Topic: Gas - What octane do you use?

[Mr Freeze]

I haven't really read any threads about what octane of gasoline everyone generally likes to use in their 750's. I've always used the highest grade that's available at a given station, usually 91 or 93. I'm of the opinion that higher octane gas in these older engine is better for cleanliness of the carbs and plugs overall, but maybe there's some insight to be shed here?

Not really looking for any advice, I guess I'm just curious.....

[Maurice]

No need for anything above the lowest. Unless you're running a turbo or high-compression engine...

Read this.

[flybox1]

the lowest I can get.   mostly 87, and occasionally 85

[edwardmorris]

http://www.motorcycleproject.com/motorcycle/text/octane.html

[Muckinfuss]

based on your initial request of gasoline performance....go here and make up your own mind.

http://www.toptiergas.com/

[PeWe]

As long as no pinging use the lower octane as modern car use.
If pinging, retard ignition or check if carb setup is too lean. If not,  higher octane. I use highest octane available, Shell V-Power when I have higher compression than stock.
There are other fuel additives for cleaning carbs, fuel injection.

[bjbuchanan]

87 here. No reason for higher on anything other than stock. If someone convinced you of the 'benefits' of higher than necessary octane they are flat out wrong. It's a placebo effect at best and builds up excess carbon from unburnt fuel over time

[Bodi]

Shell premium is all I can get without ethanol here, so I use it. I don't know the octane... 91 maybe? You shouldn't need anything higher than "regular" grade unless you a have high compression piston kit installed.

[BobbyR]

For some reason I have been using Premium since the price went down. I don;t think it has made any difference.

[750cafe]

They were designed to run on 89 octane.
If you have either bored it over or added compression ratio, use the best premium that you can find but not over 95.

Eric

[Deltarider]

... and builds up excess carbon from unburnt fuel over time

May I ask where you found that knowledge?

[Wobbly]

98 Octane  in Germany which uses RON standard (thanks to the military, I do not pay German prices). I believe that would be equal to 93 or 94 by U.S. standard. While in Italy, I often use 95 Octane which should equal 90-91 back home.

[my79650]

Run supreme up here which is 91 octane. Regular is 87 but its got that damned ethanol, great if you like cleaning carburetors once a month.

[Wobbly]

I don't seem to have a problem with it, but there is at least 5% Ethanol in the gas here--unless you get the so-called bio gas with 10%.

[70CB750]

I use pure gas as often as I can fill up on it - it comes only as 87.

[DaveBarbier]

Run supreme up here which is 91 octane. Regular is 87 but its got that damned ethanol, great if you like cleaning carburetors once a month.

Anyone else experience this? Not trying to start anything but from taking apart carbs (not too many, just a handful because I'm relatively new to the scene) even after about a year using regular 87 the carbs are really not bad at all. Having to clean carbs once a month due to 87 octane sounds like garbage  talk unless you're actually not riding but letting it sit...but even so, a month? Maaaybe yearly...? At TT mentioned if fresh gas is being run through the system and not being allowed to sit for a long time only the rubber bits are really affected.

You working for the oil companies?!?

...Understand that if the fuel is constantly flowing, being used and being replenished, only the rubber bits suffer.  If the fuel sits in the system for periods of time, that's when other compounds form in the fuel and attack/convert the metal parts.

Cheers,

---
1978 Honda CB550K

[Maurice]

Run supreme up here which is 91 octane. Regular is 87 but its got that damned ethanol, great if you like cleaning carburetors once a month.

Anyone else experience this? Not trying to start anything but from taking apart carbs (not too many, just a handful because I'm relatively new to the scene) even after about a year using regular 87 the carbs are really not bad at all. Having to clean carbs once a month due to 87 octane sounds like garbage  talk unless you're actually not riding but letting it sit...but even so, a month? Maaaybe yearly...? At TT mentioned if fresh gas is being run through the system and not being allowed to sit for a long time only the rubber bits are really affected.

You working for the oil companies?!?

...Understand that if the fuel is constantly flowing, being used and being replenished, only the rubber bits suffer.  If the fuel sits in the system for periods of time, that's when other compounds form in the fuel and attack/convert the metal parts.

Cheers,

---
1978 Honda CB550K

I believe around here (NJ) it's 10% ethanol. That's what they say anyway, I can't tell.

But I have the same observation, never had to clean up the carbs once they've been rebuilt and tuned so far, and that goes for bikes that sometimes sit for more than a month.

[flybox1]

@DaveBarbier  I run 87 (w/ ethanol) and have never had a 'varnish' issue.  I dont use any additives in my fuel either.
Sometimes I go several weeks between rides, and still, carbs are clean.

[70CB750]

Ethanol affects rubber pieces for instance.

[bjbuchanan]

... and builds up excess carbon from unburnt fuel over time

May I ask where you found that knowledge?

Higher octane fuel resists detonation for longer than lower octane. The whole point for using it right? When you use higher than necessary there can be excess carbon buildup due to an incomplete burn. You get an incomplete burn because that higher octane resists burning longer and your combination of spark and compression just isn't enough to expend all of what's in the chamber. It isn't as severe as a bad ignition system and the way that it can foul plugs but it is true for internal combustion engines.

As for ethanol:

I haven't seen any issues with my bike but it doesn't sit some ungodly amount of time. I have experimented and stuck away some fuel and it gets a different smell and appearance after a couple of weeks. I definitely have noticed that if you let it evaporate that you get that goopy, sticky crap that leaves people cleaning carbs. I guess don't drain them, leave them filled for storage?

My bikes don't sit enough to test it on the bike, I ride through the winter as long as there isn't a snow/rain forecast or its single digits.

[Deltarider]

Higher octane fuel resists detonation for longer than lower octane. The whole point for using it right? When you use higher than necessary there can be excess carbon buildup due to an incomplete burn. You get an incomplete burn because that higher octane resists burning longer and your combination of spark and compression just isn't enough to expend all of what's in the chamber.

I don't know where you learned all this but I can't follow the logic.

[edwardmorris]

Some good info and explanation in the link I posted above, delta.

[Deltarider]

Some good info and explanation in the link I posted above, delta.

Yeah, I know and...?

[70CB750]

Some good info and explanation in the link I posted above, delta.

Delta is a greenie, he will not accept logic or reasons that goes against his religion. If you feel like wasting your time, keep it up but it makes not sense or difference

[edwardmorris]

Some good info and explanation in the link I posted above, delta.

Delta is a greenie, he will not accept logic or reasons that goes against his religion. If you feel like wasting your time, keep it up but it makes not sense or difference

Its all cool Prokop  Don't feel like wasting time, neither can blame someone for their stance on something.