Rough Sounding Engine

[Pablo]

I have a brand new 2008 FJR1300A. I've had it since January, and I currently have around 1,400 miles on the odometer. Recently I've started to hear a rough thumping sound upon starting a cold engine that ceases after about thirty seconds or so. I don't seem to remember ever hearing this noise before. And I have had its 600 mile initial preventive maintenance taken care of. What gives?

 

[FJRBluesman]

???

Need more information. Is the thumping in time to the engine revolutions? Is it faster or slower than the engine revolutions? does it sound metallic? Does it sound hollow? Does the noise slowly go away or suddenly? etc....

Maybe you need to take it in if sounds real bad. You don't want to damage anything any further if there is something wrong.

 

[Pablo]

???
Need more information. Is the thumping in time to the engine revolutions? Is it faster or slower than the engine revolutions? does it sound metallic? Does it sound hollow? Does the noise slowly go away or suddenly? etc....

Maybe you need to take it in if sounds real bad. You don't want to damage anything any further if there is something wrong.

No, the thumping, or clunking sounds, aren't in time with the engine revolutions and they're not very loud. They seem pretty sporadic, and they cease once the engine begins to warm. It only seems to happen while starting a cold engine.

 

[FJRBluesman]

Just a thought...I'm grasping at straws here since I don't own a 2008, and I can't here it etc, but.... How is your clutch when you engage/disengage it? I'm wondering if the clutch basket is making noise due to the plates sticking then breaking loose and clunking the basket when they free up, with some lubrication and warmth as the engine heats up.

EDIT***

Also is the engine idling smoothly when you hear it? I'm also thinking if it has a slight dip in the idle for a plait second (like pulsing) and it could be making some sound as it suddenly increases a 100rpm or so...???

 

[ionbeam]

During initial cold start, the Air Injection System is active. The ECU commands a solenoid to open an air path between the intake air box and 4 reed valves, one reed for each cylinder which inducts fresh air directly into the exhaust stream. The air induces a secondary burn of any HC’s left over from cold enrichment combustion. If you lightly rev the engine when the reed valves are active you can hear popping in the exhaust pipes. The solenoid opens the air path until the coolant comes up to operating temperature, then the ECU shuts off the solenoid. Once the engine is up to operating temperature the AI system will only be active when you are at idle. The solenoid is simply turned on/off, no pulsing, no modulation. The solenoid is open when there is no voltage at the solenoid’s coil, it takes +12 volts at the solenoid coil to shut it off. Unplugging the AI solenoid will cause it to be open all the time.

Maybe this is what you are hearing?