50/50 avgas mixed with 95?

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9/11/2019 11:22 PM

Been told to run this. Why would I do this?

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9/11/2019 11:55 PM

Because you've been told to.

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9/12/2019 12:02 AM

Burns cleaner, cooler, more efficient. Your bike will thank you for it.

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9/12/2019 3:38 AM

I’ve been running straight 100LL av gas in my last, I don’t know, 8 or 9 2-strokes. Never had one issue at all. Currently running it in my YZ125 and 250 mixed with Motul 800 at 36:1

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9/12/2019 3:40 AM

Is this in a 2/ or 4/

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9/12/2019 3:47 AM

About Avgas:

AvGas is short for Aviation Gasoline. AvGas is of interest to motoring enthusiasts because of its availability, octane rating and low price compared to commercial race fuels. AvGas might seem an obvious choice but closer study raises some doubt.

AvGas LL100 stands for "Low Lead 100 Octane". TEL (Tetra-ethyl-lead) is added to raise the octane. When used in a motor vehicle this fuel will leave a lot of lead deposits in the motor. 100LL has a high lead content (0.5 grams per litre), even higher than leaded race fuels. The deposits left when TEL(lead) is burned are corrosive and damaging to valves, valve guides, valve seats and cylinder heads. Lead deposits will also block oxygen(lambda) sensors and catalytic converters and foul spark plugs even after only a short use. Also, 100LL has a chemical package added to make it perform at high altitude, and that isn't the best thing for motor vehicle performance here on the ground.

AvGas is blended for large-bore, long-stroke, low RPM engines which run at high altitude. While AvGas' higher octane is useful, smaller-bore, shorter-stroke, high RPM engines will perform better on racing fuel or high quality octane boosters. AvGas has lower volatility so when used in proportions higher than about 40%, part-throttle drivability and cold starts may be compromised. AvGas has a lower specific gravity so it will require a change in air-fuel ratio calibration for the engine to perform at its best. LL100 is blended with a high percentage of aromatics causing reduced throttle response which is not an issue with an aircraft engine but certainly an issue in a high-performance automotive engine. These high levels of aromatics will also damage rubber components in automotive fuel systems such as fuel lines, fuel pump seals and injector washers.

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9/12/2019 4:38 AM

What bike are you putting it in?

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9/12/2019 4:57 AM
Edited Date/Time: 9/12/2019 4:58 AM

MP818 wrote:

I’ve been running straight 100LL av gas in my last, I don’t know, 8 or 9 2-strokes. Never had one issue at all. Currently running it in my YZ125 and 250 mixed with Motul 800 at 36:1

I like to mix straight av gas with BelRay Synthetic Si 36:1. The fuel is blue, and the oil is blue. Mixed together, that blue is deeper than Walter White's best and smells sweet as candy. I would fire my bike up in the house if it wouldn't piss my wife off.

It's $5 a gallon compared to whatever VP offers. Usually twice as much. VP is great, but I'm a weekend warrior, not an expert or pro. 100LL gets my money.

Oh, and don't put it in a 4 stroke. Only 2 strokes like 100LL.

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9/12/2019 5:22 AM

Has anyone run it in a 4 stroke? I can get non ethanol 88 octane, but would rather have a higher octane rating for my Kx450. Wondered if mixing them 50/50 would give good results?

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9/12/2019 5:46 AM

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9/12/2019 6:55 AM
Edited Date/Time: 9/12/2019 6:56 AM

I always hear about av gas not working optimally at low attitudes, but 2 of the most critical events during a flight happen a relatively low altitude.

Always puzzled me.

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Go for it! Don't let a little thing like fear, or common sense hold you back.

9/12/2019 7:11 AM

SEEMEFIRST wrote:

I always hear about av gas not working optimally at low attitudes, but 2 of the most critical events during a flight happen a relatively low altitude.

Always puzzled me.

I think that is one of those myths that sound believable to people, so they run with it and regurgitate it over and over as fact.

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9/12/2019 7:18 AM
Edited Date/Time: 9/12/2019 7:21 AM

SEEMEFIRST wrote:

I always hear about av gas not working optimally at low attitudes, but 2 of the most critical events during a flight happen a relatively low altitude.

Always puzzled me.

KHI Guy wrote:

I think that is one of those myths that sound believable to people, so they run with it and regurgitate it over and over as fact.

Exactly.
Probably started by race fuel companies.

