what octane?

I never figured it out. So ill ask you good folk. What octane gas should i be running in my 82 kz750 4cyl?

cherokeekid58 wrote: I never figured it out. So ill ask you good folk. What octane gas should i be running in my 82 kz750 4cyl?

Regular grade gasoline, provided that using it doesn't cause the motor to "ping" under load.
But in any event, if a motor is pinging, would assure ignition timing is correct, regardless of the grade of gasoline being used.

Good Fortune!

Yea, I hear a lot of people say they should have premium. But I see no reason why, it's just a rating of how stable against combustion the fuel is. These engines aren't particularly high compression ratio or anything, so I see no reason to use the more expensive gas.
Like patton says, if you get any pinging, go up an octane rating, but it may be indicative that something else is a little out of whack, timing, or maybe excessive carbon buildup somewhere (the carbon holds heat and can cause pre-ignition).

Oh ive been running mid grade. Which is like 87 something octane. No ping under load. Do have something like a ping at idle, but i think i have an exhaust leak at the one clamp. So its probably just valve noise.

Interestingly, Octane numbers for regular/mid/premium vary by location. 87's regular out here. When I lived in AZ regular was 85, and my poor turbocharged car couldn't ever get the 93 it was supposed to have. Supposedly this is supposed to have to do with altitude (at higher altitude you have less air, hence less fuel burns, hence slightly reduced temp), but I lived in Phoenix, which is by no means up in the mountains. So who knows, I definitely always just go by the pinging. I haven't had problems in my 750 spectre with 87 octane, so that's what I use. The Mazda I drive loses power from retarding timing on 91, and on 89 you can get some wicked pinging if the turbo spools.

Yeah the appalation mountains are literally in my back yard. At some places i think you can even get higher than 93.

I've ridden over 25k miles in the last 2 years on my internally stock KZ900A4 and used all three fuel grades. I consider 2 variables when filling up: elevation and temperature. If I'm riding up in the mountains (above 5000 feet), I'll use 87 because it ignites easier which works better with the lack of oxygen at those elevations. When I'm running around town and it's less than 95 degrees, I'll run mid-grade. When it is 95 degrees or hotter, I'll run premium. If I'm running Seafoam or other fuel system/combustion chamber cleaner, I'll run premium.

I believe the lowest grade was 89 back in the 70's/80's when these bikes were built. I never go below that. Premium not required unless the engine is modified.

Part of the deal is if your a little on the lean side
and it's hot out it may ping from a lean miss fire
then you put in some premium the pingging stopped
then you think you need the better gas
when you realy need to fix the carb.'s

I've always told people, if your bike has stock compression pistons and motor mostly stock, use what the factory manual says to use. If you get ping/detonation increase octane number one step until ping is gone. It will usually be most visible when the motor is good and hot and under a load.

Octane ratings and what they refer to has been misunderstood by most people for YEARS.
Most people think a higher octane fuel is a more flammable quicker burning fuel, but it isn't.
The lower the number of octane the FASTER the fuel burns. The higher the number of octane the SLOWER it burns.
When an engine has high compression, compressed fuel with burn more quickly. And since detonation is a combustion which burns so fast it flashes and only distributes the explosion to one side of the piston and not both sides of the piston equally. This is the knock you hear.

On high compression you need a fuel that will burn more slowly and allow the explosion to distribute its load evenly across the piston resulting in no detonation or ping.
I hope this helps the guys that didnt really understand the full concept.

Oldschoolz, great explanation. I learned about octanes in my automotive class in school. I try to explain the difference in octanes in engines but people just dont get it or tell me i dont know what im talking about. So i stopped trying. Good info here guys. Thanks.

Cheers
Jason