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Fuel Question

  • Thread starter Thread starter dw200
  • Start date Start date
D

dw200

Guest
Question for anyone...How well will these bikes run on high octane, leaded fuel? I have access to all of the 100 Octane, low lead aircraft fuel that I want. It would have to be cut a bit with street gas as it does not have the additives that street gas does. Do you think it would help or hurt or no difference? Oh, my bike is a 82 GS650G. Thanks in advance.
 
The Suzuki GS bikes are made to run on low octane fuels. The only time I've run anything higher than 87 is in extremely hot weather (100 deg f +) in the desert, in towns (stop & go traffic) and high altitudes with hot weather. Then I only go up one grade. It would be a waste of expensive fuel to run 100 octane in your bike.
 
i ran a 63 sportster once on aviation fuel mixed with reg unleaded and i got a stuck valve twice. (im a slow learner).
 
Check out your owners manual, these GS bikes differ from each other.

My 78 gs750 calls for at least 90 octane LEADED or Low-Lead.

While my 82 650 needs 87 octane Unleaded or Low-Lead.

100 LL would probably be too high to use alone.
However LL still contains approx. 2 grams of TEL(lead) per gallon, and I know some people that toss a little LL in with their pump gas with no problems.

Just sayin...
 
Please be aware that "higher octane" does NOT mean "higher power".
noway.gif


It's a measure of knock resistance, not energy content. "Premium" gas actually has fewer BTUs per gallon than "regular" gas.

.
 
Haha just realized the OP's bike is a 82 650....which means you should stick to 87 pump gas, that's what the manual calls for.

But like he said, higher octane doesn't mean more power on your bike.
It will cause you to run hotter and the Lead can foul your plugs out.

You should just give the LL to me instead....
 
Steve said:
I won't argue about the "foul the plugs" bit, but why would it run hotter?

It has fewer BTUs and burns slower, so it would tend to run COOLER.
shrug2.gif


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Click to expand...

Yep that's technically correct in regular gasoline applications.

But, 100LL has much less density(lighter) than regular or racing gasoline, which can cause lean conditions at higher RPM's much easier.

If you look on drag racing forums, many people complain of these hotter runs.
I guess it also depends on the compression ratio and jetting.

But hey, there's always conflicting stories...

When I worked at the airport, a lot of guys ran it in their race cars
and most of them complained about the heat....ehh who knows!

----

EDIT: I was wrong about the "leaded" comment, my bike actually
calls for unleaded or Low Lead.
 
Last edited:
Leaded fuels were done in the early 70s. The more important measure is the "Octane" rating. The GS series were supposed to run on 87 Octane. My GS always rattled (pre-ignition) on 87. Since timing was not adjustable on OEM systems, I just moved up in rating. 91 was fine, 93 was overkill, 89 was hit and miss, 87 was a certified rattle. What you need to do is to find where that point exists for your bike. Any higher octane is wasted, any lower is dangerous.
 
TRhat's a very good question. i would love to know the answer. my dad says in a bike fuel is fuel. Doesn't matter how high the octane. In my '62 cadi i only put 91 b'cuz it made a difference, but i'm not positive what effect it has on a bike.
 
Comparatively speaking, most every stock GS runs a pretty low CR. I've never had a GS knock on 87, 87 w/ethanol or anything. If you've dropped a high CR borekit, go with what the manufacturer calls for. Otherwise 87 is fine. Even my ZRX with a higher CR than a GS calls for 87 in the manual.
I don't recall ever seeing in any of my 750 manuals it stating to run 90.
Then again, I never looked either.
 
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