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I have a mod 65 that has to run 100 octane or better. Due to last minute and my irresponsibility I’ve ran out of c12. The quickest option is the local airport 100ll avgas. Bike has always ran 110 octane 50/50 with non ethanol 93 and amsoil dominator 50:1. Any issues with burning the avgas for the weekend?
No issues with running the AvGas. It may jet slightly different.
C12 has a MON rating of 108. A 93 octane pump gas with 10% ethanol is around 88 MON. (88+108)/2 = 98 octane as your current baseline. AVGAS octane is about 103 on the MON scale, so you are covered detonation wise. That is independent of jetting though. For jetting, I think density would be the most obvious thing to compare. AVGAS is about the same as C12, jetting wise if the bike runs ok on pure C12 it should be fine on AVGAS.
Avgas runs great!
I've seen endless online arguments about using AVgas, but I have used it with no issues. I run straight 100LL in my vintage 2-stroke Elsinore which has a bit higher compression than stock, but do 50/50 with 90 octane non-ethanol (which should be about 95 octane) in my stock YZ450F. Stock modern engines don't need any more than 95 octane. I laughed when people say it's blended to produce the most power at higher elevations when you need the most power taking off from ground level. Also, many race fuels use AVgas as a base and add their additives.
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The bike isn’t jetted for c12. It’s jetted to run c12 mixed 50/50 with 93 pump. Any idea if it leans it or richs up. It’s dialed in on the c12 mix. May have be able to get the c12 early tomorrow so maybe we won’t even have to worry with it
I threw the pure C12 out there in case you've ever tried it.
Looking at a standard orifice equation, you'll get about 2.4% more flow with AVGAS than just pump gas, so about 1.2% compared to your 50/50 mix. 1% is roughly the same as a 20 degree F temperature change or going from sea level to about 1600 feet elevation.
Was the cheapest performance gas for our 2 strokes back in the day and the bikes loved it. I ran all the time!
Dude are you a chemist with a mechanical engineering degree…: So do you think the current jetting will be close?
They really depends on how close it is to begin with under the conditions you'll be in. If it was perfect before, it will probably be fine or just need the air screw turned. If it was already off, you may need a needle clip and pilot change.
AVGas will be fine to run. For best power, AVgas likes to be on the lean side, and likes compression. So, if you are running a 50/50 blend of C12 and pump, I would lean it out a bit for the AVgas
I ran 2 yr old bulk c12 this past summer. The bike ran Great
It was in a steel can though
I’ve been jetting like crazy on my sons 50sx lately. I bet you’ll be just a tad rich with this change, but the 65sx isn’t as finicky so I think you’ll be just fine.
I had jetting issues on our 23 gas gas 50. Best money spent on it was the pax spec carb. Mostly do woods racing so wasn’t a need to be ama legal
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