What should I fill my bike with?

[Guest]

I bought my 1981 GS1000g new. Here with California gas, it never liked 87 octane and would knock when it was hot and the engine was under load. Fearing engine damage from all the knocking, I switched to 91 octane. 39 yrs later and she still doesn't knock..

 

[GalDemSuga]

Guys

I wanted to add the piece of value just incase anyone else needs it. It is a list of ethanol free stations around the US and Canada and it allows for updates to be made to the list.

https://www.pure-gas.org/index.jsp

 

[Guest]

GalDemSuga- good info there. Thanks.

I run 91 octane booze free petrol in my GS but only because it has high compression 10.25:1 pistons to prevent pinging/detonation. If the motor was close to stock I'd run just regular unleaded.

 

[Steve]

I run 91 octane booze free petrol in my GS but only because it has high compression 10.25:1 pistons to prevent pinging/detonation.

Compression ratio alone is not the reason to run higher-octane fuel. :-k

My wife's new ride has 12.0:1 compression ratio and runs just fine on 87 octane with up to 10% ethanol. :encouragement:

I have tried running 93 octane when available for several hundred miles, keeping a log book, of course, and found absolutely NO difference in performance or gas mileage, so we are sticking with the affordable 87 octane.

Yeah, it's a water-cooled three cylinder engine, but it's still 12.0:1 compression. :-\\\

.

 

[Guest]

Compression ratio alone is not the reason to run higher-octane fuel. :-k

My wife's new ride has 12.0:1 compression ratio and runs just fine on 87 octane with up to 10% ethanol. :encouragement:

I have tried running 93 octane when available for several hundred miles, keeping a log book, of course, and found absolutely NO difference in performance or gas mileage, so we are sticking with the affordable 87 octane.

Yeah, it's a water-cooled three cylinder engine, but it's still 12.0:1 compression. :-\\\

.

Your wife's bike probably has an ECU along with modern electronics like knock sensors, EFI etc which takes temperature/air pressure/RPM/engine load and many other variables into account in terms of dynamically controlling the spark timing and fueling. These modern electronics help prevent pinging and deliver the correct amount of fuel at all times. Also as you mentioned, a water cooled engine has better control of heating, especially in the cylinder head, further preventing knocking. There's a reason air-cooled bikes have such thick cylinder heads - they act as a heatsink to prevent detonation!

Glad the 87 octane works out for you all on that triple.

In an old-school high compression air-cooled engine like my bored out GS1000 without an ECU or any other of the electronics mentioned above, I feel that running high octane fuel is cheap insurance against ping/knock and associated engine damage especially during the hot summer season. And especially because it has a one-size-fits-all static spark curve (CDI ignition) and static fueling (carbs).

YMMV.

 

[Rich82GS750TZ]

On a bit of a tangent:

Has anyone heard from the OP, ZombiePotatoSalad. His last post was a video of his bike finally running and him riding it on 6/25/20. I sent him a PM out of concern on 8/6, but got no response. He’s a very inexperienced rider, just starting to get his brasketcase of a bike on the road. He’d been a regular poster up until that video. Many of us had been trying to help him along with advice and encouragement. Hate to think about anything that May have happened, but my mind goes to dark places sometimes.

 

[Steve]

Your wife's bike probably has an ECU along with modern electronics like knock sensors, EFI etc which takes temperature/air pressure/RPM/engine load and many other variables into account in terms of dynamically controlling the spark timing and fueling. These modern electronics help prevent pinging and deliver the correct amount of fuel at all times.

You would be correct on all counts. :encouragement:


I was not trying to say that your bike would run fine on 87, just saying that higher compression was not the only reason to use higher-octane fuel. There are definitely many reasons to use higher octane. If I remember correctly some of the carbureted Harleys had a relatively low (less than 8:1?) compression ratios, but still required high-octane fuel, due to the heat in the engine and the large diameter cylinder bore.

.

 

[GalDemSuga]

On a bit of a tangent:

Has anyone heard from the OP, ZombiePotatoSalad. His last post was a video of his bike finally running and him riding it on 6/25/20. I sent him a PM out of concern on 8/6, but got no response. He?s a very inexperienced rider, just starting to get his brasketcase of a bike on the road. He?d been a regular poster up until that video. Many of us had been trying to help him along with advice and encouragement. Hate to think about anything that May have happened, but my mind goes to dark places sometimes.

Yeah, we need to find out if OP is good and safe.

 

[Guest]

Your wife's bike probably has an ECU along with modern electronics like knock sensors, EFI etc which takes temperature/air pressure/RPM/engine load and many other variables into account in terms of dynamically controlling the spark timing and fueling.

And just as importantly, a modern combustion chamber and porting that benefits from the last 40 years of learning about what works and what doesn't. Our 8V engines are fine for what they are, but they are crude by modern standards. That's not to say that I want modern. I accept crude as a compromise to get the aesthetics that I want.

 

[wymple]

My 82 GS1100 liked it's octane at 91 or better in hot weather. Ethanol is less likely to ping & I could run the grade lower 89 with the same results. My 81 GS850 seems to not care what's in it. My bikes are currently 1977, 1981, & 1984, and a 2010 maxi scooter. I have never had one iota of trouble with ethanol in any of them, and here in Iowa it's cheaper by a bunch. The only fuel injected one in the bunch is the scooter.

 

[Carter Turk]

I haven't worried about ethanol free in my wife's stock 1150 engine, but I did try to use ethanol free in the Kat when I had a big bore kit installed before blowing it up in 2018. I did have 15 + years trouble free with big bore installed, even a 5500 mile ride round trip to Michigan, but problems arose from the starter clutch exploding multiple times.

I can say that I experienced 10 mpg less with 10% ethanol on 400 mile round trip.

The beater 2004 750 track bike I acquired, apparently was mapped for 50/50 92 octane/110 race fuel @ $70 per 5 gallons or pure race fuel.
I honored the mapping for 2 years riding the bike @ only trackdays & in those instances a performance gain is definitely felt thru the leathers.
Don't think it's really worth the expense monetarily, especially on the street, but it sure is apparent when twisting the throttle.

 

[Guest]

There is a lot of discussion about gas with ethanol. In my area, there is no option, it all has up to 10% ethanol. I have never noticed any problems. I treat it before storing for the winter, but that is the only time I do anything special.

There are a couple; the closest would be in Kettering: marathon gas @ 1890 E Stroop Rd sells 91 octane ethanol free, but it is very expensive. I only use it if I don't plan on riding any time soon. Casey's general stores sell ethanol free as well, but they would be a bit further away for you.

Otherwise, manual for my GS calls for 89 octane.

 

[wymple]

Around here, all Casey's have is 87 octane, one ethanol, one ethanol free. Ethanol is supposed to be worth 2 points of octane rating, and my experience says yes.