Octane rating for Nortons?

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APRRSV

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I have read many posts concerning alternative gas (petrol) options for Nortons. but I have a few questions concerning what is good and what is not good.

1) We have available 93 R+M/2 non ethanol fuel.

2) We also have available non-ethanol Sunoco Racing Fuel. The R+M/2 octane ratings vary from 95 to 112 (unleaded and leaded). Surprisingly the higher octane ratings (leaded) are less expensive than the lower octane unleaded.

So my questions are:

a) Is 93 R+M/2 octane non-ethanol suitable for 10:1 CR?

b) Is there any danger with using 100+ octane fuel (leaded or unleaded) in our Nortons (other than the legality of using leaded fuel)?

Thanks,
Ed
 
APRRSV said:
I have read many posts concerning alternative gas (petrol) options for Nortons. but I have a few questions concerning what is good and what is not good.

1) We have available 93 R+M/2 non ethanol fuel.

2) We also have available non-ethanol Sunoco Racing Fuel. The R+M/2 octane ratings vary from 95 to 112 (unleaded and leaded). Surprisingly the higher octane ratings (leaded) are less expensive than the lower octane unleaded.

So my questions are:

a) Is 93 R+M/2 octane non-ethanol suitable for 10:1 CR?

b) Is there any danger with using 100+ octane fuel (leaded or unleaded) in our Nortons (other than the legality of using leaded fuel)?

Thanks,
Ed
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Yes 93 should be fine. That is about 99 RON.

Octane rating for Nortons?


Octane Redux

I came across this snippet of an article at http://www.faqs.org/faqs/autos/gasoline-faq/part3/ "6.3 What fuel property does the Octane Rating measure? The fuel property the octane ratings measure is the ability of the unburnt end gases to spontaneously ignite under the specified test...
www.accessnorton.com www.accessnorton.com
 

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My buddy has a 72 Combat Interstate and he says that anything less than 93 (US number) will make his motor ping. 93 is the standard "premium" pump gas here, with E-10.
 
Most readily available octane rating here in Canada is 91. That is what I run my Combat on. I have to run it a little on the rich side to keep pinging in check.
 
I do a mix of 104 octane aviation fuel and 89 octane non-ethanol. 50/50 mix Everything seems to love it. My 961 loves straight aviation fuel!!!
 
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My owners manual say 100 oct , like previous poster I mix non ethanol 91 with leaded race gas to get close to the 100 , this can I have now is 114 so 50/50 seems to be working very well …
 
My old 850 does great on the 93/ ethanol pump garbage here. Lord! Don't try to feed it the lower octanes containing ethanol or it sounds like marbles being shaken in an old coffee can. It does accept 89 non ethanol with some slight protest though.
There was noise of raising the ethanol percentage a couple of years ago in pump gas. If that comes to be then I don't know what'll happen..... Probably have to buy race gas to survive should it actually happen
 
I can't tell if mine pings or not. The symphony of noise coming out of it is difficult to decipher. So I'm going to run down to O'Reily auto parts today and get some of their inexpensive octane booster and pour it all in my small tank to see if it sounds any different. If it does, I'll know it needs more octane than what is in Seattle area pump gas. Pump gas in the Seattle area is maybe 91 octane. That is what I run in it. With the pumper FCRs I don't hear anything odd under acceleration, and it doesn't lack for power, but like I said can't tell for sure if it pings or not. If it does, it's very mild, and not very ringy dingy.

The book I have does say to use 100 octane, anything less may cause engine damage. I'm sure it would run better if I had a time machine and could go back to whenever pump gas was 100 octane. In the meantime, I'll use the octane booster.
 
Thanks Les , never to old to learn , either way, my mix keeps plugs looking right and the old bike breathing fire !
 
For any given octane rated fuel, combustion conditions depend on comp. ratio, fuel mixture and ignition advance. If you don't change your jetting, increasing the comp. ratio or advancing the ignition timing will have the same effect as leaning-off your jetting. Amal carbs use 0.106 and 0.107 inch needle jets, so most are probably jetted slightly too rich. When you increase the comp ratio or ignition advance with high octane fuels , the better performance probably comes from the leaning-off effect. You might get the same effect without those changes, if you simply used better carburetors or fuel injection with low octane fuels.
In the 1950s, most Australian road racers such as Eric Hinton, used methanol fuel in their Manx Nortons. When the guys got to Britain, the found the Poms could get their Manx Nortons going just as fast, using pool petrol. Methanol hides up the tuning errors and has unlimited anti-knock. Poms play cricket - jetting a GP carb on petrol is the same deal - boring. To get a petrol motor jetted right using Amal carbs, you need a lot of patience. Then the motor's performance becomes more weather-dependent.
 
Craig said:
Thanks Les , never to old to learn , either way, my mix keeps plugs looking right and the old bike breathing fire !
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I only ever use plug readings to set my main jets and to make sure I am not burning anything. Mid range jetting ( needles and needle jets ) is much more important, and plug readings don't help with that. The problem is that slightest bit of over-jetting in the mid-range appreciably slows acceleration when you ride the bike, but the bike still feels fast. If you get it right, then you discover the difference. But for a road bike, you are probably better-off running slightly too rich, because cold weather causes further leaning-off. If your bike really flies when the weather is extremely cold, it is probably jetted too rich in the midrange. My main jets are always too rich. It is unusual to start burning valves or pistons at anything less than full throttle. Fitting a megaphone exhaust to a correctly jetted motor will do it.
 
Schwany said:
I can't tell if mine pings or not. The symphony of noise coming out of it is difficult to decipher. So I'm going to run down to O'Reily auto parts today and get some of their inexpensive octane booster and pour it all in my small tank to see if it sounds any different. If it does, I'll know it needs more octane than what is in Seattle area pump gas. Pump gas in the Seattle area is maybe 91 octane. That is what I run in it. With the pumper FCRs I don't hear anything odd under acceleration, and it doesn't lack for power, but like I said can't tell for sure if it pings or not. If it does, it's very mild, and not very ringy dingy.

