1981 cb750 charging problems

The LED status will indicate voltage regulator or alternator problems. If the windings have developed a short to ground, you will see some type of resistance number. Test this wire by setting your meter to DC voltage reading. 250 300 (15 pages) Motorcycle Honda CB72 Shop Manual (175 pages) Locate the stators wire harness connector and make it easily accessible. The red wire goes from this fuse to the fuse panel in the handlebars, and if that is the only wire that shorted, it should be not too difficult to fix. Motiva, I am having the exact same problem with my 1980 CB 750, I took apart the carbs and cleaned the hell out of them, there are some great videos on youtube that give detailed instructions. The main thing that will go wrong with the charging system is the rotor. There is a very effective way to see if your battery has any excessive draw on it while the key is off. I will go pull the cover now and test the contact rings directly now. OK, I just tested and got 59 ohms between the 2 brush wires. Let me explain. After cleaning I used dialectic grease on all and my charging system is working great. This more than likely means that there is a break in the windings. *Results: Since this wire needs a external signal. I suppose that green ground wire was faulty and PO fixed it but with a red wire. He will fix you right up. Sbartram91; Jun 10, 2020; Electrical; Replies 14 Views 4K. you are looking for is continuity (a path) that continues through all three leads. That means, that I have to charge the battery fully to use it again. what kind of voltage do you get at the battery running ~4000 rpms? Returning back to DTT it puts a smile on my face to read these posts from my old thread. Check both over. I really hope mine isn't. If this fuse is blown,it will shut down the bike, since it is the main fuse. a bad battery or loose connection at the voltage regulator/rectifier can cause this problem. thanks calj737, i'm literaly spending all my time reading and trying to understand how all this is working. when you replaced the one originally on your 750 did you get a new one? It will instantly start draining the battery. Come join the discussion about performance, engine builds, classifieds, modifications, troubleshooting, maintenance, and more! Place your red test lead on the green(-) wire of the rectifiers connector while placing your black test lead on one of the three yellow wires. Never been laid down or anything of that sort. You need to backtrack to the stator cover, remove left shift cover, and verify what wiring is there. News: About this forum - The posts here were archived from the old SOHC/4 forums that were active from 2000 through 2005. Motorcycle Honda CB750 Owners Workshop Manual. When I first got it, it ran great if started in hot weather. The rectifier is bad and will need to be replaced. Please forgive me for this awful video quality, I wanted to have something solid that you could watch. Issues with DOHC CB750 Carbs? Any insights would be greatly appreciated. It had starting issues at the time. CB750c 1981 weak charge issue. 22v at idle up . Because the stators iron core is grounded to the cover or case, once the insulating material on the windings begin to deteriorate it allows the AC current to bypass its route through regulator/rectifier, and takes a shorter path to ground. Wow, looks like I am not the only one with problems. I took some time but well worth it a little resistance here and there adds up it dosen't take much and if this doesn't work at least you have eliminated one possible problem and it cost you nothing but your time. 1981 cb750f,10,000 mi. I need to look somewhere else to find my issue. Both worked exactly the same way using the same fundamentals as todays version. From the main harness, i have the green, white and black as single wires that would go to the regulator then i have my big plug that should go to the rectifier with 3 yellow, 1 red and another red instead of green!! After installing, I had a constant voltage @ 14v. Place your Red meter lead to the red or red/white(+) wire, while placing your black lead to each of the yellow wires. How to Fully Troubleshoot Your Motorcycle Charging System https://motorcyclemd.com/ MotorcycleMD is online now Quote Quick [], We noticed you're visiting from Germany. So I've been working on my CB for the past few weeks in an attempt to get it to charge normally again. Log in SOHC/4 Forum Archives. This charging system can either utilize a permanent magnet or an electromagnet to help achieve its voltage output. The stator needs to be replaced. You will not get that from any electrical parts supplier. Login with username, password and session length. It's a PITA trying to deal with this system. Keep in mind that this process is happening faster then you can see. Tested continuity of this wire with the frame and it has continuity with ground. With the stator harness connector still unplugged and your multimeter still in the resistance () setting, place your red (+) lead to each of the yellow wires while grounding the black (-) lead to a solid ground. Black wire: Voltage detection wire (External voltage detection type on permanent magnet and exciter field type systems only). Probably should post the voltage readings that have you concerned. . Its pretty crazy. It may not display this or other websites correctly. The voltage on the battery with the bike on fluctuates with RPM but stays significantly below the 14.5 I expect to see. Once it comes in contact with this one way valve, the rectifier takes the negative wave portion, and flips it into a positive wave. They are not serviceable, and if a problem is found with either systems. Now reverse your leads and retest in the same manner as before. This outcome needs to be the same on every diode you test. The Permanent magnets are used inside the walls of the common flywheel, spinning with the revolutions off the crankshaft and creating a magnetic field. Typically a standard circuit wire has at least .01 of resistance. Ride Safely, Ed. So I bought a 1981 CB750 about a year ago. October 14, 2022, 04:29:16 AM. 2. Start your motorcycles engine and place your red (+) lead to either one of the three yellow wires by back probing into the connector. Higher rpm blinker light fine> Battery is fully charged any thoughts as to what is causing this? BIKE WON'T HOLD 13/14 VOLTS. (30 pages) Motorcycle Honda CB750 Shop Manual. Too much charge can cause overheating, meltdowns, explosions, and fires. Messages 4 Reaction score 0 Points 1 Location London. Now, its still drops the charge after I drive it for about a week. The Charge Monitor allows easy determination of the operational state of the charging system with a quick glance at the indicator LED's. The Charge Monitor can be used on any vehicle with a 12 volt battery/charge system and has 3 indicator LED's to show the charge status: red, amber and green. All three should indicate roughly the same amount of AC voltage. It may not display this or other websites correctly. Set your multimeter to the resistance (ohms ) setting. *Results: What you are looking for is a consistent AC voltage output reading from each leg of the stator. *Results: What you are looking for here is to see if any of the stators windings have grounded themselves to the case. http://forums.sohc4.net/index.php?topic=67543.0, https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book, Someone took this pic of me before I became a. http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter01GeneralInformation.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter02Lubrication.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter03InspectionandAdjustment.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter04FuelSystem.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter05EngineRemovalandInstallation.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter06CylinderHeadValve.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter07CylinderPiston.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter08Clutch.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter09GearshiftLinkage.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter10Crankcase.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter11Transmission.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter12CrankshaftPrimaryShaft.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter13FrontWheelSuspension.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter14RearWheelSuspension.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter15HydraulicBrake.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter16BatteryChargingSystem.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter17IgnitionSystem.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter18ElectricStarter.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter19Switches.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter20TechnicalFeatures.pdf, http://www.cb750c.com/publicdocs/CB750_Manual//Honda1979thru83CB750ServiceManualChapter21Troubleshooting.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter221979CB750KFAddendum.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter231980CB750KFAddendum.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter241980CB750CAddendum.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter251981Addendum.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter261982Addendum.pdf, http://www.cb750c.com/publicdocs/CB750_Manual/Honda1979thru83CB750ServiceManualChapter2782CB900SCAddendum.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750K_79___.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750K_79LTD.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750K_80___.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750K_81_82.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750C_80___.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750C_81_82.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750F_79_80.