Premium Fuel?

I have always run premium fuel in my 1975 KZ900, not sure why, I think my bother-law, previous owner said that's what he always ran.
So the compression ratio is stock at 8.5 to 1. Shouldn't it just be regluar fuel?
Pro, cons either way?
Thanks.

I have always ran premium in mine I have noticed if I don't there is a slight valvetrain rattle at certain throttle positions. I usually run it in my lawn equipment to. I have heard that once a motor gets used to premium it wont run worth a damn on regular any more. Who knows maybe its true

Science might say I am wrong but i have ran premium in my bikes for a long time and never had a fuel related issue.

Try running a tank or two of each and see if you can tell the difference. I would be interested in members thoughts also


What happened to the Amoco White gasoline. Do they still manufacture it or is it part of the BP stable now? That was good gas back in the day

Unless it pings on regular, no reason to run premium.

bountyhunter wrote:

Unless it pings on regular, no reason to run premium.

+1
I have always run nothing but regular gas in all of my stock KZs with the exception of my KZ1300 which requires premium or at minimum mid grade since the 9.3:1 compression. On very hot days you might be able to see better results with higher octane gas. The easiest way to tell if the bike will run better on higher octane gas is to go to the hardware store and buy a quart of Xylene (Xylol) Take it with you on a little trip with a full tank of gas. see how the bike runs on that tank of regular for about a half hour or so. Than dump the quart of Xylene in the tank and see how the bike runs with the Xylene. Xylene has an octane rating of 117 and will change your fuel octane enough to affect the performance if the engine indeed requires the higher octane. Xylene is used in most European countries to boost octane the same way we use Ethanol here in the US. Xylene has the benefit of not reducing your fuel energy density which Ethanol will do. when adding Ethanol to raise Octane the engine will go lean. While adding Xylene it will not. This is just a quick way to test if your engine requires higher octane. For My Built GPz1150 I buy Xylene in 5 gallon buckets and mix it with my premium gas. For reference, Ethanol has an Octane rating of 101 and MTBE which used to be used here in the US before Ethanol had a rating of 118.

yesterday I accidentally put premium into my bike and I have to say it ran really well, better than with regular I think. It was a warm day, around 27 celcius, so that likely had something to do with it...

There is a factor to be considered. If the engine is in original condition and the head has not been removed, there will be a lot of carbon built up on the piston crowns and inside the combustion chambers. This will raise the compression of the engine considerably over the stock 8.5:1. In such cases the premium fuel will make the engine run better. The problem now is that not all of the cylinders are running with the same compression. The question now is; Do you want to take advantage of the "dirty" situation for the extra power, or do you use combustion chamber cleaner to restore the engines original condition? I am of the sort that prefers to have clean combustion chambers and rings that do not stick. I use "Mopar Combustion Chamber Cleaner" on a regular basis. This product can be bought at any Chrysler/Dodge dealer. We did a couple of threads about this subject. Do a search for that key phrase. In another post I showed what the inside of the engine looked like after I used this product. I was totality surprised and it made me a convert for its use.

Just another thought - the reason I usually run Regular (even with my 10:1 pistons) has to do with shelf life. Regular fuel gets turned over faster at the pump than mid or high octane fuel does. This means your odds for bad or stale fuel tend to be lower.

Here in the Chicago area that would not be the case. Since today MANY car engines require Premium fuel, the time that the fuel sits in the ground is insignificant. What is significant is that not all companies use the same additives. If for example you let American fuels sit in the tank and inside carburetors too long, it will turn to a brown tar and is nasty. If you take most Australian and European fuels, you can leave them sit in the vehicle indefinitely and all that will happen is that it will dry out. If for example you take an aircraft engine which runs on "Av Gas" apart, you will find that it is completely clean inside the combustion chamber unlike a "road" engine which runs on "Mo Gas". It is the additives used here in the US that make your gas go bad. Some are much worse than others. There are some "Octane increasing" additives that are actually made from "coal tar" and "heavy distillates". It is these additives that muck up the inside of your engine. If you are worried about stale gas than buy it somewhere near an express way. You will not find stale gas being a problem.

otakar you seem to be pretty knowledgeable on the subject. Do you remember the Amoco White gas what happened to it?

I know someone who swore that mothballs would increase octane if you crushed them up and put into the gas any truth to this?

otakar wrote:

Here in the Chicago area that would not be the case. Since today MANY car engines require Premium fuel

Up here, eveyone is cheap. Even others that I know with cars that require 91 octane still pump 87/89 to save a few cents.

You guys still can get Regular (leaded) gasoline or are you using the terminology loosely depicting lower octanes unleaded....

BTW... Otto, hope your garage never catches fire.... Holy crap with all the chemicals you had on your shelf....

Just my 2 cents, but I have found something equally interesting. 'Round here all the Gas has 10% Ethanol added ....EXCEPT one station that sells 100% Gas, My cars, truck and bike ALL run better on the 100% gas.
Yeah it costs .03 a gallon more .
Runs MUCH better on plain regular 100% gas!
ED