High Octane vs. Low Octane noises!! What's up?

[BigDaddyD]

So this may just be gasoline 101 type stuff, but regardless... I don't know.

I was running on the cheap today, so I put some regular unleaded gas into my '77gs750 and noticed that the engine ran significantly quieter once the gas made its way into the system.
There was hardly any valve clatter at idle or while revving which I had noticed while using Premium, and originally figured it was due to valve adjustment issues.

So my questions are....
Is the Lower Octane better for my bike or are the valves in need of servicing?
And why would the Higher Octane cause valve clatter anyway??
Did or could the higher octane do any damage to my engine?

(I say clatter because there's no distinguishable knocking, tapping, or pinging, it's more of a "lose change in a metal dish" kind of sound...)

Thanks all!
And...
Yippie! The Forum is back!
Thanks to the web-guru's for not giving up on us!!

[Steve]

Rather than re-type all that info again, here is a quote from a previous post I made in response to a similar question:

Stock bikes (even ones with pods and pipes) run best (in most cases) on 87 octane, REGULAR gas.

There is no extra power in higher octane, in fact, higher octane fuels have fewer BTUs per gallon. Advancing the spark does not give you more power, either. Both of these 'tuning' items, high-octane fuel and spark advance, are band-aids to make up for the problems introduced by high compression, which is what really makes the power.

Higher compression generates more heat which might light off the fuel mixture before the spark. Higher-octane fuel will resist that because it's harder to light and waits for the spark. It also burns slower, which is why you have to advance the spark to start the fire earlier.

If you run higher-octane fuel (notice that I try not to call it 'premium' fuel?), it will not be completely burned before the proper time, which will probably lead to deposits on your valves and pistons. These deposits will cause problems because they can glow red-hot, lighting the mixture before the spark.

Until you get into changing the pistons and cams, REGULAR gas is just fine.

In other words, if it runs better on "regular", use it. After all, it's what is recommended by the manufacturer.

.

[Nessism]

My guess is that the issue you describe has nothing to do the the type of fuel. Does your bike have a fuel gauge? Maybe the float in the tank was making the "loose change" noise, and now that you filled up, the noise is gone.

[82Shafty]

So this may just be gasoline 101 type stuff, but regardless... I don't know.

I was running on the cheap today, so I put some regular unleaded gas into my '77gs750 and noticed that the engine ran significantly quieter once the gas made its way into the system.
There was hardly any valve clatter at idle or while revving which I had noticed while using Premium, and originally figured it was due to valve adjustment issues.

So my questions are....
Is the Lower Octane better for my bike or are the valves in need of servicing?
And why would the Higher Octane cause valve clatter anyway??
Did or could the higher octane do any damage to my engine?

(I say clatter because there's no distinguishable knocking, tapping, or pinging, it's more of a "lose change in a metal dish" kind of sound...)

Thanks all!
And...
Yippie! The Forum is back!
Thanks to the web-guru's for not giving up on us!!

I have the Suzuki owners manual from my Dad's bike that I need to get over to cliff, but in there it says anything from 87-95 octane can be used in our bikes.

I too noticed that my bike runs quieter on 87 octane. What I also noticed though, is if I take off a bit hard from idle, when it she is hot, she will ping for about a second.


8.8:1 ratio on an aluminum head should never require premium, but if it is an only option, you can use it.

[BigDaddyD]

My guess is that the issue you describe has nothing to do the the type of fuel. Does your bike have a fuel gauge? Maybe the float in the tank was making the "loose change" noise, and now that you filled up, the noise is gone.

No there's no fuel gauge. It's definitely noise coming from the engine. I would always hear it, full tank or empty. She just made a lot of clatter, but once I put in regular unleaded gas and not premium the clatter stopped.

I just wanted to be sure I didn't hurt anything (burning up the valves or something) by running premium.
But if all the manuals say 87-95 octane is fine then I guess she just prefers the cheap stuff.
And I didn't notice any performance difference so...
I'm sure not gonna complain about a cheap date! ;-)
Just wanted to make sure i didn't hurt anything.