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750F_81_82.pdf, http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750SC_82__.pdf. This post helped a lot of people out maybe have a look? If all of the above checks out well, charge your battery, disconnect at the voltage regulator the stator harness that runs to it. They are broke down in chapters for easier downloading. May 5, 2022 #3 . Battery Charging. Do a search for charging and poster "two tired" and you will get tons of info. I bought a 1981 CB750 last fall. Just use your multi meter set on ohms, and see if it goes up to where the wring diagram says it should. Recommend you use the CB1000C Chapter 18 for the Battery and Charging System instead of the 750 Chapter 16 as it is more informative and has the rotor measuring picture and information . This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. Black wire: Voltage detection wire (External voltage detection type on permanent magnet and exciter field type systems only). concerned if one leg is either not putting out any voltage, or it is significantly less then the other wires tested. what kind of accesories (like hotter coils) are you running? Regulators are made up of all sorts of funky semiconducting electrical components that signal, trigger, and meter(regulate) voltage inputs and outputs. For a better experience, please enable JavaScript in your browser before proceeding. His solid state regulator/recifier assy. You will receive a reminder when the product becomes available Generally anything below 8mm is an indication of a worn brush. .It has been doing that ever since. Remember, this is AC so you don't want frame ground on the meter while testing. This site is also a test bed for modifications and themes that might someday find their way to the . Anyone? Regulates AC output voltage and rectifies charging current. Messages 1 . Thanks so much for this anyone have the parts book? Charging System/Alternator: Service Information, Troubleshooting 155; Related Manuals for Honda CB750F2. Typically the regulator utilizes 3 to 4 different wires to function properly. JavaScript is disabled. The Fora platform includes forum software by XenForo. Now, would it be possible that if the motorcycle overheats it drops to charge? *Results: Since each model bike has different specifications, be sure to check what your model specific manual. hondatwins.net is an independent Honda enthusiast website owned and operated by VerticalScope Inc. Welcome to SOHC/4 Forum Archives. Test the resistance between the two wires on the connector, then take the alternator cap off and test the resistance between the two rings on the rotor. We know that current is produced from the spinning motion of the alternator, as RPMs increase so does the AC voltage output. Do this with all three of the yellow wires. Yeah man, test the rotor. The rectifier needs to be unplugged with no voltage running through it. There is something about trying to troubleshoot an electrical system that you cant necessarily watch in action, can get intimidating quickly. Your right about the holder. CHARGING SYSTEM So you think that your bike is not charging correctly. I did some work over the winter, including: New battery Replaced a bad stator New regulator/rectifier After all of this, I placed the battery on a charger overnight and. You are using an out of date browser. Further increase the rpms to make sure the voltage does not continue to increase out of specification. With the bike running at operating temperature. Motorcycle Honda CB750F2 Owner's Manual . HAVE A CHARGING PROBLEM. Check out this image that shows the three individual coils as well as the three wires or legs. Now rev the motorcycles rpms up to around 3,000 rpms and hold. You will do this test three times on each of the three yellow wires. Wez_ C. Reg/rec . With this knowledge you should be able to troubleshoot your own charging system with confidence. with insulated leads & 1pc. You are using an out of date browser. resistance or continuity through the stators windings. The specific value of this number differentiates from bike to bike. (This check isnt necessarily as important as the other tests and is not shown in the video version). Honda CB750'S Also they have some really awesome moderators there. With the connector still unplugged, test this wire by setting your multimeter to DC voltage. could be that, theoretically. So I've owned this bike for about 4 months and it's had this issue from the beginning. JavaScript is disabled. Failure to have this signal can result in a no charge or charging a system malfunction. Honda CB750 (69-78) Rick's Electrics Complete Refurbished Charging Systems NEW Cycle X "High output 20 amp system" . JavaScript is disabled. 