Gasoline

In my opinion, although not ideal, E10 won't do damage as long as you keep cycling fresh E10 into your tank, in other words, you want to be riding enough that you are regularly refueling, and you aren't letting the E10 sit for a long amount of time, like 6 months. If you are going to let it sit, then use an ethanol stabilizer and run the carbs dry.
As for which is better, non-ethanol 87 or 91 E10 -- I dunno...
 
Well, you’re engine isn’t going to be damaged just because you run a lower grade fuel. Incorrect jetting and timing being off will do way more damage than gas choice, and all three together will be a problem. Higher octane is better, but If you’re somewhere and they only have 87, there isn’t going to be huge repercussions for it. Just don’t beat the hell out of the motor as much. I wouldn’t stress about it

Also use the search bar. There are a significant amount of threads on this topic already and have been talked about in more detail
 
The damage potential for low octane fuel is simple. It is more prone to detonation, and the purpose of raising octane level is to slow flame travel to impede detonation and prevent holed pistons (it has nothing to do with increasing energy.) Serious risk of damage to the motor occurs in very hot environments, when vacuum leaks develop and cause a lean A/F mix, and, on bikes with breaker point ignitions, when wear in the advance governor (AKA "Automatic Timing Unit") stretches the advance curve and opens the points well before the factory max advance of 40* BTDC (many of us, self included, set timing to a max advance of 38* to 36* BTDC). While high octane fuel doesn't guarantee that your pistons will never suffer ventilation, it's damn cheap insurance.

Nonethanol gas is no longer available in my area, and hasn't been commonly available in Illinois for decades. Our old bikes haven't suffered much for it; just drain carbs and tank for long storage. Years ago Rex Blanchard gave a tip on this board that I found very useful: Stabil marine formula keeps 10% ethanol gas from going bad much longer than standard fuel stabilizers and makes it safer to use in 2-stroke motors. I use it in the fuel for my 4-stroke Yamaha if it's going to sit awhile (after draining the carbs), and in all my 2-stroke power equipment, including a chain saw that's held up for 16 years.
 
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The marine folks have it figured out; you can generally find non-ethanol at higher octanes around popular boating locales. In AZ mostly Havasu, also Flagstaff (elevation ?)

Any state's list here https://www.pure-gas.org/
 
Those pure-gas local listings used to be too often obsolete to be useful in this area, but they seem to have gotten more serious about updating, and I see a few in reasonable distance that I'll call before driving out. Thanks for the reminder to look to that site, JP!
 
The site actually went down for awhile - claimed lack of support. Perhaps they shook the tree and the green fell.

BTW - I've been impersonating a carb expert this evening on another thread - maybe you can help....
 
I called a few of the stations on PureGas in my area, that are about an hours drive. Some had no idea what the difference was between 87 and 91 octane. Some said yes we have 91 octane without ethanol. Road trip in order with fingers crossed. Based on all the info on this thread and on this site I'll go with 91. Preferably non ethanol. 91 with ethanol with stabilizer is second choice.
 
Had a look, not much to add. It's all been done and written before many, many times, and I don't have much patience for guys who have the time to write a book on a common, simple problem but can't seem to find time for a few simple searches that would take less than half the time and effort required to tell their tale of woe. I find it suspect that the poster either has enough experience or has done enough reading to understand the operation of vacuum diaphragm systems and to do a carb rebuild that includes replacement of throttle shaft seals (no rookie task, that!) but does not own a timing light and claims to be unaware of what's making the idle spike. The Carb Guide has a fine section, written by 5twins, that covers jetting for mods, and I seem to recall writing detailed instructions on mix screw, synch, and throttle stop adjustment; whichever coauthor wrote those particular bits, it's all there and I don't have enough time left on the green side of the grass to write it again for somebody who won't spend a fraction of the time and effort I'd have to waste. If he'll push the Tech button and scroll through a few menus he'll find what he needs if he has a longer attention span than a gnat and the patience to read. Two things only to add. First: Is the original breaker point ignition still in place? If so, does the advance rod move and return freely on an unfired engine, cold and warm? Was throttle plate alignment in the venturi checked? That wouldn't be a direct cause of the idle spike, but could create other issues going forward.
 
Yes sir, I'm a newb here and currently enjoying the problem solving journey. I'm in awe of ya'll that have been on these boards over ten yrs and still sharing - understood.
 
You're the victim whose time is being burned here, JP. The culprit is the attention seeker who sucked you into his drama. Sorry, I'm feeling more crusty and intolerant than usual, but a twerp in Carbondale on this board has already taken unpaid time from an old friend of mine who runs an independent shop on a tight budget and really can't afford to give his time away to deadbeats, but keeps doing so out of the goodness of his heart. He's literally living in poverty as a consequence. I keep telling him that when one of these cases comes in the door he needs to say "Stop right there. I charge $200 up front for diagnosis and estimate, and I'll make notes as soon as you pay in cash." Dammit, he's not out a cent if a deadbeat walks away! He won't do it; he's one of the few out there who is consistently generous to the point of self harm.
 
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