Aviation Fuel

Topics related to the ownership, maintenance, equipping, operation, and riding of the R1150R.

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Bogdan
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Aviation Fuel

Post by Bogdan »

My youngest son was in the process of buying his first motorcycle. One of the bikes he looked at was a 4 cylinder 600 Honda Standard - maybe 15 years old; it was a carbureted model. The bike was very clean and the price was right. However....it didn't idle evenly. The owner monkeyed with the carbs and still couldn't get it to idle right. The owner was also an airplane enthusiast - in fact the bike was kept in an airplane hanger. He mentioned - as a positive - that he routinely filled the Honda with high octane airplane fuel. I think avgas is 100 octane. I wondered if the extra alcohol in the fuel was more than ideal for a motorcycle and compromised the soft parts in the carbs ? What do you guys think ? FWIW son Teddy ended up buying a 2 cylinder Kawasaki Ninja 650; he loves this bike. I taught him how to ride on my KLR 650 - perfect for learning on - as dropping it is a non-issue.
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Photoguy
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Re: Aviation Fuel

Post by Photoguy »

The only thing I know about avgas is that I used to use it in my trials bikes without issue. It was recommended when I first got into trials and was relatively convenient to get so i just kept using it. I think the recommendation was due to the engine's higher compression ratio...but it's been a long time and I don't remember much else about it.

But to your question, I used it over years and years and never had any carb issues with the off the shelf Keihin carbs that these bikes (GasGas) came fitted with.
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Re: Aviation Fuel

Post by towerworker »

I've no direct experience but I think CycleRob does. Seems to me aviation mechanics might have been a part of his past. Maybe he'll join in.
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Re: Aviation Fuel

Post by Barista »

Av gas won't hurt it, and it doesn't normally have any alcohol. Octane is simply a rating of the speed at which fuel burns. I've used av gas in everything from a lawn mower (when that's all I had), to my 1970 Chevelle and they all love it. The biggest problem with alcohol in gas is that alcohol will absorb moisture from the atmosphere faster than petroleum which can be a problem for vehicles that are stored for long periods of time. BTW - Alcohol does not deteriorate plastic parts. That's a common misconception.
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PeterNuss
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Re: Aviation Fuel

Post by PeterNuss »

There's no alcohol in 100 LL avgas by regulation. What's in there is 5 times the amount of lead that was in leaded gasoline used by cars years ago. A better mix would be 50% avgas and 50% unleaded fuel for older motorcycle use in off road conditions. If you use it in anything with a cat, well, that would be pretty bad for your wallet
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Re: Aviation Fuel

Post by AZBMWRIDER »

I was born and raised in the Chicago area, to the best I can remember ethanol was added to the fuel supply around mid '70's, I think it was 5% then .
I never saw any negative aspect to alcohol on a vehicle, except loss of fuel mileage .
I'm an aircraft mechanic for an airline, early on in my career, I worked on helicopters .
First thing that was done to the helicopter before a heavy maintenance check, was to drain all the fuel out of it, after it was removed, it was considered contaminated and could not be put back into the helicopters .
The recip engined helicopters had 100 LL (Low Lead ), for about a year I never purchased fuel for any of my bikes or car .
Currently the only down side to using avgas today , is that if you have a vehicle with a catalytic converter, the lead content of the fuel will damage the converter .
Up until a few years ago, motorcycles in the major metro areas of Aridzona, needed to go through exhaust emissions as part of the vehicle registration process .
We've had 10 % ethanol in the fuel supply here in Phoenix, for about 15 years, have not seen and detrimental effects on any of the bikes or cars, except a noticeable drop in fuel mileage .
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Re: Aviation Fuel

Post by riceburner »

Barista wrote:Av gas won't hurt it, and it doesn't normally have any alcohol. Octane is simply a rating of the speed at which fuel burns. I've used av gas in everything from a lawn mower (when that's all I had), to my 1970 Chevelle and they all love it. The biggest problem with alcohol in gas is that alcohol will absorb moisture from the atmosphere faster than petroleum which can be a problem for vehicles that are stored for long periods of time. BTW - Alcohol does not deteriorate plastic parts. That's a common misconception.

Point of note - it's ethanol that's used to decrease the price of fuel, not alcohol. They're two different chemicals and have different affects on certain types of rubber. (again, different rubbers suffer differently - chemistry is a wonderful science).

Re Avgas, or high octane fuel - it burns slower than lower octane fuels, and thus is better for high compression engines as it doesn't 'pre-detonate' - ie burn before it's meant to.