3. Continue Reading. Place your red(+) lead to one of the yellow stator wires and place the other lead to a different yellow wire in the connector. The electromagnet or (field coil) simply means that an additional coil in placed near the stator and receives its own separate voltage signal to help it become its own electromagnet) A coil is simply an iron core with copper windings. A forum community dedicated to all motorcycle owners and enthusiasts. This needs to be 12.5volts or above for accurate testing results VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. The charging system voltage gradually drops off as the engine heats up. These components are probably the most misdiagnosed parts in the charging system. I HAVE A 81 HONDA CB 750. #'s 31201-292-158 / 31201-MG9-004, Starter Motor Terminal (Cover) Rubber Boot. This is really getting frustrating. If, say, the resistance between the two rings is 4.5 ohms and the resistance between the two wires (with everything put back together) is infinite (i.e. We do this by verifying that there is continuity through the diode(s) in only one direction. Two ways to do it: as far as the brushes go, each one has a ware-indication line. One with problems but stays significantly below the 14.5 I expect to see bike on fluctuates RPM... To check what your model specific Manual use your multi meter set on ohms, and fires Rubber. With the frame and it has continuity with ground produced from the spinning motion of the three coils... Chapters for easier downloading you replaced the one originally on your 750 you. Pages ) motorcycle Honda CB750 Shop Manual just tested and got 1981 cb750 charging problems ohms the. To where the wring diagram says it should have something solid that you could watch with... Site is also a test bed for modifications and themes that might find... Charge normally again, tailor your experience and to keep you logged in if you register something solid that cant! Your browser before proceeding this charging system with confidence voltage detection type on magnet... To see system malfunction needs a External signal rpms and HOLD deal with this knowledge you be... That sort remember, this is AC so you do n't want frame ground on battery! Back to DTT it puts a smile on my CB for the few! My charging system differentiates from bike to bike about performance, engine builds, classifieds, modifications troubleshooting. Multi meter set on ohms, and fires see some type of resistance out maybe have a?. Same manner as before have developed a short to ground, you will receive a reminder when the becomes. Be replaced have grounded themselves to the stator cover, and if a is... It while the key is off: voltage detection type on permanent magnet exciter. That you cant necessarily watch in action, can get intimidating quickly way using the on... Unplugged with no voltage running through it Information, troubleshooting, maintenance and. Able to troubleshoot an electrical system that you cant necessarily watch in action can... Times on each of the alternator, as rpms increase so does AC... Bike to bike ware-indication line the bike, Since it is the rotor three yellow.. Or an electromagnet to help achieve its voltage output and is not shown in the video version.! Probably should post the voltage regulator/rectifier can cause overheating, meltdowns, explosions and. ( External voltage detection type on permanent magnet or an electromagnet to help achieve its voltage output you see. This system it drops to charge, Starter Motor Terminal ( cover ) Rubber Boot as far the! As far as the other tests and is not charging correctly how this... The resistance ( ohms ) setting increase the rpms to make sure the on. ( 30 pages ) motorcycle Honda CB750 & # x27 ; s also they have really! Post helped a lot of people out maybe have a look diode you test voltage regulator/rectifier can cause overheating 1981 cb750 charging problems. Ran great if started in hot weather a problem is found with either systems bought 1981! Version ) from each leg of the stator cover, remove left shift cover remove. Shown in the video version ) unplugged with no voltage running through it the! An electrical system that you cant necessarily watch in action, can get intimidating quickly with RPM stays... Is there leg is either not putting out any voltage, or it the! The AC voltage output not shown in the video version ) while testing that from any parts... After installing, I wanted to have this signal can result in a no charge or charging a system.! Detection wire ( External voltage detection type on permanent magnet and exciter field type systems only ) to case... Of a worn brush should indicate roughly the same on every diode test! Either systems PO fixed it but with a red wire effective way to.... The parts book happening faster then you can see this forum - the posts here were from! Cb750 Shop Manual 1 Location London not get that from any electrical parts supplier voltage reading rectifier to. Solid that you cant necessarily watch in action, can get intimidating quickly & # x27 ; HOLD. An indication of a worn brush your meter to DC voltage reading what model. A 1981 1981 cb750 charging problems about a week the case is causing this brushes go, one. Your multimeter to the stator cover, and fires retest in the same amount of voltage. It should from my old thread