Leaded racing gas

Since unleaded pump gas can potentialy cause major gas tank and fuel system problems, would it be harmful to run pure 104 octane leaded racing gas? The cost is about twice premium unleaded gas, but over the long run, would the eventual costs of later repairs caused by damage from running today's gas balance out in a bike that is only driven on weekends? Or, are the concerns with today's unleaded gas overblown?
Thanks,
Ron

Commandos only got two issues on new non lead clean burn oxygenated-Alky fuels
1. Dissolves old school resin fiberglass that ruins paint and gunks up carbs engine.
2. Leaner burn may like a bit richer tune and one range cooler spark plug.

Norton factory seats tolerate no lead fine so your call to run no lead 104 which may give a bit less pow in response to the slower burn. Adjust spark time for this or put in higher CR pistons to get some advantage of 104 octane slower burn.

I've used blended leaded race gas with pump gas. The problem is where do you get the leaded fuel out on the road after the first tank runs out? I usually go through two to three tanks of gas per run.

I buy 5 gallons of leaded race gas at a time. Can't pump it into a vehicle's tank because it's not taxed like normal fuel. You can always keep a small bottle of octane boost or lead substitute on the bike for when you have to fill up on unleaded, but the ethanol is a whole 'nother problem, especially if you have a fiberglas tank.

illf8ed said:

I've used blended leaded race gas with pump gas. The problem is where do you get the leaded fuel out on the road after the first tank runs out? I usually go through two to three tanks of gas per run.

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British Only sells sell these small packets of octane enhancer that treats 2-5 gallons called Rocket Fuel. Part # 32-70140. Statement on back says it "helps protect pistons and heads. Aids valve & seat lubrication". Made by Cal Products. Boosts the octane 4-7 points. About $2.00 each. Small enough to store somewhere for those long road trips.

All this stuff is a waste of money on these bikes. There is no need for high octane fuel. NOTE that when octane boosters say they boost by 4-7 points it is NOT in whole numbers. For example, if you are using 90 octane gas and an octane booster advertises that it boosts by 6 points, it is NOT raising octave from 90 to 96. It is raising the octane from 90 to 90 POINT 6 (90.6). It's a meaningless addition even IF the engine had any use for for higher octane. There will be no performance increase with higher octane UNLESS ignition timing is changed (advanced). However, advancing the timing on a Commando to take advantage of true higher octane - like racing gas - means that starting will be much more prone to kickback...

Thanks for the responses. I am not trying to boost octane or performance, but to avoid using today's unleaded gas since from reading on this forum there appears to be some opinion that unleaded gas can cause problems. I just want to make sure that using the higher octane gas, without mixing, will not damage my engines. I only take short rides on weekends and buy the gas in 6 gallon containers.
Thanks,
Ron

lillygunny said:

Thanks for the responses. I am not trying to boost octane or performance, but to avoid using today's unleaded gas since from reading on this forum there appears to be some opinion that unleaded gas can cause problems. I just want to make sure that using the higher octane gas, without mixing, will not damage my engines. I only take short rides on weekends and buy the gas in 6 gallon containers.
Thanks,
Ron

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Ron,

With the exception of reported valve recession problems most of the problems cited with modern pump fuels is not due to the absence of lead. It's due to the addition of Ethynol. Ethynol attacks rubber components, disolves many of the linings used in fiberglass tanks, and reduces mileage.

I don't think regularly using leaded racing fuel is practical though. First it's illegal to use on the road as its price does not include road taxes. Second, you probably do not need the extra octane rating. Third, it's prohibitively expensive. Fourth, it's not easily found and can get you in trouble if the vendor sees you putting it into a road machine.

The most practical solution is to take protective measures for your machine and use readily available pump fuel; I recommend the lowest octane that your bike will run on without pinging (detonating). If you don't have a fiberglass tank, you have few worries with that. Replace your fuel lines with modern fuel lines that will stand up to the ethynol; watch your carb floats if they are of a 'plastic' composite; make note of valve clearance measurements before adjusting as an indication of valve recession (which is relatively rare). The changout of fuel lines and floats is far less costly than what you'll spend on fuel.

I run all of my vintage bikes except for one of my racebikes on commercial unleaded pump gas. I have experienced damage to a fiberglass fuel tank (now replaced with steel) and destroyed a pair of carb floats, but have not had the valve recession problems that many have reported. Other than that, my bikes have run reliably.

One man's opinion...just sayin...

I use castrol valvemaster octane booter in my Laverda Jota and it really transforms the bike. However you can improve the octane rating by adding small amounts of acetone, but if you think ethanol disolves fuel tanks acetone ruins fibreglass and takes the paint off steel tanks if spilt.
I ran an old Audi a few years back that would pink on acceleration and acetone cured it so it does work, and I got about 3 miles more to the gallon!

FWIW re acetone, go here, scroll down to "the Great Gas Conspiracy" http://kwc.org/mythbusters/2006/05/expl ... iracy.html

myjota said:

I use castrol valvemaster octane booter in my Laverda Jota and it really transforms the bike. ...