* NB: all the above is as I remember my basic engineering-science - I might be off slightly, but I believe my 'gist' is correct.
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Re: Aviation Fuel

Post by kirby »

Av gas is an alternative to "mo" fuel and of course no ethanol..but its damn expensive and you will probably have trouble fueling on the road trip! Not a practical thing at all.

Not only that it is actually not legal to use avgas for over road use 'cause of the road taxes that are not collected. Like agriculture/construction equipment that is not "road use", normally red in color and is much cheaper for that reason.

Airport FBO venders are not supposed to sell avgas that is pumped into a road going vehicle. (Of course some will).

Stock moto engines the higher oct will do no harm but will be no benefit. Higher oct for aircooled aircraft engines that operate all their lives at high power (above 65%) to prevent detionation not for more power.
(been around aircraft all my life, working on and flying.)
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Re: Aviation Fuel

Post by BadToTheBown »

riceburner wrote:
Barista wrote:...two different chemicals and have different affects on certain types of rubber. ... Avgas, or high octane fuel - it burns slower than lower octane fuels, and thus is better for high compression engines as it doesn't 'pre-detonate' - ie burn before it's meant to.
+1 Av gas is good for my 13.5:1 pistons in my R1150S, but Chris Hodgson (SJBMW) raced their R1200S bikes (12.5:1 compression ratio) on regular gas and made 2 more HP doing it over premium, go figure...sounds like going through the carbs and re-syncing them might be in order...
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Re: Aviation Fuel

Post by kirby »

Lower oct Gas, even at the pump has more BTUs per unit of mass/wt. than the higher oct. The detonation inhibitors in the higher oct (used to be mostly lead) is the reason.
I can get a fractional better mileage on 87 than 91 and the 87 is the freshest gas at the station. (careful measurement is required).

However if you NEED the higher oct because of "pinging" (pre detonation).

By all means!
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Re: Aviation Fuel

Post by AZBMWRIDER »

I've noticed that I get 4-5 miles more per gallon if I use 91 octane .
On regular 87 octane, 172 miles to low fuel warning, with 91, 192-196 miles until the fuel light comes on .
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Re: Aviation Fuel

Post by kirby »

I have had the opposite but not that much different, only a couple of miles per. I regularly ride 3500 to 4500 miles on a trip and much of it is sometimes on the slab. I can get a very accurate burn count doing the slab and almost always w/same kit (about 60 lbs. carried the same way so aerodynamics is not a factor for that but wind is a big factor. Run 800 miles w/tail wind. cross wind,head wind..done all that on one 10 day trip so get very good figures.

In heavy cross winds the low fuel light can vary some just from the angle. (lean)

My machines is always in good tune and a never leave on a trip w/o new tires. Always as smooth as possible and never over 10 over speed limit most times.
I never use 91 oct any more and I have an engineer friend thats in the oil business that tells me the difference between 89 and 91 is negligible.

Use the cheapest fuel available which is the freshest, important to me.
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Re: Aviation Fuel

Post by CycleRob »

About using AvGas, my aviation mechanic experience in the late 60's was with 4,000 HP GE turboshaft engines on the P3 Orion https://www.military.com/equipment/p-3c-orion) using JP-4 jet fuel (specialized kerosene). AVGas available on the NavalAirStation, which uses a larger amount of lead than road cars did, was used by some determined guys in their cars/bikes and it left a very white tell tale deposit inside the exhaust pipes. I have very fond memories of radial 9 cylinder air cooled helicopter engines starting up and idling for the engine warm-up very nearby, prior to taxing away. Using AvGas in any BMW bike newer than an AirHead will coat and kill the Catalyst honeycomb medium.
Like BadToTheBown said "Chris Hodgson (SJBMW) raced their R1200S bikes (12.5:1 compression ratio) on regular gas and made 2 more HP doing it over premium, go figure"
I found the same nearly 2HP gain when DynoJet100 testing a Kawasaki ZX-6R on Premium and weeks later again on Regular grade gasoline. That's with an assistant listening for engine pinging, of which there was none during 4,000 RPM 4th gear roll-ons, standing right near the bike's engine aside the elevated Dyno tester platform. We performed that test at the request of its owner, Anthony who had heard about the "phenomenon" and wanted some easy HP, and to our surprise he got it!
Also sound is Kirby's logic that the 87 octane is the freshest gas at the station.
My F800ST's engine management system allows Regular gas to be used and states there will be some reduction in HP (likely at lower RPMs only). I have used (Chevron/Shell/Texaco) Regular gas in it almost exclusively since new, some 30K miles ago.
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