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Discussion Starter · #1 ·
Just wondering if anyone can tell me what type of fuel i should be running in my 85 gpz 600.

I belive it was mid to late eighties when leaded fuel was taken of the market here in australia we now have unleaded with a 95% octane rating and premium wich is 98% octane(or so they say). the differance is the leaded fuel actually lubricated the valve in some way. you can now buy an additive to put in the fuel if your car/ bike was ment to run un leaded that does the same job.

you guys probably call your fuel different things over there but im sure i will figure it out.

leaded fuel or super as it was knowen was 98% octane as well.
 

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The Cruising Gunsmith
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The general consensus I have heard is that a 1985 bike should be able to run unleaded no problem. The octane requirement is probably in the owner's manual. If I recall, back in the late 70's "regular" was 91 octane and "premium" was about 95. To make it more confusing, they used a different octane number back then. Today, regular is 87 octane and probably equivalent to 85 by old standards. So, if an old bike was designed to run on regular back then, it may need premium now. Best to just try regular and see if it runs OK. If it does, that's all you need.

My 1979 KZ750 has never run right on regular gas.

As for the "lead substiture" products to lube the valves: I have used them for years. It's very cheap insurance. here in the US, I recently found an actual tetraethyl lead octane booster product which I started using since my bike was made to run on leaded fuel. Some say it's not necessary, but that's what it was designed for.
 

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Discussion Starter · #3 ·
The general consensus I have heard is that a 1985 bike should be able to run unleaded no problem. The octane requirement is probably in the owner's manual. If I recall, back in the late 70's "regular" was 91 octane and "premium" was about 95. To make it more confusing, they used a different octane number back then. Today, regular is 87 octane and probably equivalent to 85 by old standards. So, if an old bike was designed to run on regular back then, it may need premium now. Best to just try regular and see if it runs OK. If it does, that's all you need.

My 1979 KZ750 has never run right on regular gas.

As for the "lead substiture" products to lube the valves: I have used them for years. It's very cheap insurance. here in the US, I recently found an actual tetraethyl lead octane booster product which I started using since my bike was made to run on leaded fuel. Some say it's not necessary, but that's what it was designed for.
ive been running premium in the bike it dosnt seem to run right on reguler either, but thats good news(85 should be ok with leaded) thanks
 

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What do you mean buy not running right?

Unless you're running a modern super sport there's no reason you need to run premium. Even the 2008 GSX-R 600 only recommends regular.

Generally, the only time you need premium is when you have a ridiculously high compression ratio or you hear pinging.

However, by 1985, are you sure your bike was designed for leaded fuel? I don't actually know but I'd think the Australian 600 was just a Japanese or American spec engine (or very similar). That's to say, it was probably designed to run on unleaded fuel even though lead was still used in Australia until later than other countries.
 

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The Cruising Gunsmith
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What do you mean buy not running right?
On my 1979 750Twin, it would sometimes misfire and stumble in the "lean zone" between about 2k and 3k RPM at light throttle openings.... and it always seemd to be right at the RPM I was trying to cruise at. I could also hear "ticks" sometimes like predetonation.

It may be because my bike has always run lean in the "pilot jet" area even when stock. It's a Californai model so it is probably smogged out... it might not bark at lower octane with a richer mix.
 

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Discussion Starter · #7 ·
What do you mean buy not running right?

Unless you're running a modern super sport there's no reason you need to run premium. Even the 2008 GSX-R 600 only recommends regular.

Generally, the only time you need premium is when you have a ridiculously high compression ratio or you hear pinging.

However, by 1985, are you sure your bike was designed for leaded fuel? I don't actually know but I'd think the Australian 600 was just a Japanese or American spec engine (or very similar). That's to say, it was probably designed to run on unleaded fuel even though lead was still used in Australia until later than other countries.
running regular fuel there seems to be a slight knock at low revs and it also seems to lag a bit in the higher rev range

running premium, runs nice.

but your right the 85 gpz 600 does run the American motor it is also stamped zx 600a on the frame and complance plate.
 

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You might try getting colder plugs as well, or try turning out your pilot screws to make the mixture at lower RPMs a little richer, reducing pinging/knocking.

If I recall Japan passed laws to limit lead in gas years before most other countries. I can't seem to find any websites to back this up though so I'm probably wrong.
 
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