That fuel is used extensively in small A/C, and most of those are flying around 3-4000 ft.

My guess is a fair amount of the members here ride at those altitudes.

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Go for it! Don't let a little thing like fear, or common sense hold you back.

9/12/2019 7:36 AM

Av Gas won't spoil for 10 years.

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9/12/2019 7:57 AM

Had to run at least a 50/50 gas mixture to get my YZ250 smoker to not ping.

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9/12/2019 8:17 AM

It's a decent choice for a smoker. Not as good performance wise as say C-12. I always could feel the throttle response was much better with C-12. Avgas is regulated so it's always consistent. Running it 50/50 will work fine.

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9/12/2019 8:27 AM

Interesting. I run vp110 cut with 88 ethanol free in my 144.

For how much fuel you use racing is it really that significant of a difference in cost savings ???

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GP740
Since 1987

9/12/2019 8:31 AM
Edited Date/Time: 9/12/2019 8:31 AM

Running straight AvGas 32:1 with Maxima Super-M through a Lectron carb on my 04' KX125 with a cut head. Runs great!

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9/12/2019 8:31 AM

I know my engine builder ran it back in my 2 strokes days. The bikes were fast, but they blew up a lot. One from piston detonation, not sure if it was fuel related at all.

I understand this post doesn’t really answer any of your questions lol

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9/12/2019 8:38 AM

Most vital advice threads don’t answer anything. Mostly just a buncha stories on what everyone does. And then someone will post a vid of Brandon’s first race if it gets real salty.

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GP740
Since 1987

9/12/2019 8:46 AM
Edited Date/Time: 9/12/2019 8:58 AM

Unless you have a modified engine, 95 octane is more than sufficient to eliminate detonation in any motocross bike. Since AV gas offers no performance advantage (it is not oxygenated), why bother?

https://nasaspeed.news/tech/engine/octane-vs-horsepower-separating-fact-from-myth-in-the-debate-over-which-fuel-makes-more-power/?amp

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9/12/2019 8:58 AM

Interesting reading: but, it starts out with someone having 95 Oct rated fuel available and then they mix it with AV gas? Seems to me a good fuel booster like VP's Octanium would do better, be more consistent and "cheaper"...?

Yesterday, I rode Twisted Development's '07 YZ 250 project that was based on a thrashed basket case that Jamie got from Austin Howell...it ran like a champ on the track and on amazing single track out behind Cahuilla...

It was running on VP's T2.

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I ripped a start from Egypt and I was happy about that.

9/12/2019 9:07 AM
Edited Date/Time: 9/12/2019 9:09 AM

TeamGreen wrote:

Interesting reading: but, it starts out with someone having 95 Oct rated fuel available and then they mix it with AV gas? Seems to me a good fuel booster like VP's Octanium would do better, be more consistent and "cheaper"...?

Yesterday, I rode Twisted Development's '07 YZ 250 project that was based on a thrashed basket case that Jamie got from Austin Howell...it ran like a champ on the track and on amazing single track out behind Cahuilla...

It was running on VP's T2.

VP T2 is, in fact, oxygenated. This is what led to the increase in performance that you felt, not the elevated octane rating. Since the fuel is oxygenated, it produces more power and burns more quickly. This requires a higher octane rating to prevent detonation.

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9/12/2019 9:14 AM

TeamGreen wrote:

Interesting reading: but, it starts out with someone having 95 Oct rated fuel available and then they mix it with AV gas? Seems to me a good fuel booster like VP's Octanium would do better, be more consistent and "cheaper"...?

Yesterday, I rode Twisted Development's '07 YZ 250 project that was based on a thrashed basket case that Jamie got from Austin Howell...it ran like a champ on the track and on amazing single track out behind Cahuilla...

It was running on VP's T2.

quadzrulebro wrote:

VP T2 is, in fact, oxygenated. This is what led to the increase in performance that you felt, not the elevated octane rating. Since the fuel is oxygenated, it produces more power and burns more quickly. This requires a higher octane rating to prevent detonation.

Oh, that's cool. Heck, I wasn't concerned about it's octane rating. I just know it works.
I've mixed it down to 60:1 (by using VPR) and have alway been impressed with the performance.

I've used it in everything from Husky TC125s and TE 150s to Jet Ski 550s.

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I ripped a start from Egypt and I was happy about that.

9/12/2019 9:40 AM

TeamGreen wrote:

Interesting reading: but, it starts out with someone having 95 Oct rated fuel available and then they mix it with AV gas? Seems to me a good fuel booster like VP's Octanium would do better, be more consistent and "cheaper"...?