The book I have does say to use 100 octane, anything less may cause engine damage. I'm sure it would run better if I had a time machine and could go back to whenever pump gas was 100 octane. In the meantime, I'll use the octane booster.
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I ran 92/3 in Seattle for almost 20 years before I moved to NZ. All it did was wear out a soft lobed cam. Guys at Pokes told me not to use octane booster. Can't recall why.
 
gortnipper said:
I ran 92/3 in Seattle for almost 20 years before I moved to NZ. All it did was wear out a soft lobed cam. Guys at Pokes told me not to use octane booster. Can't recall why.
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If your motor has been pinging while you have been riding it regularly and often, you should know about it by now. If it is that lean, you would be burning valves and pistons. When you ride your bike, it should never cough as you wind the throttle on. If the motor pings, you have gone miles too far in leaning-off the jetting. I always keep the fuel type, ignition advance and comp,ratio constant, then jet to that combination.
 
acotrel said:
If your motor has been pinging while you have been riding it regularly and often, you should know about it by now. If it is that lean, you would be burning valves and pistons. When you ride your bike, it should never cough as you wind the throttle on. If the motor pings, you have gone miles too far in leaning-off the jetting. I always keep the fuel type, ignition advance and comp,ratio constant, then jet to that combination.
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It was never lean.
 
I'm trying to envision Amal's + Commando = lean mixture when there's fuel in the tank. Just pondering out loud and not trying to sound facetious. Maybe I'm tattling on mine.... After the many years we've been together my plugs have only now reached a faintly tan hue with mucho carb/jet/adjustment/$ piddling. But spits back until up to temp, so as long as fuel remains unchanged I'm good using the summer blend produced here.
Don't know if the blend changes seasonally in the UK, Au, or EU but its done here and affects my old motor requiring piddling when its done. It is noticeable.....
 
Plug colour does not mean much. With road going Commandos, two main jets are specified. I would just fit the bigger one, then do a run at full throttle and do a plug chop. There should be a 3 mm black ring on the plug's porcelain insulator, right down inside where it meets the metal. The rest is about needles and needle jets. Even with the leanest taper needles, if you lower them until you get the cough when you ride the bike, then raise them one notch, you will be OK.
When setting the main jets, if you use the next hotter heat range in spark plugs for tuning, you will stay safe. My main jets are a bit richer than they need to be. When I am on full throttle my motor is not running at the extreme. To me acceleration as I wind the throttle on is more important than what the motor is doing when I am flat chat. With methanol fuel, a bit rich at full flight does not matter. But in the mid-range, it is just as critical as petrol.
 
gortnipper said:
I ran 92/3 in Seattle for almost 20 years before I moved to NZ. All it did was wear out a soft lobed cam. Guys at Pokes told me not to use octane booster. Can't recall why.
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Pokes may have told you not to use octane booster because it doesn't make a lot of difference based on the test ride I just took, and it may have been hard on Amal carburetors. Pure speculation of course.

The O'reilly octane booster I picked up smells a little like kerosene. I wasn't expecting that odor. Race gas makes a difference I could always feel, and it smells sweet to me, but I have to drive too far to find race gas around here. If it were closer I'd probably blend it with the pump gas once in a while. I use to get race gas in 60 gallon drums and run it in my off road toys. That was a while ago though. I think it was <$2.50 a gallon then.

I just checked my plugs to see if the octane booster left anything behind like flakes. Nope. I'll use up the rest of it without worrying about it. I bought 5 bottles of the stuff, and have other 4 wheel vehicles I can run it in.

Speaking of plug readings. My plugs currently only have a hint of tan on the porcelain. I've ridden it more than 1100 miles with the plugs reading like that. Prior to getting my electrical system completely squared away (for now anyway), my plugs were on the very dark side for 6800 miles. I thought my motor was getting tired, but the plugs look like they came out of a fresh motor. Amazing transformation. Must be a harbinger of impending doom. :)
 
Schwany said:
Pokes may have told you not to use octane booster because it doesn't make a lot of difference based on the test ride I just took, and it may have been hard on Amal carburetors. Pure speculation of course.

The O'reilly octane booster I picked up smells a little like kerosene. I wasn't expecting that odor. Race gas makes a difference I could always feel, and it smells sweet to me, but I have to drive too far to find race gas around here. If it were closer I'd probably blend it with the pump gas once in a while. I use to get race gas in 60 gallon drums and run it in my off road toys. That was a while ago though. I think it was <$2.50 a gallon then.

I just checked my plugs to see if the octane booster left anything behind like flakes. Nope. I'll use up the rest of it without worrying about it. I bought 5 bottles of the stuff, and have other 4 wheel vehicles I can run it in.

Speaking of plug readings. My plugs currently only have a hint of tan on the porcelain. I've ridden it more than 1100 miles with the plugs reading like that. Prior to getting my electrical system completely squared away (for now anyway), my plugs were on the very dark side for 6800 miles. I thought my motor was getting tired, but the plugs look like they came out of a fresh motor. Amazing transformation. Must be a harbinger of impending doom. :)
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Small and Son in Auburn can tell you where to find it.

Race Fuels - Small and Sons Oil Distribution Company

Race Fuels -Small and Sons Oil offers race fuel products and race fueling services for our customers in the Seattle Tacoma and Greater Puget Sound Region.
www.smallandsonsoil.com www.smallandsonsoil.com
 
FWIW, running 89 non-ethanol in my 74 Mk2 - cant say i've noticed any pinging or problems. some may have issues for me though....
 
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