What should I fill my bike with?

[Rich82GS750TZ]

So the short answer is ....... Gas. Fill it with gas. And ride it.

[limeex2]

I put in high compression pistons in a Triumph Sprint 900. Never checked to see what gas i should use with the new pistons. Dyno tuning confirmed a lean spot at 5000+/- rpms. That is right were the bike ran 75% of the time. Heaven forbid my cheap ass would spend .07 cents on a gallon gas, nope. 24k later, porcelain part of spark plug broke off and dropped into the cylinder. Took out 3 of 4 valves. Fixed, but did not fix the cause, (lean detination)which I knew, but was to stubborn to address it. 20k later it happened again. Engine basically toast. Same issue. Moral of the story: 1) I'm a stubborn old German. 2) Any mods to motor/carbs/exhaust will change fuel requirements from stock, so paying more for gas is like paying for health insurance. Ya hate paying for it while your healthy but glad you have it when you get sick. 3) Run what ever your comfy with, but I have to much $$ tied up in carbs and dyno work to save $2 a tank. I've simplified it. On my everyday drivers I use 87. Everything else I use 91 non-oxy, Lawn mowers, snow blowers, weed whips, chain saws ect. That same Triumph would barely start after sitting 3 weeks. Had to drain carbs. In my truck which gets run maybe 1x per mo, I have started using Star-Tron(cuz its cheaper! lol)) as I had severe water/fuel issues with truck from letting it sit with 87 octane.

[greg78gs750]

Steve and bwinger are right on, 87 regular standard ethanol blend here and never any problems in....15ish years of gs ownership.

[wyly]

Steve and bwinger are right on, 87 regular standard ethanol blend here and never any problems in....15ish years of gs ownership.

I just go with whatever premium is in the pump, never had an issue. I ran into a guy with a CBX like I have and he only uses race fuel, an expensive waste of money imo, My cbx and gs run just fine on premium and even regular if need be.

[timebombprod]

whatevers fine id say, saw a report that said 89 was the best for the bike for performance but im sure 87 doesnt make it run like ####. if your bike doesnt always get ridden and may sit around for a bit, non ethanol doesnt degrade as fast as ethanol and wont cause corrosion or rust (as easy, not entirely sure)

[poway23]

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

[80GS1000]

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.

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

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.

.

[80GS1000]

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

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

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.


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.

[Longitudinal]

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.