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Old 01-15-2012, 09:21 PM   #16
Dukeryder
 
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I wouldn't use AVGas in my bike. Too much lead to foul plugs plus the stuff's quality isn't that consistent.

Sunoco or 76 sell 100 octane race gas. Some bike shops and Cycle Gear sell it in metal cans.
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Old 01-16-2012, 02:33 PM   #17
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Quote:
Originally Posted by Dukeryder View Post
I wouldn't use AVGas in my bike. Too much lead to foul plugs plus the stuff's quality isn't that consistent.
Examples?

I make my fuel in 5 gallon batches. 3 gallons 100LL avgas to 2 gallons ethanol-free supreme. Never had a fouled plug. I learned this from a guy who's been riding trials since Greeves made bikes, and he's never had issues either.

The only other thing I might try is Torco's Unleaded Accelerator in pump gas.
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Old 01-16-2012, 02:34 PM   #18
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Originally Posted by BikePilot View Post

Also note that measuring compression ratio is a bit funny on two strokes. Do you measure head volume as a percentage of total displacement or just swept area above the ceiling of the exhaust port? What if the exhaust port ceiling moves with rpm?
Good point. There's a big difference between BDC and above the ports. Someone will be along presently to clear this up...
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Old 01-16-2012, 02:50 PM   #19
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Quote:
Originally Posted by Dukeryder View Post
I wouldn't use AVGas in my bike. Too much lead to foul plugs plus the stuff's quality isn't that consistent.

Sunoco or 76 sell 100 octane race gas. Some bike shops and Cycle Gear sell it in metal cans.
I have heard lots of "don't use AvGas" but nobody has been able to tell me exactly why. I have found plenty of people who have been using it for years without issue. I have been using AvGas since late summer with no problems.

I was using VP fuel at $9/gal with great results. The price went up to $15/gal over the summer. AvGas is $5.50/gal.

There is no ethanol free fuel available at the pump anywhere near me (yes, I've checked the websites ). My Scorpa tank cannot withstand ethanol.

I will continue to use AvGas until I see some solid evidence as to why I should not.

YMMV!
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Old 01-16-2012, 05:17 PM   #20
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Quote:
Originally Posted by motojunky View Post
I have heard lots of "don't use AvGas" but nobody has been able to tell me exactly why. I have found plenty of people who have been using it for years without issue. I have been using AvGas since late summer with no problems.

I was using VP fuel at $9/gal with great results. The price went up to $15/gal over the summer. AvGas is $5.50/gal.

There is no ethanol free fuel available at the pump anywhere near me (yes, I've checked the websites ). My Scorpa tank cannot withstand ethanol.

I will continue to use AvGas until I see some solid evidence as to why I should not.

YMMV!
The only "don't use AV gas" I have heard issues with is trying to use it in a high RPM engine. Something about flame speed
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Old 01-16-2012, 06:36 PM   #21
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Probably a non-issue on most trials bikes, but leaded fuels do not play well with catalytic converters.

Quote:
Originally Posted by motojunky View Post
I have heard lots of "don't use AvGas" but nobody has been able to tell me exactly why. I have found plenty of people who have been using it for years without issue. I have been using AvGas since late summer with no problems.

I was using VP fuel at $9/gal with great results. The price went up to $15/gal over the summer. AvGas is $5.50/gal.

There is no ethanol free fuel available at the pump anywhere near me (yes, I've checked the websites ). My Scorpa tank cannot withstand ethanol.

I will continue to use AvGas until I see some solid evidence as to why I should not.

YMMV!
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Old 01-16-2012, 07:09 PM   #22
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The lead can foul up the spark plug. Back when I was working toward my A&P I had to clean plugs with a special sand blaster to get the lead off the electrode and often times the plugs were fouled from the lead.

I also used to be a mechanic for a SCCA Pro racing team, most of the cars we ran had to run pump gas, but we had a couple Production class cars that we'd run occasionally and I asked the boss why the hell we didn't run AVgas as it was $2/gal instead of the $4/gal Race Gas. He said that he had tested AVgas and that the Octane Ratings fluctuated quite a bit off the stated 100. These fluctuations in fuel quality are not a big deal in an aircraft because you adjust fuel/air mixture in your aircraft as you fly depending on altitude and temperature. You don't wanna rejet for every tank of fuel. The issue of running it in an engine revving 7K RPM when it's meant for an engine running <3K was also brought up as well.

The AVgas might be ok in the trials bike, especially if the alternative is running ethanol junk.
Check this site for non-ethanol gas
http://pure-gas.org/index.jsp?stateprov=WY
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Old 02-14-2012, 09:43 AM   #23
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Originally Posted by Dukeryder View Post
The lead can foul up the spark plug. Back when I was working toward my A&P I had to clean plugs with a special sand blaster to get the lead off the electrode and often times the plugs were fouled from the lead.

