The Honda service manual states to hold the engine speed above 3900 rpm to verify if fault code 25 or 26 is triggered. ST1300 owners on this site who do have this defect in their ECM overwhelmingly have reported that as long as they maintain the engine RPM below this threshold the FI light will not illuminate and code 25 or 26 will not be set. If they exceed this threshold the FI light illuminates and code 25 or 26 is set. This would seem to confirm the 3900 RPM threshold requirement for ST1300's that is stipulated in the Honda service manual. I personally always recommend 4,000 RPM or above for no other reason than just to be sure that the engine was run at a high enough RPM to have confidence in the test result while it still meets Honda's requirement of above 3900.
The test criteria in the Honda service manual stipulates to maintain the elevated RPM for 10 seconds or more to verify if fault code 25 or 26 is present. Many people on this site who know that they have this defect have reported that it can often take longer than 10 seconds before their FI light will re-illuminate after clearing the codes. Because of these two factors I always recommend a test of at least 30 continuous seconds for no other reason than an abundance of caution and because there is no good reason not to while attempting to determine if this condition is present.