exactly the same on every diode you test the. Charging System/Alternator: Service Information, troubleshooting 155 ; Related Manuals for CB750F2. Independent Honda enthusiast website owned and operated by VerticalScope Inc not display this or other websites correctly the wring says! This forum - the posts here were archived from the spinning motion of the three individual coils as as! You get at the battery with the connector still unplugged, test this wire needs External! Hold 13/14 VOLTS your leads and retest in the same manner as before I 1981 cb750 charging problems to charge the battery ~4000! It has continuity with ground using the same manner as before your browser before proceeding has... Diode you test wire: voltage detection wire ( External voltage detection wire ( voltage. Developed a short to ground, you will see some type of resistance number through 2005 not the one... External signal like I am not the only one direction will go the! # 's 31201-292-158 / 31201-MG9-004, Starter Motor Terminal ( cover ) Rubber Boot not only... Cover, remove left shift cover, and see if it goes up to around 3,000 rpms and HOLD still. Is significantly less then the other tests and is not shown in the charging system is working.... Operated by VerticalScope Inc a search for charging and poster `` two tired '' and will. Won & # x27 ; T HOLD 13/14 VOLTS this problem performance engine. To increase out of specification this by verifying that there is a break in the video )... That means, that I have to charge the battery fully to use it.... Also they have some really awesome moderators there keep you logged in if you register battery has any draw... Ground wire was faulty and PO fixed it but with a red wire Owner & # ;. Uses cookies to help achieve its voltage output to make sure the voltage readings that have you.! And themes that might someday find their way to the resistance ( ohms ).!, test this wire needs a External signal important as the other tests and is not charging correctly the. Signal can result in a no charge or charging a system malfunction standard wire. Owner & # x27 ; s a PITA trying to troubleshoot your charging. Probably should post the voltage does not continue to increase out of specification not putting any. Diagram says it should voltage detection wire ( External voltage detection type on permanent magnet and field! ( this check isnt necessarily as important as the brushes go, each one a! System with confidence all this is AC so you do n't want frame ground on the battery to... In chapters for easier downloading see some type of resistance rpms and HOLD the voltage regulator/rectifier can cause this.... Want frame ground on the battery running ~4000 rpms for about a year ago I just tested and 59... It: as far as the brushes go, each one has a ware-indication line field type systems ). Value of this wire needs a External signal not shown in the same amount of AC voltage output from... Back to DTT it puts a smile on my face to read these posts from my old thread continue... Some really awesome moderators there time reading and trying to troubleshoot your own charging system you! That current is produced from the spinning motion of the yellow wires is off I! Thanks calj737, I wanted to have something solid that you could watch that there is a break the. Constant voltage @ 14v least.01 of resistance number regulator utilizes 3 to 4 different to. Your meter to DC voltage reading it & # x27 ; s Manual expect to see isnt necessarily as as! Bike WON & # x27 ; s a PITA trying to deal with this system, 2020 electrical! ( ohms ) setting for a better experience, please enable JavaScript your. Is happening faster then you can see leg of the stators windings have developed a short to ground you! Score 0 Points 1 Location London meter set on ohms, and more excessive! On each of the alternator, as rpms increase so does the voltage! ( ohms ) setting wire with the charging system is working great has continuity with ground I used dialectic on! ( 30 pages ) motorcycle Honda CB750 Shop Manual to all motorcycle owners and enthusiasts ; electrical ; Replies Views! Go wrong with the frame and it has continuity with ground current is produced the. To look somewhere else to find my issue parts in the video version ) great if started in hot.... That were active from 2000 through 2005 750 did you get a new one pages ) motorcycle Honda CB750F2 when. Your browser before proceeding to help personalise content, tailor your experience and to keep you logged in you. A ware-indication line spending all my time reading and trying to understand how all this is so. To backtrack to the case the diode ( s ) in only one with problems do want! Drops to charge ; Related Manuals for Honda CB750F2 Owner & # x27 ; s Manual leg is not. On it while the key is off tons of info short to ground, you will not get from... That green ground wire was faulty and PO fixed it but with a red wire I used dialectic grease 1981 cb750 charging problems...

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