Chesnuts54 15 Posted October 23, 2023 So I just completed this next step and it looks like we did not record any AC voltages at all. It did not come off of 0V AC. So we can assume that the new cdi does not work? I also tried my old one as well. But like I said the old one smells like burnt plastic unlike the new one! Share this post Link to post Share on other sites
retro 4,048 Posted October 23, 2023 Yeah, the used CDI appears to be dead. Lets complete the tests on the CDI connector before you replace that CDI though. With the CDI unplugged, your meter on DC volts mode, Ignition key on, measure DC volts between the Black/green wire terminal inside the CDI harness connector and frame ground. You should see battery voltage. Last one.... CDI unplugged, Ignition key off, multimeter in resistance mode, measure resistance between the Black/yellow wire terminal inside the CDI harness connector and frame ground. Report back with that measurement. Share this post Link to post Share on other sites
Chesnuts54 15 Posted October 23, 2023 Hey @retro! I got a good voltage reading for the first test(within spec). Then for the second one I got a resistance reading of 1.5 ohms. 1 Share this post Link to post Share on other sites
retro 4,048 Posted October 23, 2023 Ok, both of those measurements are good. Just two more tests though ok...? I still have one of those nagging "what if" questions rattling around in my head. :) Plug everything in, Ignition key on, multimeter set to DC volts mode. Poke your red meter lead under the boot on the Black/yellow wire terminal on the Ignition coil and hold your black meter lead on frame ground while cranking the motor over with the starter. Let me know if you see DC volts measured during the test (and if so the reading). If no DC voltage is seen then you can try tapping on the CDI (pretty sharply, but not so hard that you break it) a few times with a plastic screwdriver handle while you are cranking the motor over with the starter to see if you can get it to make spark intermittently. Share this post Link to post Share on other sites
Chesnuts54 15 Posted October 24, 2023 @retro.. sorry for the delayed response! I’m going to be home shortly to try this out, it’s been a busy week so far! I also wanted to bring something to your attention. I found something unplugged but I’m not sure what it is and I can’t find the wire colors on the diagram. Maybe I am over looking it I don’t know lol I’ll attach a picture. Wire colors are green/yellow and black/brown. Share this post Link to post Share on other sites
retro 4,048 Posted October 24, 2023 2 hours ago, Chesnuts54 said: I found something unplugged but I’m not sure what it is and I can’t find the wire colors on the diagram. That unplugged connector looks like the carburetor heater connector? I can't tell the location where you took that photo but if it is located to the right of the carb area then it is the carb heater plug. It plugs into a connector that clips to the frame on the right side where a few other connectors clip to the frame. The same place on the frame where the (clean & shiny now) main negative ground cable is bolted down. The two-wheel drive, manual shift (TM models) Ranchers have an Air temp sensor connector located at the right/front area not far from the CDI. So it would not be used on your Rancher.... But I don't think that's the one in your photo, your plug is a male half... Share this post Link to post Share on other sites
Chesnuts54 15 Posted October 24, 2023 Yeah I’m not 100% sure what it is! I will have to further inspect. But I’m also wondering should I go on and try to find a CDI, since we confirmed that we’re not getting any voltage to the coil? I might order a new one just for a piece of mind instead of buying a second hand one that might now work. We also confirmed that my stator should be good? It was pulsating at around 0.230V AC or so. I also done what you told me to do with tapping the stator with a screwdriver and it didn’t work. I tried it with both of the CDI’s that I have. Share this post Link to post Share on other sites
retro 4,048 Posted October 24, 2023 If you remove the air filter box you can see two wires coming from the bottom of the carb float bowl. That short sub-harness is suppose to be plugged into a connector which should be clipped to the frame, as shown in the drawing above. You might have to look for that connector if someone removed it from the frame clip before you got the Rancher. Yeah, all of the evidence you've gathered (wiring, CDI connector and power supply are good, pulse generator is good, grounds are good) points to a bad CDI (No primary voltage). You can buy new OEM or used OEM.... the CDI part number for your Rancher is 30400-HN5-305. Here is a used one at Powersportsnation for $59.99 (plus tax) shipped. Warranty is 30 days and they stand behind their parts. https://www.powersportsnation.com/honda-rancher-350-fm-04-cdi-ecu-ecm-box-30400-hn5-305-43243.html RockymountainATV is a good source for New OEM, their price for the 30400-HN5-305 CDI is $212.63 (plus tax) shipped. Start here to browse to the Wiring Harness section for your Rancher where you'll find your part number (#2 on the parts fiche). https://www.rockymountainatvmc.com/oem-parts/Honda Let us know how it goes. FYI, We're having a 2000th registered member ATV contest.... drop a photo of your Rancher into the thread (linked from the banner at the top of the forum) along with a list of mods/accessories for a chance to win some cash! 1 Share this post Link to post Share on other sites
retro 4,048 Posted October 24, 2023 By the way the carb heater does not have to be plugged in. It is there to help prevent icing in the carb and to warm the fuel up slightly (for a smoother idle) in severely cold temps. It's optional.... Share this post Link to post Share on other sites
