Gas grades

[apopleptic]

My 1980 GS450 says to use 90+ octane. I usually get super (91 octane)
I know when I drive across the country in my car I buy whatever the cheapest grade is and I get quite a bit better mileage with 85 octane instead of 89+, but the regular they sell around here (PA) is 87 which seems to give me the worst mileage of all.

[koolaid_kid]

s

My GS always rattled (ping, pre-ignition) on 87. In any state I went, any brand, rattle. She never rattled on 92+. And the timing was not adjustable, so I was stuck. It really sucked when we pulled into some tiny town that only sold regular. I was stuck with the rattle.
After I installed the Dyna S, she seldom rattles on 87, so that is what she gets. Of course, I set the timing by hand, so I know it is close to perfect.
The GPz, well, is a bit different.
IMHO, every single engine is a bit different. Find the sweet spot for your particular engine by going down in grade until the bike rattles. If you don't get rattles on 87, use it. If you do, move up incrementally until it goes away.
This only applies to stock engines, of course. Modified and FI engines are a different story.

[bccap]

I was running 87 in mine until dechand43 posted this;

I have read quite a bit about "brown talcum powder type stuff" in carbs by people who think it's rust. It is NOT rust! I build bikes, and also work on boats, and this stuff showed up heavy in the fuel tank of one of the boats I worked on. Trouble was, the tanks were stainless steel, so this stuff could NOT be rust. I had to find out what it was and the results are in, after a LOT of research!
It seems that ethanol reacts to oxygen, and the resultant residue is the byproduct of the breakdown of the ethanol. It begins in around 90 days of sitting in the tank untreated. It sticks to the insides of the tank and then flakes off, in the consistency of talcum powder, and will go through regular fuel filters like they weren't there. To catch it requires a 10 micron or smaller filter. It loads up beneath the pilot jets and makes it nearly impossible to "dial in" the carbs to idle right. "Kreem" can help immediately to seal it off, but if ethanol fuel is left sitting in there untreated it will foul that too. It does come off the inside of the tank when the tank is "banged", much heavier, making people think it is surface rust knocked loose. Two solutions I have found;
Buy non-ehtanol fuel(fat chance here in the US, They actually want to pass laws to make the content 20% instead or the present 10-15%).
or;
TREAT the fuel with additives sold everywhere.
Otherwise you will just have to ride hard and a lot so the fuel never gets old! ;-} I know, a third, sorry but I just had to put that in since it is my personal solution.
I bought a PAIR of GS850G's for 460 bucks and found this stuff in them. The first one I got running (and put 8K miles on in the first 7 months I had them) had this stuff under the rubber plugs that the pilot jets live under in the CV32mm carbs, and it has been one hell of a "chase" getting it cleared out!
If you have to leave the bike sit for more than a very short time, treat that fuel. Carb cleaner does not clean this stuff up either! The prep chemicals used for preparing the inside of a tank for "Kreem" works though.
Just thought I would pass this along. Can't fight what you don't understand, right? :-}

I switched to premium and noticed the bike running smoother and quieter.

[kingofvenus]

My '83 has a shaved head and five degrees advanced timing, and it still runs great on regular.

[kingofvenus]

I do agree that the "corn gas" as i call it sux, i try to not use it if possible.

[Dakotakid]

(Rolling eyes)...I run nothing but 10% ethanol in my GPZ 750, GS 850, and both Yamaha 500's at 88 oct. They run GREAT and I have no ill effects...no tank rust....no deteriorating rubber in the carbs.....just good power. Only once, in 100 heat, at 5000 feet elevation, on a long up-hill did I get the GS to lightly ping.

I realize a lot of you guys idolize Dick Cheney...but, I don't and I run lots of ethanol. I actually run at least 50% booze in my fuel injected VW gas rigs and life is great! Been doing it for years. Be careful whose gas you whiff!!!!!!

[81GS750]

Regular unleaded in all my bikes except for the turbo Yamaha, it get premium.