Peka Posted November 27, 2020 Share Posted November 27, 2020 Hello fellow riders, I've been trying to months to resolve issue with no power in high rpm on my RC36 VFR 750 1990. Issue is not related to carbs and whole air/fuel system, since all that was serviced. It seems that is electrical problem. I found out that one spark plug cap was giving 1000+ kOms, so I replaced that. Also I've been measuring all electrical installations, and found that I don't get good measuring on pickup. According to instruction, when I measure resistance on 4P mini connector between yellow and white/yellow I should get between 200 - 400 Oms, but when I measure resistance between yellow and white/blue I don't get nothing. Also, when I measure on the ICM side resistance between yellow - white/yellow and yellow - white/blue manual says that I should get 450 - 500 Oms, but I get around 290 Oms. So to recap: ICM side measurement: Yellow - White/Yellow 290 (450-500 according to manual) Yellow - White/Blue 290 (450-500 according to manual) 4p mini black connector Yellow - White/Yellow 290 (200-400 according to manual) Yellow - White/Blue 0 (450-500 according to manual) I'm wondering if I'm measuring resistance on right way. Can anyone explain me how to properly do that? Thank you in advance! Daniel Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted November 27, 2020 Member Contributer Share Posted November 27, 2020 Hi Daniel. The procedure for checking the Ignition Pulse Generators in the manual has a typo error. Its states to measure between the Yellow and the White/Blue this is incorrect. Should be Blue to White/Blue. 200 to 400 ohms. And the other is the Yellow to White/Yellow. Again 200 to 400 ohms. Refer to drawing attached. Hope this helps Cheers. Link to comment Share on other sites More sharing options...
Peka Posted November 27, 2020 Author Share Posted November 27, 2020 Hi Grum! Thank you for this note! I will measure tomorrow, to see will it be any difference. Link to comment Share on other sites More sharing options...
Member Contributer DannoXYZ Posted November 28, 2020 Member Contributer Share Posted November 28, 2020 6 hours ago, Peka said: Issue is not related to carbs and whole air/fuel system, since all that was serviced. Don't rule out carbs just because you had them "serviced". It really depends upon quality of work and skill by person doing them. Requires lots of scrubbing, ultrasonic soaking and micro soda-blasting. When I got my Ninja 250 race-bike from retiring AFM-racer, I figured I'd send to dealer for "servicing" of carbs. Nothing... Then 3-days later, I get call from service-tech asking where they can find OBD port to connect diagnostic scanner!! Hahahhahaha!! I ended up sending them to Gordon (ducatiman) in NY for restoration as he's only one I've found that can do expert job on carbs. Also did you rebuild petcock? Measure its opening vacuum and flow-volume? Link to comment Share on other sites More sharing options...
Peka Posted December 2, 2020 Author Share Posted December 2, 2020 On 11/27/2020 at 10:31 PM, Grum said: Should be Blue to White/Blue. 200 to 400 ohms. And the other is the Yellow to White/Yellow. Again 200 to 400 ohms. I measured according to this, and it is fine. But when I measure on back side, on ICM side, it is also around 290 oms, instead 450 - 550 oms, according to manual. Should that concerning? Link to comment Share on other sites More sharing options...
Peka Posted December 2, 2020 Author Share Posted December 2, 2020 On 11/28/2020 at 2:49 AM, DannoXYZ said: Measure its opening vacuum and flow-volume? Thank you for this suggestion, can I ask how to do this? Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted December 2, 2020 Member Contributer Share Posted December 2, 2020 3 hours ago, Peka said: I measured according to this, and it is fine. But when I measure on back side, on ICM side, it is also around 290 oms, instead 450 - 550 oms, according to manual. Should that concerning? Are you measuring this with 4p plug still connected to the Pulse Gen Coils? This would explain your reading of 290 ohms. From what I read, the coils need to be unplugged for this test, you are measuring the resistance of wires Yellow (common) to White/Yellow and Yellow (common) to White/Blue. This is a measurement of the ICM internal resistance to these wires and you should have between 450 - 550 ohms for the two readings. You have already confirmed both the Ignition Pulse Coil resistances are correct, and with the coils still connected it would be impossible to read 450 - 550 ohms in the above test unless they were unplugged to then measure resistance on the wires back to the ICM. Hope this helps, also I don't have a 4gen. Just going by the circuit diagram and the test procedures! Good luck. Link to comment Share on other sites More sharing options...
Peka Posted December 12, 2020 Author Share Posted December 12, 2020 On 12/2/2020 at 10:25 AM, Grum said: Are you measuring this with 4p plug still connected to the Pulse Gen Coils? This would explain your reading of 290 ohms. From what I read, the coils need to be unplugged for this test, you are measuring the resistance of wires Yellow (common) to White/Yellow and Yellow (common) to White/Blue. This is a measurement of the ICM internal resistance to these wires and you should have between 450 - 550 ohms for the two readings. You have already confirmed both the Ignition Pulse Coil resistances are correct, and with the coils still connected it would be impossible to read 450 - 550 ohms in the above test unless they were unplugged to then measure resistance on the wires back to the ICM. Hope this helps, also I don't have a 4gen. Just going by the circuit diagram and the test procedures! Good luck. I tried to measure on ICM side. So I unplugged coils, and unplugged 4p pulse gen connector. Measured on ICM side, but I didn't get any results. Do I need to turn key ignition on ON (II) position while I measure? Or crank the engine? Since I don't get any readings when I measure? Either ICM is broke 😄 Link to comment Share on other sites More sharing options...
Member Contributer Grum Posted December 12, 2020 Member Contributer Share Posted December 12, 2020 Ok then perhaps the stated reading of 450 - 550 ohms. Is also a typo error and this test is just confirming the wiring and coil resistances from the ICM connection down to the coils!! Sorry i can't offer more info as I have never owned or worked on a 4th gen. Perhaps any of the 4gen owner members might be able to clarify this for you. Link to comment Share on other sites More sharing options...
Member Contributer DannoXYZ Posted December 13, 2020 Member Contributer Share Posted December 13, 2020 8 hours ago, Peka said: I tried to measure on ICM side. So I unplugged coils, and unplugged 4p pulse gen connector. Measured on ICM side, but I didn't get any results. Do I need to turn key ignition on ON (II) position while I measure? Or crank the engine? Since I don't get any readings when I measure? Either ICM is broke 😄 if you unplug the connector to pickup-coils you can't measure them. The idea is to unplug everything except what you want to measure. And you're measuring terminals at the ICM connector right? Not the ICM itself. Note from diagram, that wire-colours change for pickup coil after connector. Best to do 2-readings, one at pickup-coils themselves and one at ICM connector to verify wiring in between. Better test is to use oscilloscope to test output of pulse triggers at ICM connector. Do you have access to oscilloscope? Link to comment Share on other sites More sharing options...
Peka Posted January 6, 2021 Author Share Posted January 6, 2021 Hello guys! Just to let you know that I fixed the problem! ICM and one sparkplug cap is replaced, and now bike is like new again! Thanks for the help! Link to comment Share on other sites More sharing options...
Member Contributer DannoXYZ Posted January 6, 2021 Member Contributer Share Posted January 6, 2021 Good job! Seems ICM failure is more prevalent than I would expect. Honda must have used same electronics department that was responsible for RR debacle. Link to comment Share on other sites More sharing options...
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