retro 4,048 Posted October 24, 2023 If your Rancher starts right up after you plug in a new CDI, let it idle while you measure the DC volts charging voltage across the battery terminals with your multimeter. Make sure that the charge voltage is normal and never exceeds 15.5 volts while you rev the motor up. If it does shut the motor off immediately and replace the Regulator/Rectifier. The CDI and/or the ES shift ECM can go up in smoke if the battery voltage ever exceeds 16 volts. Thanks for putting up with all of my long posts.... have fun! :) Share this post Link to post Share on other sites
KrisR 9 Posted October 31, 2023 On 10/19/2023 at 3:59 PM, Chesnuts54 said: Hello there, I’m back at it again. So, not to divert attention from what steps and advice you have give me me but I’m curious about something. So yesterday I followed these steps in the image that retro had listed and I noticed that when I put my leads on the green/white wire and ground the black lead on the frame with the ignition on I don’t get a voltage reading but the other steps I got the correct voltage readings. Any advice on that? Thanks again! Good evening. Thank you for the help. Long time reader. I am posting for the first time. I am not getting 12.6. I am getting 3.7 on Green and white and ground. Any thoughts on that? Share this post Link to post Share on other sites
Fishfiles 20,145 Posted October 31, 2023 6 hours ago, KrisR said: Good evening. Thank you for the help. Long time reader. I am posting for the first time. I am not getting 12.6. I am getting 3.7 on Green and white and ground. Any thoughts on that? Hi Kris' , it would serve you and everyone going forward better to start your own thread and list what year and model ATV you have Share this post Link to post Share on other sites
Chesnuts54 15 Posted November 2, 2023 On 10/24/2023 at 6:50 PM, retro said: If your Rancher starts right up after you plug in a new CDI, let it idle while you measure the DC volts charging voltage across the battery terminals with your multimeter. Make sure that the charge voltage is normal and never exceeds 15.5 volts while you rev the motor up. If it does shut the motor off immediately and replace the Regulator/Rectifier. The CDI and/or the ES shift ECM can go up in smoke if the battery voltage ever exceeds 16 volts. Thanks for putting up with all of my long posts.... have fun! 🙂 Hey there , I stepped away for a bit while I was waiting on a new cdi to come in the mail, thanks for all the help prior 🙂 . I bought a used CDI again this is the second one and my atv still does not start lol it’s safe to say that the CDI is not the problem. However I have another question. If the diode is bad in my fuse box would that prevent spark aswell? I tested continuity on my diode and I couldn’t get anything. If the diode is good then you’re only supposed to get continuity in 1 direction but I’m not sure what it means if there’s no continuity at all. Share this post Link to post Share on other sites
retro 4,048 Posted November 2, 2023 Oh man, I'm sorry! Let me know how much you paid for that used CDI please, I want to reimburse to you your cost. My diagnosis was wrong. It sucks, but it happens sometimes. The diode should conduct current in one direction of flow but not the other, so you are right that it has failed apparently. It is there to prevent flyback voltage from the solenoid windings from reaching the CDI and the shift ECM when the starter button is released. It should not affect the ignition simply by being bad, but replace it just in case I am wrong again. :) Share this post Link to post Share on other sites
Chesnuts54 15 Posted November 2, 2023 It’s all good man! It happens .. I’m sure I can resell one of them. No hard feelings. At least we now know that it’s not the issue. I will replace the diode for sure. Is there anything else I’m missing? I’m just trying to figure out what things I could possibly be looking over. It’s a good idea for me to make a check list and start diagnosing again. So I think we have power going to the CDI but nothing coming out correct?(based off everything we’ve went over). Share this post Link to post Share on other sites
retro 4,048 Posted November 2, 2023 Yeah we didn't have voltage production coming from the CDI to energize the primary winding of the ignition coil. Everything else in the ignition checked out good. So far I don't see anything that we may have missed except for the diode that you found bad. Never doubt that I may have screwed up somewhere though. Lets see what a replacement diode does for the issue. I seriously want to pay for that CDI though. If you'll PM me your cost along with your mailing address I'll be tickled to send you a money order. Or I can Paypal ya if you have Paypal. 1 Share this post Link to post Share on other sites
Chesnuts54 15 Posted November 2, 2023 @retro.. WE HAVE SPARK, I REPEAT… WE HAVE SPARK. It was the cdi.. I accidentally left the stator unplugged from the last time I was out going over things! I apologize for making you feel like your diagnostic skills were wrong! I went out noticed the problem, plugged it back in and away she went! Thank you so much and everyone else who stopped in to try and give some advice! Cheers🍻 2 Share this post Link to post Share on other sites
retro 4,048 Posted November 2, 2023 Hey let's celebrate!!!! Awesome work! Don't forget to measure the charging voltage going into the battery while revving the motor up, just to make sure that your used Regulator/Rectifier is a good one..... Man we needed this one bad! Thanks for putting up with my lengthy posts, you're awesome! We like to see pics by the way..... :) 2 Share this post Link to post Share on other sites
