Honda NX650 Dominator '92

Wanted to try a big single... So after a bit of searching came across this... It was local, had MOT & tax & went for a reasonable price...

All seemed well for a couple of weeks then it started to hesitate as if it was needing to be switched onto reserve...

Further investigation narrowed the symptoms. It will rev to 4,500 rpm then, if the throttle is held, the revs will drop back to around 4,000, then hover between the two figures...

Unaware of its history in any great detail, we checked the obvious fuel line potential issues, all ok. We when removed, dismantled & cleaned the carb in our ultrasonic cleaner. We noticed the emulsion tube was distorted, it looked as if it had been drastically over-tightened at some point, but figuring that this couldn't have just happened the carb was re-assembled & replaced.... No difference... 

The carb to cylinder head connector on these is made from rubber & prone to splitting underneath... This one had started to split but it didn't look like it had gone right through, but would be something to keep an eye on.

Choke ok.

Air box opened, the only difference being that it revs around 500 rpm higher

Having drawn a blank with fuelling, attention was turned to the ignition system.... All the coil resistances (ignition, HT & LT, & pick-up trigger coil) were within the tolerance bands given in the manual I downloaded... This pointed to the CDI unit being at fault... A used one was bought & tried... No difference...

Carb is going to be cleaned again now & the emulsion tube renewed...