Yesterday, I rode Twisted Development's '07 YZ 250 project that was based on a thrashed basket case that Jamie got from Austin Howell...it ran like a champ on the track and on amazing single track out behind Cahuilla...

It was running on VP's T2.

That's the advantage way too many people don't have. Running a bike built by a top tuner and can dyno and jet for the best performance. I don't know if OP has tried jetting and or different oils or fuel ratios. Is 95 in NZ the same as our 91? Does the gas have ethanol?
I ran AV gas in my YZ465 and my 05 CR250. 40:1 with Maxima SuperM. Both bikes ran horribly on pump gas. It was night and day difference running avgas in my bikes. I tried 50/50 C12 and pump 91 but could not tell the difference except for paying $70 for 5 gallons of C12. Avgas is about $18 for 5 gallons.

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The older I get, the faster I was.

9/12/2019 9:53 AM
Edited Date/Time: 9/12/2019 9:53 AM

TeamGreen wrote:

Interesting reading: but, it starts out with someone having 95 Oct rated fuel available and then they mix it with AV gas? Seems to me a good fuel booster like VP's Octanium would do better, be more consistent and "cheaper"...?

Yesterday, I rode Twisted Development's '07 YZ 250 project that was based on a thrashed basket case that Jamie got from Austin Howell...it ran like a champ on the track and on amazing single track out behind Cahuilla...

It was running on VP's T2.

captmoto wrote:

That's the advantage way too many people don't have. Running a bike built by a top tuner and can dyno and jet for the best performance. I don't know if OP has tried jetting and or different oils or fuel ratios. Is 95 in NZ the same as our 91? Does the gas have ethanol?
I ran AV gas in my YZ465 and my 05 CR250. 40:1 with Maxima SuperM. Both bikes ran horribly on pump gas. It was night and day difference running avgas in my bikes. I tried 50/50 C12 and pump 91 but could not tell the difference except for paying $70 for 5 gallons of C12. Avgas is about $18 for 5 gallons.

Good point.

I went on to comment on T2 working on other stock bikes and even my old-school Jet Skis.

Octanium is $20 a can and I mix it into 10 gallons. The best part is I can do it one gallon (or even less) at a time. It keeps well in the steel can it comes in. I tested it, initially, on a stock RMZ 450 w/ Yosh pipe: it made California pump gas much better and eliminated "pump pop" that the RMZ with a white-plug (map) can get.

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I ripped a start from Egypt and I was happy about that.

9/12/2019 10:12 AM
Edited Date/Time: 9/12/2019 10:36 AM

The timing of this thread is well, as I just picked up a mildly built 150SX Tuesday night that’s jetted for c12 or 110 (50/50). I have access to 100LL AVGAS that’s less than a mile away. I’d always ran that in my two strokes and now I’m wondering if I could run that 50/50 instead of trying to find a somewhat local supplier of c12 or driving a half hour to get Sunoco 110 at the pump.

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9/12/2019 11:18 AM

SEEMEFIRST wrote:

I always hear about av gas not working optimally at low attitudes, but 2 of the most critical events during a flight happen a relatively low altitude.

Always puzzled me.

KHI Guy wrote:

I think that is one of those myths that sound believable to people, so they run with it and regurgitate it over and over as fact.

SEEMEFIRST wrote:

Exactly.
Probably started by race fuel companies.

That fuel is used extensively in small A/C, and most of those are flying around 3-4000 ft.

My guess is a fair amount of the members here ride at those altitudes.

Avgas has a relatively low RVP (reed vapor pressure), meaning at low elevations where baro pressure is highest the fuel will have very low volatility and be slower to vaporize. As you go up in elevation and the baro pressure comes down the delta between the fuels RVP and the atmosphere is reduced, hence the volatility goes up along with fuel vaporization.

At the end of the day though this would mainly be an issue at low elevations and when used on cold days. Seeing as dirt bikes arn't exactly a winter toy with some exceptions Avgas will do fine for most.

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9/12/2019 11:54 AM

I have been running it since 1975 in my 2 Strokes, never had a problem and it lasts forever. My bikes have mods so they grenade on pump gas pinging so hard.

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9/12/2019 12:09 PM

This fuel mix may lessen the performance of a modern 4 stroke engine as the octane will be higher than what is needed and will burn slower.

Paw Paw

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