Hello Dave,
Since I bought used in 2018 my CB1100 '13 with less than 8.000 miles, it suffered some issues related to the idle.
During the first period it had a idle instability with 1.800 rpm, solved during the warranty period (mandatory in Italy when you buy an used vehicle from a dealer) with the cleaning of the IACV and soft reset of the ECU errors.
After in the following year, bike started to have sporadic problems to the idle, 600 rpm, in different situations, hot weather, stop and go traffic, long mountain descents, cold weather. I did a diagnostic in the Honda dealer before the warranty expired, but no errors were found in the ECU. They told me that similar problems occurred in bikes with last pollution requirements. Since then I started my investigations to understand the cause of the problem not only on my bike but on what experienced from others. How you already know, this problem is common for a lot a CBs produced since 2010 to 2016, also if less in the period from 2014 to 2016. No reports for the last models produced since 2017. I started considering how and which values ECU reads from different sensors, so I learned that it reads also analogic values (volts rather than ON/OFF values). So I started to analyse which could be the consequences of the battery voltage on the behaviour of the bike. You have to consider that the main headlight has a power consumption of 55 W constantly, also if you are running in the traffic at low rpm with less charge from the generator. I found that starting a ride with a completely charged battery, the idle instability problem was reduced, but not disappeared particularly with hot weather, so I think to problems related with the hot temperature of the engine (checking on the while if in the world someone was able to find the solution...). To low the engine temperature I decided to install a modified IAT sensor to have a different Air/fuel ratio. Compared with other CBs the hot from the engine is effectively lower. The idle instability with hot weather disappeared, but remained with long hill descents. I reduced the power consumption of the battery, installing a LED H4 lamp on main headlight, but not sorting positive effects. Until this year I lived with the problem but able to live with it understanding when it have could appeared and able to solve it, switching of and on the engine on run, and basically rarely. Also I reported everything to the other dealers in the area asking for a solution, without any kind of reply. Since of the end of last year, I started to read in the web some good news about the availability of an updated ECU software in some countries (Germany, Austria) solving the idle instability. Since than I started to contact Honda dealer to know the availability of the updated software without positive reply. And as I wrote, after requesting to connect the bike to the factory PC, Honda mechanic was able to find the update. No comments about the update by Honda, on the PC only appeared the available (and suggested) update software for the CB. They weren't able to explain the reason for which they never received an alert about it. It seems that the update has been released in 2025 , no more info. Unbelievable from a company like Honda, but it is so. Anyway I did the update in July, since then no problems
. I hope it's clear now.
