Octane Boosting

[Tim Senne]

Help!  I have read several recommendations for boosting octane of the (crappy) gas on the market these days.  The owners manual of my '85 KTM says "DO NOT USE OCTANE BOOSTERS OR GASOLINE CONTAINING ETHANOL OR METHANOL" or your connecting rod will break, your stock portfolio will go in the toilet, etc.  So, why then is it okay to put octane booster in my '71 Six-Day (which I just finished rebuilding), and what about gas with ethanol?  What is a good (safe) octane rating to use in the Six-Day (with/without booster)?  And how about the plug gap (NGK B8HS)? (Yes, I put the thing back together without a manual.)  
Many thanks!

 

[cward]

Hi Tim, Im a new member and dont know much about Penton's but I do know a good bit about newer 2 strobe motorcross bikes and some of my friends that race use aviation fuel. I have used it in my son's Honda CR250 and 125 race bike to. It is 100 octane low lead, very highly refined and burns very clean. It does not have the crappy additives in pump gas either ans usually cost about $2.50 gallon. Im restoring a 72 Penton 126 6 day and will run in it to. If anyone else has an opinion on this subject I would like to hear from them. Thanks, Curtis

curtis ward

[Dante]

whatever you do DON'T use the stuff in the small bottles at the auto parts. It's over 90% mineral spirits and will run as hot as a firecracker......No good for aircooled engines. The ethanol/methanol warning on your '85 model is because the eth/meth will deteriorate your fuel lines and any other rubber parts (needle valve tip etc.)



Edited by - dante on 04/03/2001  10:59:47 PM

[Larry Perkins]

In our race bikes both modern and vintage we run a 50-50 mixture of Premium unleaded and CAM gas.

 

[Olmy]

Good info for ya Si

 

[Roger Sibilsky]

Check this site out if you haven't already.Quite informative.Anybody remember Kent Howerton from the '70's??The Rhindstone Cowboy aboard the big Suzuki's??He owns VP Racing fuels.Scope it out.
//www.vpracingfuels.com

 

[Larry Perkins]

Do I remember Kent Howerton?  In the 60's and 70's I grew up and raced in the Austin, Texas area.  I went to High School with Steve Stackable and Jack Hicks.  At Lockhart I saw many great battles with Kent, who was from San Antonio.  Besides all the fast locals like Jackie O'Leary to line up on the 125 expert start you would face Stack, Howerton, and Steve Wise who was from McAllen.  Wise by the way had one VERY FAST 125 Penton before his factory days.  I saw it get torn down on a couple of occasions because it was too fast.  It was legal just all the tricks.  I had no idea then that this was the hayday of motocross.  It just seemed like racing at the time and boy was it fast.  Memories.  I didn't know that Kent owned VP.  Thanks for the info.

 

[Chris Brown]

George Erl of Uptite Racing (4 stroke tuning and Baja racing fame) says "Doctor your fuel with a gallon of racing fuel to 3 gallons of pump gas". That way your non-race engine won't detonate and wear out your reciprocating parts. Av-gas runs too hot, is a poor substitute, and octane boosters are not safe for reasons mentioned in the prior message.
Air cooled bikes depend a lot on the fuel for cooling, and the oil to lubricate the moving parts. An improper mixture is a sure  invitation for failure.
Chris Brown

 

[cward]

Sorry, but I disagree with your opinion on AV fuel running to hot. AV fuel is usually 100LL (100 octane low lead) the higher the octane the slower and COOLER the burn. AV fuel is more higher refined than pump gas and does not have all the crappy additives added to pump gas either. I know many people active in motocross and supercross that use AV fuel and have no problems.

curtis ward

[Roger Sibilsky]

A word about AV gas.AV gas may be high octane fuel,but it was designed to run in airplanes that see high altitude and reletively low rpm.It is also heavily oxygenated to compensate for the high altitude.Using AV gas will,to a slight degree,lean out the air fuel mixture.That is why air cooled bikes have a difficult time with it.It will run a bit hotter.The liquid bikes mask the hotter running temp.Besides,If you're not running high compression and advanced timing,there's no real advantage to running race gas.Almost all the new bikes manufactures recommend running 93 octane.Most of the time,running race gas is a mind over matter deal.Never really feel it in the seat of your pants.It sure does smell good though.Klotz Be'Nol and Union 76 100 octane is a racers perfume!!

 

[Dwight Rudder]

Being a pilot and racer, I agree with Roger on this one. If you are not running much higher compression and advanced timing you don't need race gas. Straight AV 100LL isn't good for your bike. If you blend some with good 93 oct. pump it will be OK. The Lead in the LL is higher than the old leaded car gas.
the mix will have a higher Octane than the sum of the 2 octanes /2. I used to run about 1 or 2 gals of AV LL to a 5 gallon can. Av gas will run some what cooler but too much octane will make your engine run FLAT. There is more power in low octane fuel than High octane fuel. The higher the Octane the slower the burn. Run only what it takes to not ping.
AV gas is designed for high altitude and steady rpm. It also has additives that might not be compatable with your 2 stroke oil. Some brands of AV gas ( Phillips 66 for example) will not allow Castor oil ( Maxima 927, Klotz , Bean oil, etc) to stay in suspension. I found out the hard way in my WWI Nieuport replica aeroplane. I crashed into a rice field. The best thing to do is use about a OZ. per Gal. of Maxima octane booster or PJ1 Octane booster. These are Toulene based and designed for motorcycle usage. There is no extra power in a stock engine using race gas. In fact the HP will be lower, if you run more than 105 oct.
Cher'o,
Dwight Rudder

7 time ISDT / E medalist
7 time National Enduro Class Champion.

[Chris Brown]

Curt and Dwight are on the money. Av-gas has a ton of additives for aircraft use only. To keep it from collecting water,to lubricate old carb systems, all kinds of reasons. You're just not getting your money's worth, and it could very well be harmful to your MC motor.
Trick race gas has a high lead content and quite high octane (114) so that mixing a gallon into each 4 gallons of pump gas will protect your motor from harmful effects of the poor quality of pump gas. And just announced here in CA, they are lowering premium to 91, taking the MTBE's out, and adding alcohol. None of this helps a bike motor. The newer 4 strokes are really hard hit with the hi-tech valve systems and their narrow seats.
Race gas also insures you will have at least decent fuel for your bike as pump gas is known to have unreliable consistency. Even occasional mild detonation has ill effects on engine logevity.
From a racer that knows: George Erl, 5 times Baja 500 winner, and respected race tuner.
Chris Brown
PS. Tolulene is bad news too. Known to run WAY hot.
Oh, and the plug gap for bikes is about 23 thousandths. The B8 is just fine.

 

[Dave Hefterich]

Then what is the answer? I was on VP's web site and there must be 20 different fuels to choose from. Is that 76 race gas any good? It must be unleaded because they sell it here in Ca. There is a station not to far from my house that is selling it for about $5.00 a gallon. Does it lose octane if it sits for a couple of weeks?

 

[Roger Sibilsky]

Plug gaps vary from engine size to state of tune.Union 76 is run in every car on the NASCAR Winston Cup circuit.If it didn't work,they would be using something else.Keep your gas stored in a cool,out of the sun area.Sun light destroys octane levels.Out here in MI. Union 76 sells for about $3.75 a gal.If you feel you need to run race gas,a 50/50 mix will be more than sufficiant.I myself would not store race fuel for more than 60 days.

 

[Dante]

Neighbor kid races the GNCC series (on a KTM), and uses Sunoco Race Fuel 1part to 4parts hi-test...never has failures