91 Cb750 Gremlins ... Thinkin ICM ... Thoughts

I ll make this quick , bought a project 91 CB750 (15000 miles All stock) , bought it with the carbs in pieces in a tray , seller bought it like this from somebody else ... Anyway , like a blind squirrel with a service manual , I got it back running but its not good . Its running lean and popping out the right side exhaust like mad and as it warms up it just starts to fight staying running and misfiring ... Okay from the top ... I went thru the carbs and they where very clean inside , its not my first rodeo on motorcycle carbs , these are very similiar to my goldwing carbs ... All passages clear , diaphragms look super and it has the correct jets for the year , I see no problems with them .... When I had it running , i sprayed starting fluid on all the carbs , and intakes , there are no intake leaks of any sort . I drained the bowls and measured the gas amount in every bowl and they were darn near perfect . Away from the carbs , checked compression , 150 psi every cylinder , I checked all the ohms reading for the two coils and the pulse generator from the cdi plug as per manual , they all spec good within the range and there are no broken wires . I double checked the coils directly and they are in spec . I even swapped them and there was no change , still popping out the right pipe , and running terrible . One would think its a carb issue , but I never heard a bad carb make a bike run so poorly . I havent changed the plugs yet , but I have swapped them around and changed nothing . My only ray of light is the ICM or the Pulse generator , anybody seen a bad ICM or pulse act up on this bike .... Not sure what to think at this point

Yikes. I have no experience with 90s nighthawks, but assuming your carbs are completely clean, you might have to sync them up.

Hello , thanks for the reply , carbs are synced the best I can right at the moment , I just removed the valve cover to check the timing and its spot on , the motor is very clean inside ... Side note , I realize its not a cdi persay but a ICM module , completely different animal

Poor carb sync can cause symptoms similar to vacuum leaks, poor fuel delivery, and electrical issues. Best to do that to narrow down troubleshooting.

I Thought I would follow up on this post so that somebody else my learn something ... After messing around with the bike , I found two problems that I got lazy with after checking so many connectors and wiring and so on ... First off , I had a bad plug cap that the screw that the wire feeds into came out with the wire when I unscrewed it ... I ohmed all the caps thru the coils , one of the first things I did , and they were fine but I guess one was bad and if I would of unscewed the cap , I would of noticed sooner ... honest mistake ... but aggravating none the less ... Also I had pretty good voltage drop at the coils , and of course , I took for granted that every connector I looked at was very clean so I again got lazy and didnt check every one of them ... Sure enough , the plug in the headlight bucket for the ignition switch was green and crusty , all the other connectors in the headlight bucket were very clean and interesting enough , the terminal ends for the ignition switch were of a diffrent type metal( Silver) than all the other connectors (Brass) and they are prone to corrosion more than the others , it was all stock Honda plugs btw ... Lesson learned , you have to check EVERYTHING ... Bike runs great now with the original ICM and pulse generator that were not the problem . Hope this helps others here ... Good Day Gents

Great follow up! Rare to see people come back after their issue is resolved and detail it that well. Thanks.

elektrikery , strange stuff .