I have always run 91 octane plus because thats the only way to get it around here without ethanol. Ethanol is evil to you carbs!

 

the octane ratings are calculated differently in NA compared to Europe. Ours is the R+M/2 method (R = reserarch, M = mechanical). I think ratings semantics aside, the "true" octane ratings (as a resistance to detonation) are very close (ie. our 87 would be close to your 95, or whatever your "regular" is rated at).....

 

Some years ago, someone did a dyno test on a snowmobile engine (carbureted, liquid-cooled two stroke 700cc twin) that was rated for 87 octane. Switching to 91 octane (no changes made) resulted in a 2 hp loss........ again, it is generally recommended that one use the lowest octane rating that will maintain detonation protection, and get the best performance (and cheapest operating cost).....

 

Actually, the European 95 RON ratied fuel is actually equivalent to the US 90.7 AKI rating for octane content... But in Europe it's almost always 5% Ethanol content (95 e5), altough 10% variations are popping up... But so far the "premium" 98, is still 5%, so running that might have advantages...

 

here is another article on gas but this time as it pertains to motorcycles.
they refrence a katana for a lot of it and talk of compression ratios.
Katana is 600cc with a compression of 11.3:1 ~65HP said to be a de-tuned gsxr motor.
As most here will know
VTR is compression of 9.4:1 HP ~ 103HP

Understand Motorcycles & Fuel Octane Numbers

 

I remember reading 4 cylinder engines are less likely to ping due to smaller pistons for a given cc compared to a twin or single.

 

Looking at sticker on bike it reads Gasoline 91 RON

[/IMG]

 

Which is 86 octane in US I do believe.

 

Sticker under the seat reads Gasoline 91 ron.
Reading on wikipedia it says that MON is always lower then RON, so 87 R+M/2= will always have a 91 or greater ron rating (see wiki for table).

Ethonal will not hurt your hawk!
from the owners manual (pg 36)
Petrol containting Alcohol
if you decide to use a petro containng alcohol (gasohol), be sure it's octane rating is at least as high as that recommended by Honda. There are two types of "gasohol". one containng ethanol, and the other containing methanol. Do not use petrol that contains more then 10% ethanol. Do not use petrol containing methanol (methyl or wood alcohol) that does not also contain cosolvents and corrosion inhibitors for methalon. Never use perol containing more then 5% methanol, even if it has cosalvents and corrosion inhibitors


So ya Honda says 87 (usa, canada) is what is needed!
Ps. I'm still running 91..

 

I frequently do the same. Just don't trust the ethanol. Not because it will damage the engine, it won't. My bike has to sit for 2+ months at a time without being ridden. I use Stabil but I think it works best with no ethanol fuel.

I have a Yamaha 2stroke outboard and the carbs are really sensitive to fuel sitting in them. So I use the no ethanol fuel in them. Most of the marinas in my area have no ethanol gas and there are several local gas stations that at least have no E premium. Anyway, the outboard cautions have spread to the bikes.