Onan 4.0 unusual noise

Question

I have an Onan 4.0 with 14 running hours in my TH and it is making what I think is an unusual noise since about hour 2.  Shortly after start up it sounds like there is a quick, loud popping sound that runs about the same speed as the rpms?  In the following video you can hear it much better at about the 15 second frame.  Brought it to the dealer months ago and they could not reproduce the sound (go figure)?  Any ideas?  http://smg.photobucket.com/user/tnl/media/Toy%20hauler/genny.mp4.html

the_bear_ii · Answer

Never heard the sound in the video...I watched it several times, sounds normal all the way through the video.

2500_grunt · Answer

Sounds like a valve ticking or tapping??  Coming from the area of the solenoid (?) or where the ele. lines come thru the grommet and connect to the terminals on the solenoid looking part?

wayne_dohnal · Answer

I'm assuming from your signature that your generator is fairly new, so this info probably doesn't apply.  In the ~2008-2009 ballpark Onan had a batch of bad valve springs for the ky generators, and many of them broke at low run times.  Your 14 hours is right at the sweet spot where these springs broke.  Both of mine failed.  The symptom was that the generator just stopped running.  One spring was broken in multiple places and the other in one place, kinda-sorta still functioning.  It's pretty easy to pull the valve cover and check the springs, and you could check the valve clearance at the same time.

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Onan 4.0 unusual noise

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