Bad Gas?

[gack]

I filled up with 91 octane, full tank and the bike ran fine but when i re filled with the same octane gas the bike ran like crap with no power and felt like a bad miss with any throttle. I usually just run 87 octane and have no issues with it, it usually runs smooth with the power you would expect all the way to red line. I had the same thing happen last year and it was again on the second tank that the issue popped up. I pulled the gas out and replaced with 87 and once the 91 was used up in a few miles the bike instantly ran like it should. my question is, do you think this is a case of bad gas and its just a coincidence that it was on the second tank both times or does it sound like it's a case of plugs, valves or something else.
bike is a 2002 40,000km. don't have any history before 28,000 km so might have the original plugs and no idea if the valves have been looked at. Also the bike feels twitchy at low rpm with the 91 where its smooth with the 87. I'm of course fine running the 87 but just curious if this is a sign of a problem. I'll probably change the plugs and adjust valves anyway but don't really have the time right now.

[CBXRider]

I've always run 89 octane fuel in my 06 with never a problem over eleven years and 60K+ miles. IMO, the octane is too high for the present tune, plugs etc.

[Bailey9r]

Happened to me once and drained the fuel and it was about 40% water.

[Popie]

Probably just some bad gas. My 04 runs fine on 87 or 91. The only difference I see is the cost...
I do avoid ethanol. But I know in some parts of the country you're stuck with it.

[gack]

Thanks for the replys. I'm pretty happy with the way it runs on regular and like you say popie it's cheaper. I might try a little high test from another gas company just cause I'm curious.

[HoboJoe]

This post caught my eye since after 25yrs of hauling it around I know something about it. There is no such thing as Bad Gas, per se. Only a glitch in the supply/delivery/maintenance chain. When people found out I hauled it they would always start asking questions. Told them all the same thing. Try to get your gas at the same place, use a major brand, and use the recommended octane. If for some reason you can't for once it really ought not to be a problem. There are some variables of course but they are to numerous to list in this format. With the limited info you provided it's hard to tell. But don't cheap it. You're not accomplishing anything. The same people that drive across town to save .03 a gallon are the same people that won't make that same drive to save $20.00 on a suit......Go figure

[jellyrug]

I thought someone ate too many beans......

[gack]

Thanks for the info HoboJoe, I buy from one of two major gas stations that have large turn over and stay away from the cut rate guy's. And when I say bad gas, I would expect that it would be a maintenance issue with the station as opposed to something from the supplier,

[RedBusarider]

I try to always buy TIER ONE gas.

Mobil/Exxon is one supplier that is Tier 1.

I also have never run anything other than 87 in my Busa.

[gack]

I try to always buy TIER ONE gas.

Mobil/Exxon is one supplier that is Tier 1.

I also have never run anything other than 87 in my Busa.

Yep. I've learned my lesson. I don't see a point in running anything else. No water what my mechanic buddy's say. Lol.

[CBXRider]

All underground fuel tanks contain water. Fueling up while the trucks are refilling them can be risky as it stirs up the water. Wouldn't make a lot of difference in a car's tank but in a tiny motorcycle tank it could mean real problems.

[nosbig]

Even at the best gad stations you can get bad fuel. The local Marathon station here had an incident about six month ago where the delivery guy accidentally topped off the 87 tank with diesel fuel. The station did the right thing and took responsibility, but never the less it happened.