Rattle at low fuel normal?

[The Wisco Kid]

When I'm down to a quarter tank or so (1gal) I hear a pronounced rattle echoing up through the tank. It's timed with the engines rpms so I don't know if this is just hearing the engine through the tank, or if it's a problem. It's only audible from about 1k to 3k rpms. I don't really like the sound of it, but if it's normal I can deal with it.

It's a 1981 GS450E with about 8k mi on it. Just had the carbs pulled, cleaned, and synched, but it made this noise last season too. I haven't been riding that long and this may be a dumb question, but if you have any ideas? Could there be something loose in there?

[bwringer]

When the tank is nearly empty, it can act as a resonator and amplify normal engine noise. Or maybe the mass of fuel in a full tank damps out noise better.

Either way, it's normal and harmless.

[ddaum]

If you have a fuel gage, could it be the float rattling around in the tank??
That's just an idea....

[The Wisco Kid]

no fuel gauge. but sounds like it might just be normal. just was making sure. thanks!

[Chris Daniel]

My gs650 did this when it would get below a half tank. It would start making a knocking sound that only got worse as the tank got emptier. I finally found out it was the vacuum diaphram in the stock petcock making the noise. The tank was acting like a resonator and making it extremely loud the emptier it got. I switched to a pingle manual petcock and the noise went away completely.

Hope this helps.

[JMHJ]

I also noticed noise in my old GS450L when the gas was low. I wondered if it might not be valve train noise? I put 18 or 19k on it without any adjustments of that kind, and I don't remember the noise when I first started riding it. In any case, filling it up made the noise all but go away, and made me feel better.

[gazwpowell]

GS450E Ratthle

It may be worth reading the replies to my post on 14th May.

Search for GS450E

Sounds like rattle on tick over is a common issue.

I thought it may be to do with mixture but I am still evaluating the results of my amateur carb tuning.

Gary