My engine produces fairly audible rattling noise under acceleration in 3000-5500rpm range, no matter the speed or gear. It's been there since I bought the bike. I thought it's valves, but I recently had them done.

The noise is there only when I accelerate, no matter slow or fast speed I am at. It sounds like fast constant  grinding or rattling sound, maybe gr-r-r-r-r-r-r and goes away when the load on the engine decreases.  It rattles till I get to fairly constant speed. It stops when the engine does not have to pull hard and just maintains the speed. I basically can cruise with no rattle but as soon as I roll the trottle and the engine pulls there's the noise.

Nothing at idle. I am pretty sure it's the engine, but.. Could that be the chain? The tension is within specs (though I never replaced the chain/sprockets, they look great at 8k miles). Could that be the wheel alignment (never checked that)?

I adjusted valves. I checked the cam tensioner. I checked chain/sprockets. Changed the oil yesterday and always check the level religiously. I even put V-Power Shell premium gas in today (otherwise I always run on Regular). Still there.

Interestingly enough recently I did the DIY ignition advancer and the noise is actually more audible. Could it be because the bike pulls stronger (and it subjectively does with the advancer set to 17 degrees). I rolled back the ignition plate and the clicks are still there, just a bit less loud (really subjective measurement, maybe I traveled noisier roads after the roll back, so don't hold me countable for this, merely an observation).

I'm not sure if that's detonation pings. With Premium gas they should not occur at all in our engines, right?. I read about camshaft free play noise (at idle) and some other noises "native" to our engines but could not find pertaining information for my case.. Cam chain?

There's simply not much else left to check. Should I just live with it?

Something similar was described in this topic http://gstwins.com/gsboard/index.php?topic=19575.0 and appeared to be the chain. I have a new chain on the shelf. Maybe I try that?

I am puzzled. Help!

TIA

Check to make sure the centre stand isn't hitting the chain, I've lost the rubber stopper that attaches to my muffler that makes sure the centre stand is low enough it won't hit the chain, so my chain hits the centre stand the moment it comes a bit loose, and has the same sort of description of yours (only under acceleration/deceleration, same sort of noise)

A pretty obvious sign of the chain hitting the centre stand is that it'll eventually grind a groove in the stand...

Just went and checked. Nope. The rubber rest is in place. Good point though! I appreciate your help.

Keep 'em coming guys! Thanks.

When I brought mine in the get it checked out and asked about pretty much the same thing the mechanic said that there is just a little play in the cam and that it doesn't cause any real problems other than an annoying noise

Can't believe it's been over two years now since I first posted the original topic! Anyway, here's my update on the rattling engine sound. It took about two years and about 2k miles but the rattle is still there and now a bit more pronounced (louder).  It is still constant not speeding up when the engine revvs up nor slowing down when  the RPMs lower.

I just did the valves (three valves were out of specs by just +0.02, I fixed it) but the rattle didn't soften, it is still there. I guess it is "normal" for my bike after all.

I did the new chain and front sproket last year, with no effect on the rattle. The chain tension has been just checked again. The sound seems to come from the engine, from under the gas tank (camchain?), not from under my feet (transmission gears? chain?). It's hard to pinpoint.

Important thing I almost forgot to mention. Lately the gears seem to be a little harder to switch, more often stuck in neutral.


I just don't want it to sound like a bucket of bolts in a year or two!!  

TIA

I think I have the same thing seems to be getting louder the more miles, hope it is not the transmission, seems to go away when decelerate or pull in the clutch.

reminor,
Are you just letting this problem go? My 1992 GS500 has this exact same thing. It's got 41,000 miles, so I was considering partially rebuilding the engine to fix it.
Can I fix a 'little play in the cam'

I think you guys are describing spark knock. Knock occurs when there is sufficient pressure in the cylinder (ie. under load) to ignite the air/fuel mixture before the spark plug sparks causing a knocking or pinging sound. the sound is actually a high pressure wave slamming in to a piston (BAD) which if done hard enough long enough will break a piston or gasket or ring or valve or... anyway the fact that advancing the timing made it worse reinforces my point, try running mid or high octane gas. if that solves it bam you've got spark or compression or heat knock. if not then it may be knock from running lean.

Hard to tell without hearing it but it does sound like gas knock to me which I had on my 1st five bikes, 4 Hondas and my 97 GS .  I ran 20W-50 oil summers in the Hondas and 15W-50 synthetic in the 97 GS and they started knocking the second season and got progressively worse as the miles built up on the bikes and the carbon built up in the cylinders.  The problem was eliminated or greatly reduced in all cases by switching to premium gas summers.

After about 50k miles on the 97 GS I switched to the less expensive 15W-40 heavy duty oils (Delvac, Rotella T, Delo) due to increased oil consumption and the 97 GS never knocked again on regular gas year around.  I changed to the same heavy duty oils on my 02 GS which I bought with 4k miles on the clock the first oil change and its gone 73k miles on regular gas year around without ever having gas knock.

Try premium gas for a tank or two first to see what effect it has on your knock if your using regular now and then change to a XXW-40 oil next change if your using a XXW-50 oil now to see if that helps eliminate the knock.  A air cooled mc engine will run cooler on a 15-40 or 10-40 than it does on a 20-50 or 15-50 oil.  The oil carries the heat from the combustion chamber to the sump and oil flow is reduced with a heavier oil.

they're not talking about detonation. i know the sound you guys are talking about, i got my bike with 256 miles on it and it made the sound it still does today. i always thought it was a valve issue, but it's never caused any problems or lack of performance. and i've also heard about the noise coming from the cam, so who knows.

I have same noise, think it's coming from clutch and it's harmless. One feature that Suzuki just have.

Im not sure if I can make it clear just how freaking loud this noise is. It's louder than my full Vance and Hines system (which I'd consider pretty loud) and you can apparently hear it when riding next to me over three other bikes.

I think it's getting worse. I rode it today and now it does it at 1,500 rpm as well. It does it all the way up to about 6k while accelerating, but not when I let off the throttle. It didn't use to do it while sitting, but now it does.

Is this still the same issue or not?

Thanks guys!
-Amanda

well, no lol. it's not near that loud, you've got somethin goin on there

(posted in wrong thread ... sorry)