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Just curious what it was about the performance of your bike that was 'transformed' by increasing octane. Was it detonating prior to adding octane booster?

Acetone in fuel is an old trick to improve octane rating. It allows a few degrees more advance on ignition. I used it for 3 months and consistently got 3 mpg more than the preceding 3 months and lost 3mpg when I stopped using it! Worked on my merc 190E too but only 1.5 mpg. found that using small amounts ie 50ml in 12 gallons had no effect so upped dose in 50ml stages and found 200ml/12 gals best anything more actually reduced mpg. Got a diesel now thou!

"There is no need for high octane fuel."

Try getting a combat engine with a little carbon build up to run on even premium pump gas. My '72 needs a decoke every couple of years or it pings terribly. I would agree for 850s as they have a considerably lower compression ratio. I refuse to lower the compression on a combat engine. What's the point owning one if you can't enjoy the added performance. :wink:

lillygunny said:

Thanks for the responses. I am not trying to boost octane or performance, but to avoid using today's unleaded gas since from reading on this forum there appears to be some opinion that unleaded gas can cause problems. I just want to make sure that using the higher octane gas, without mixing, will not damage my engines. I only take short rides on weekends and buy the gas in 6 gallon containers.
Thanks,
Ron

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Back in the day, premium leaded fuel was the recommended diet for Nortons as well as all other motorcycles. There was no "ethynol" (actually spelled ethanol), a type of alcohol now commonly manufactured from agricultural products such as corn and added to most gasoline as an oxygenator, and normal compression ratios were a bit higher than what older-design combustion chambers could now tolerate with lower octane fuel. 100 octane was readily available at the pump. I always used Sunoco 260, the highest octane leaded pump gas available and anytime I had to resort to some lower-octane swill, performance suffered noticeably. The higher octane fuel used, the more spark advance and compression will be tolerated and the more power produced because higher-octane fuel burns slower and thusly does not tend to pre-ignite which saps power at the least and can cause engine damage at the worst.

So your motor will not be damaged in the least and if tuned correctly, will have more snap using high-test leaded. And your valves and seats will last longer although your sparkplugs will die sooner due to contamination from the lead.

Instead of expensive racing gas, you can get 110LL Avgas at your local airport. I got it for about $4.35/g in VA. So far that's what I'm using, but I don't have many miles on it yet. They seemed to be more than willing to sell it to me in plastic gas cans.

Dave
69S

DogT said:

Instead of expensive racing gas, you can get 110LL Avgas at your local airport. I got it for about $4.35/g in VA. So far that's what I'm using, but I don't have many miles on it yet. They seemed to be more than willing to sell it to me in plastic gas cans.

Dave
69S

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There was a story in CW about former EIC Dave Edwards putting Avgas in his new (to him) BSA Super Rocket ('65 or '66 IIRC) and ruining the motor on the way home. Don't know the specific reason, but I'd be wary of using it after I saw that. I know Avgas has anti-freeze additives to keep it from turning to jelly at high altitude where it's super cold.

I've read more than one thing that indicates Avgas is not good. I've got all winter to sort this out. Then too, I've read that people use it with no bad effects. I'd rather use regular (ethanol) gas, but my tank won't handle it right now. Thanks for the warning though.

Dave
69S

I'm using AVGAS 100LL, not sure what DogT has read that is anti AVGAS.

AVGAS has worked a treat for me, low lead is better than no lead ( with the cast iron head on the BSA ).

Not sure exactly why you would need to run leaded fuel in the Commando as the engine has an alloy head with steel exhaust seats ? ( I was under the impression leaded was used to stop exhaust valve seat errosion in cast iron heads, unless ofcourse if the exhaust seat inserts are cast iron ........).

AVGAS in Australia does not have anti icing properties/additives.

AVJET/JET A1 has the anti icing additives ( Kerosene used in turbo prop and jet engine ).

The head material is irrevelant. More important is the valve and seat material. Leaded fuel lubricates valve seats, but newer motors designed to run on unleaded have seats and valves made of much harder material than older motors. Valve seat recession is accelerated without lead in older motors. They'll still run, they just won't run as long before valve clearances disappear. Before you run completely out of adjustment at the exhaust valves, the valve spring assembly will attain too much assembled height and valve seating will become sketchy due to lost spring pressure. Then the drill is to take the keepers off, remove the springs and ad shims at their bases to attain proper assembled spring height. It can be done with the head in situ on the motor in the frame by pressurizing the cylinder with air at the spark plug holes to keep the valves from falling into the head until reassembly is accomplished. Personally, I'd rather add some lead or use leaded fuel if possible.

I did a google search on 110 LL Avgas and I got a bunch of opinions. No science. Most seemed to complain about the lead gumming up things or ruining the O2 sensors and cat converter which we don't have to worry about. I doubt if it will be a big issue to me. I've had others on the forum tell me not to use it, and others like Josh, use it.

Dave
69S