Premium gas or regular?

yea dogs usually dont get to upset about car rides lol

Hatchet wrote: What's the scoop here? Could this be causing me problems?

The bike is a 1983 KZ750 twin.

Not likely. IIRC, back in the early 80's regular gas was 91 octane which is like premium today.

My 750 twin never ran right on 87. I run 89 now but also add lead octane booster which kicks it up to about 91.

You guys do realize these bikes were designed to run on pond water in stock form right? :laugh:

Octane is just a stability rating. So running on the lowest you can without knocking is right, that's the whole point of it. It's unlikely that putting premium would cause it not to run right though. Premiums a little harder to ignite, which is why you use it with turbos and high compressions, prevents pre-ignition, i.e. knocking. But if your spark is good, it should be plenty easy to ignite at the correct time. You'd have to have an insanely borderline ignition to run fne on regular and not on premium, doesn't seem likely to me. Anything running right should be perfectly able to run on higher grade pump gas than it really needs.

The owner's manual for my 81 KZ650 says to use 87 octane or higher [(RON + MON)/2].
I've tried all 3 available grades & never noticed a difference, so I just use regular.

Del_Herring wrote: Octane is just a stability rating. So running on the lowest you can without knocking is right, that's the whole point of it. It's unlikely that putting premium would cause it not to run right though. Premiums a little harder to ignite, which is why you use it with turbos and high compressions, prevents pre-ignition, i.e. knocking. But if your spark is good, it should be plenty easy to ignite at the correct time. You'd have to have an insanely borderline ignition to run fne on regular and not on premium, doesn't seem likely to me. Anything running right should be perfectly able to run on higher grade pump gas than it really needs.

X2

87 oct. in the Ford Ranger with over 200,000 miles and no problems, with the engine that is .

I have been using them all in the bike this year and found that the hotter the day the higher the octane is my new motto.

Right now I have 87 with some Marine Sta-Bil in it.

JD

lushbaugh wrote: yea dogs usually dont get to upset about car rides lol

mine does if he doesnt ride shotgun

I was told years ago by old gear heads, the octane rating should match your compression ratio.

Example
8:1 = 80 octane, 9:1 = 90 octane, and so on.
And NEVER use any gas with corn in it. (Ethanol)
The alcohol isn't good for motors.

My uncle went to a Briggs and Stratton engine school for small gas engine's and came back preaching this to his customers.
It got to the point, that if you used ethanol in your engine.
He would refuse to work on it.

"I have been using them all in the bike this year and found that the hotter the day the higher the octane is my new motto."

Hadn't thought about the effect of the outside. That may be an issue with air cooled motors in warmer climates. Especially if you're running on the lean end of things (running rich cools the cylinders). If the engine's hotter, you'll be closer to the limit of detonation. I'm in Ohio now, so it's never hot, and I haven't had problems with knocking in the engine just running the cheap stuff. Maybe if I was still in Phoenix. I think for longevity, the real concern is whether or not you're getting your gas from a decent station. I've found some interesting things in gas from low-end stations before. And lost a fuel pump to some bad gas in my truck once.

You can get into all kinds of crazy stuff to mess with what octanes you need. But as long as you aren't getting any knock, you're fine.

For reference, my Mazda, which peaks at about 18psi of boost, with a 9.5:1 compression, can run on mid-grade, but will slightly retard the timing. Only noticeable if you're at full throttle, and even then barely. Something tells me our beloved KZ's aren't quite so sporty in the engine tuning department (though they're still quicker in a line, something about not weighing 1.5 tons).

K.D. HART wrote: I was told years ago by old gear heads, the octane rating should match your compression ratio.

Example
8:1 = 80 octane, 9:1 = 90 octane, and so on.
And NEVER use any gas with corn in it. (Ethanol)
The alcohol isn't good for motors.

My uncle went to a Briggs and Stratton engine school for small gas engine's and came back preaching this to his customers.
It got to the point, that if you used ethanol in your engine.
He would refuse to work on it.

Yeah I remember when I was a kid everybody I knew that was a gearhead thought chevys and Harleys were the only way to go,of course none of them had ever ridden a big bore kaw though! :woohoo:
Ive run 89 since the early-mid 80s without a problem,maybe its because I don't leave gas sitting around bad enough to go bad(My service van averages 30,000 plus miles a year! :woohoo: )

I agree that the ethanol is of no performance value, nor mileage value. I undrstand that it only has about 2/3 the power output of petroleum fuel. So if there is 10% ethanol in your fuel, and that 10 % is only 2/3 as powerful, then the ethanol will deliver about 96.7% of the power that full petroleum based fuel will do. Also, in humid weather, an open pan of the stuff will become cloudy within minutes, indicating that it soaks up water like a sponge (like somebody said).

But how can you fine any NON-ETHANOL fuel any more?

My '82 KZ650 runs the same regardless of the octane rating. I think that regular grade ignites a little faster that premium, similar to advancing your timing. So that helps, provided your compression ratio and timing are not too high or advanced. The debate goes on.......