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Finally put on enough miles to find what grade my 700 likes best, she likes mid grade (89 octane) runs the best unlike my CB750 that loves premium.
 

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If your engines require a higher octane than the required 87 then you may have an issue. What was your experience with 87?

G.
 

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It runs fine on 87, but I have removed the stock air box and filter and using a high flow filter plus larger jets and better flowing exhaust, so it's getting a bit more air in the cylinders at WOT.
 

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If you were not experiencing knocking/pinging then you should stick with 87. If you were experiencing knocking/pinging then a higher octane is a temporary "fix". High flow filter, jet and exhaust don't require a higher octane unless you have somehow increased your compression ratio. Even the more recent engines can use a higher compression ration but require a PGM-FI and ECM that handle the lower octane. ie Gold Wing has a 10.5 compression ratio and recommended PON is 86.



G.
 

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Well I like the original poster know my bike better than most here. My stock 06' 1100 Spirit ran best on 89 octane for 35,000 mi. Now the the Valk just loves 87 octane as recommended. The Vulcan 90 as recommended.
 

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My 2000 Spirit VT1100C calls for 86 or higher.

I have a 99 and I run boat gas, think it's 87 octane no ethanol. Bike runs better on that than higher octane ethanol gas. Bike has a low compression ratio so high octane shouldn't do anything for the engine. Ethanol doesn't have as much power for volume compared to gas and in theory it really shouldn't be noticeable but I can notice the difference. After market exhaust and K+N filter, rejet as well. That shouldn't matter octane is all about compression. More air and more fuel doesn't change the compression.
 

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91 octane is how I avoid ethanol gas in Ontario, Canada. (-:
My bike runs on 87 but it worries me for sustained highway use as I run a bunch more ignition advance than stock, at higher engine speeds and it has a Bean Box style intake.

When you come right down to it the static compression ratio is merely one factor in the peak pressure developed from combustion.
Modern internal combustion engines are subject to dynamic flow considerations and it is conceivable that with a more open intake and exhaust it will stuff more mixture into the cylinder at higher engine speeds, therefore creating more peak pressure and a power increase that goes along with it. If you are seeing a performance increase with your changes that is where it is coming from and that may be why it seems to have a preference for higher octane fuel.

As with everything else check the spark plugs after a hot fast run on each fuel and see what they tell you compared with a plug chart, with too low an octane rating you may see signs of overheating and at the extreme end of things aluminum flecks on the insulator or a broken insulator.

Ask any 2 stroke racer you happen to see and they will tell you things can go south fast with no clacking ping noise warning like a '60's muscle car on regular.

If people would leave these things alone they'd go just like Honda intended. (-;
 

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Anyone have a recommendation for a 2018 750? I’ve had it for a few months and have been putting in 89. Manual says 87 or higher. I thought I read somewhere someone suggesting 89but after reading this post I’m not sure
 

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Anyone have a recommendation for a 2018 750? I’ve had it for a few months and have been putting in 89. Manual says 87 or higher. I thought I read somewhere someone suggesting 89but after reading this post I’m not sure
Just what the manual says 87 or higher should be fine.
89 is fine but more expensive than 87, Honda knows what they are doing.
 

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Short chem refresher: octane rating describes the fuel's reluctance to ignite under pressure

(how well it will avoid premature ignition from residual heat in the cylinder during the compression stroke).

It has nothing to do with power.


gasoline is a mix of C5-C12: pentane, hexane, heptane octane, nonane, decane, undecane, dodecane, and many isomers of these.
straight chain heptane (C7) has an octane rating of 0, Trimethylpentane (iso-octane) has an octane rating of 100.

and ethanol actually boosts the octane rating of gasoline by making it more reluctant to ignite compered to heptane.
 

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Short chem refresher: octane rating describes the fuel's reluctance to ignite under pressure

(how well it will avoid premature ignition from residual heat in the cylinder during the compression stroke).

It has nothing to do with power.
That is the basic truth.
A lot of people think using a higher octane rating will increase power and in some cases it might actually reduce power.
There is no benefit to using higher octane rated fuel unless specifications or modifications to the engine require it.
Effectively more power, more pressure, more heat requires less easily ignited higher octane fuel.

Now as I understand it in my particular City, gasoline comes in and it is all the same stock and then at the facility here different additives are blended in to suit manufacturer/branding, octane rating and climate conditions. Now the strange thing that occurs here is that in this part of Ontario, Canada is that for most retailers Regular 87 octane gas contains up to 10% ethanol, 89 up to 5% ethanol and 91 and 93 octane rated gas is ethanol free. This seems counter-intuitive I have been told this is all driven by politics and the cost of fuel additives.

There is another anomaly which doesn't effect Honda Shadows AFAIK, where higher octane rated fuel will make higher power in some current modern fuel tolerant, relatively high compression engines, where a multitude of sensors feed information to an Engine Control Module which can control the ignition timing, valve timing and fuel delivery.
 

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Thinking 87 with Seafoam now and again.Put some kind of weird Mobil Supreme (3.59 Gal,too much for my blood) in other day think it was 91,supposed to clean fuel system.Ran just fine.
 

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If I could by 91 octane with no ethanol I would get it if it were reasonably priced. Higher octane doesn't hurt anything other than your wallet. I ran 91 octane forever in a TW200 and it never hurt a thing. Then gas prices tripled and I started using the lowest cheapest octane available. I have 45,600 miles on this bike with no overhaul and it is still running great. I have noticed a lower octane quicker burning fuel gives me a little more top end speed but I do burn more gas.
 
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