I also used to be a mechanic for a SCCA Pro racing team, most of the cars we ran had to run pump gas, but we had a couple Production class cars that we'd run occasionally and I asked the boss why the hell we didn't run AVgas as it was $2/gal instead of the $4/gal Race Gas. He said that he had tested AVgas and that the Octane Ratings fluctuated quite a bit off the stated 100. These fluctuations in fuel quality are not a big deal in an aircraft because you adjust fuel/air mixture in your aircraft as you fly depending on altitude and temperature. You don't wanna rejet for every tank of fuel. The issue of running it in an engine revving 7K RPM when it's meant for an engine running <3K was also brought up as well.

The AVgas might be ok in the trials bike, especially if the alternative is running ethanol junk.
Check this site for non-ethanol gas
http://pure-gas.org/index.jsp?stateprov=WY
AV gas can discolor clear plastic fuel tanks- but beyond that- I don't know any other reason not to use it. I read that AVgas octane is more consistent than pump gas.
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Old 02-14-2012, 11:05 AM   #24
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Corrected compression ratio on most common 2T motors is measured from the closure of the exhaust port, and on a trials bike is probably going to be around 7-8:1.

In most cases a trials bike will run fine on pump fuel, but use of high octane fuels tend to reduce the effects of jetting thats not quite right, and exhaust systems which may not have been serviced in a long while.

The main reason for using race fuel is to slow down the combustion process, and lessen the likelihood of detonation in motors which are running very high compression ratios.
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Old 02-14-2012, 11:16 AM   #25
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Originally Posted by Twin-shocker View Post

The main reason for using race fuel is to slow down the combustion process, and lessen the likelihood of detonation in motors which are running very high compression ratios.
It's all about the ethanol...
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Old 02-14-2012, 11:48 AM   #26
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For ethanol free fuel, go to www.pure-gas.org. There is a list of dealers and stations by geographic location. If you desire race gas, VP will UPS it to your door for a nominal fee.
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Old 02-14-2012, 01:48 PM   #27
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Originally Posted by Willie B View Post
For ethanol free fuel, go to www.pure-gas.org. There is a list of dealers and stations by geographic location. If you desire race gas, VP will UPS it to your door for a nominal fee.
I started to compose a reply before realizing that I already had, just a few posts back in this same thread. A little cut and paste and voila! I will add that there was a local(ish) station listed as being ethanol free last year, but I tested the fuel and found that it did contain ethanol. It is gone from the websites now. Be careful trusting those websites...

My earlier reply:

I have heard lots of "don't use AvGas" but nobody has been able to tell me exactly why. I have found plenty of people who have been using it for years without issue. I have been using AvGas since late summer with no problems.

I was using VP fuel at $9/gal with great results. The price went up to $15/gal over the summer. AvGas is $5.50/gal.

There is no ethanol free fuel available at the pump anywhere near me (yes, I've checked the websites ). My Scorpa tank cannot withstand ethanol.

I will continue to use AvGas until I see some solid evidence as to why I should not.

YMMV!
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Old 02-14-2012, 03:55 PM   #28
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Originally Posted by motojunky View Post
I started to compose a reply before realizing that I already had, just a few posts back in this same thread. A little cut and paste and voila! I will add that there was a local(ish) station listed as being ethanol free last year, but I tested the fuel and found that it did contain ethanol. It is gone from the websites now. Be careful trusting those websites...

My earlier reply:

I have heard lots of "don't use AvGas" but nobody has been able to tell me exactly why. I have found plenty of people who have been using it for years without issue. I have been using AvGas since late summer with no problems.

I was using VP fuel at $9/gal with great results. The price went up to $15/gal over the summer. AvGas is $5.50/gal.

There is no ethanol free fuel available at the pump anywhere near me (yes, I've checked the websites ). My Scorpa tank cannot withstand ethanol.

I will continue to use AvGas until I see some solid evidence as to why I should not.

YMMV!
Is your Scorpa tank GRP rather than HDPE plastic then?
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Old 02-14-2012, 04:23 PM   #29
motojunky
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Originally Posted by Twin-shocker View Post
Is your Scorpa tank GRP rather than HDPE plastic then?
I don't know what it is... I just know that ethanol eats away at the inside of the tank. In the short term it gunks up the carb - long term = new tank.

I use pump gas in my other bikes without issue.
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Old 02-23-2012, 06:46 PM   #30
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Originally Posted by GasGas300 View Post
I like to mix my fuel at 70;1 oil and use half non ethanol premium and half race gas - But I can only find race fuel in 5 gallon containers. Now, if I was retired or had fewer other bikesto ride, I might be able to burn 10 gallons of gas before the race gas goes bad. But that is not the case.

Anyone know where I can get race fuel by the gallon?
These guys will ship it to your door. 93 octane no ethenol. 3 year shelf life. I have been using it (40:1) for some time in my three 1966 Bultaco's no problems. You could buy the 4t and add your own oil ratio to it.
http://www.trufuel50.com/

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