked the cdi. I really appreciate your help. Wow you're fast with an oven! Odds are that CDI will fail again unless it was just a poor connection in the plug causing the stalling. if you're planning on keeping that 300 you might want to be prepared if/when it loses spark again. Oem Honda or Ricks Motorsport Electrics website ( china fakes are sold elsewhere) are your only choices for replacement. https://www.partzilla.com/catalog/honda/atv/1997/trx300fw-a-fourtrax-300-4x4/wire-harness https://ricksmotorsportelectrics.com/Hot-Shot-Honda-CDI-Box-15_605 As @bcsman mentioned its wise to slather some dielectric grease into both of those CDI connectors as well. Thanks for sharing how you fixed it! 🙂 1 Share this post Link to post Share on other sites
F250 guy 107 Posted February 9, 2020 On 2/2/2020 at 12:15 AM, retro said: Hi AndrewTG, welcome to the forum! My first thought is that the ignition coil may be failing. It could be a failing CDI too, or even a pulse generator, or a weak/dead/shorted battery. So I have some questions for you... Are all of the ignition parts on your 300 genuine OEM Honda components, no aftermarket stuff? If not, which parts have been replaced with aftermarket? Is the battery in good condition and does the charging system work? Finally, do you have a multimeter to use for testing and have a copy of the service manual for your 300? @retro right on. @AndrewTG if ya wanna check the CDI if ya can get to it fast enough if the engine don't kill, tsp with a screwdriver the vibrations should make it get a connection inside. I'd follow retro's advice Chinese or aftermarket electrical parts mean trouble. If your mechanically inclined ya can take every connection down and dielectric grease them so you know their good. Share this post Link to post Share on other sites