Engine noise suddenly disappeared....?

My current commuter 750 has always had a certain engine noise, ever since I got it two years ago. The noise is a bit of a diesel-like sound, not loud and really only there at low rpm and under initial acceleration .

I figured it's just a valve with excessive clearance (I intend to check the valves this winter), because I checked the camchain tensioner and it was well-adjusted. In fact, the whole bike was pretty much un-abused though neglected, sitting in a storage bin from '93 to '04. I've put ~2000 miles on it since purchase, and it still only has just over 10K miles on it.

On my regular hour-long commute this morning, I stopped at Dunkin Donuts at about the halfway point. When I left from there, at the next light, I noticed the engine no longer makes the sound. It still runs great, but I mean it's just suddenly quiet. It's not like it faded over time, it just stopped.

So at the next light, I hurried through the gears with heavier acceleration at low rpm to see if the noise was still eveident. Nope. Quiet. Running great. In fact, it seems to have more power.

What the heck?
:huh:

Post edited by: Biquetoast, at: 2006/11/17 10:47

When was your last tune up ? Ignition timing ?

did you happen to put ear plugs in? my bikes run 100 times better as soon as i plug my ears.

arai59 wrote:

When was your last tune up ? Ignition timing ?

I did that all early this year. Everything is gone over (carbs, new coil, ignition, etc) except valves.

flht1997 wrote:

did you happen to put ear plugs in? my bikes run 100 times better as soon as i plug my ears.

Well, it's really not running any different, if maybe a tad better. That could be an illusion on my part, since there is no noise.

No ear plugs. I mean, even if I did, I would still hear the diesel-like noise, just quieter. But the noise is gone.

My hunch is that The valve clearance has suddenly changed, but not in a apparently damaging way. Oh.... I wonder if a bolt snapped inside... like a camshaft bolt.. crap, I have to ride home still....

Biquetoast wrote:

My current commuter 750 has always had a certain engine noise, ever since I got it two years ago. The noise is a bit of a diesel-like sound, not loud and really only there under acceleration at low rpm.

Using 89 or 94 gas lately? Maybe the station you frequent quit dumping ethanol down the filler pipes at 3am.

Sounds like a (minor) detonation issue.

Valve/shim noise is usually loudest right at idle - or a little above.

Hard to guess which "diesel-like" sound you're referring to - they're such noisy critters to begin with... :lol:

Pterosaur wrote:

...Using 89 or 94 gas lately? Maybe the station you frequent quit dumping ethanol down the filler pipes at 3am.

Sounds like a (minor) detonation issue.

Valve/shim noise is usually loudest right at idle - or a little above.

Hard to guess which "diesel-like" sound you're referring to - they're such noisy critters to begin with... :lol:

It is pretty hard to describe the sound. I chose "diesel-like" bacause it's pretty good and I've heard other people mention it. Thought it might ring a bell or two...

Detonation, huh? Hmm. You mean pinging, right? I don't *think* it's that, because it make the sound with every revolution, even at idle, but was *most* prominent at acceleration at low rpm. Remember, lots of low end on these 750, so I'm talking about "getting on it" at 1200-2000 rpm...

Oh, and gas is 87 US Octane. Regular. Always.

Also, it was about 35F degrees at the time it happened. Or stopped happening, as the case may be...

If the noise went away the problem fixed itself(that's the way my dumbass boss thinks). :dry: :S :huh: :whistle:

Quick thought, it may have been your timing advance unit was stuck in one position and it finally broke loose.
Ride safe,
Les

I hope it wasn't a timing chain guide that was loose and is now broken.

It's got to be the "KAWASAKI GODS" smiling down upon you! In other word...you dun bin blesd.

Happy Ridin'

Thanks for all the suggestions, guys. I think what I'll do is just do an oil change and put 'er up for the winter when I get home. Then later I can check the valves - I was going to anyway - and see if something's goofy.

I hope I make it home today...

It just sounds like there was one really noisy valve/cam lobe/shim/etc that suddenly got quiet.... That just can't be normal...