On the subject of race gas

[delphipro5]

I am convinced I need to run some sort of race gas in my bike after the rebuild (reference thread: monument to the 2-stroke - to see the build.)
I am just wondering what it is that you need to change and why. I am getting the head modified to run it and the carb work is being tailored to it as well. I would just like to Know what the differences are that need to be done and why.
I belive it will be better for the bike to be running a high octane leaded racing fuel as opposed to the crappy 10% ethanol 91 oct. junk I get out of the pumps up here! That stuff gums up EVERYTHING! Am I right about that??
 I know these bikes prefer a high oct. fuel, and the benifits of lead in keeping the engine running smooth sounds a lot better than using crap pump gas to me. I am planning on getting some of VP's U4.4 to use. Do you still mix it with oil the same way you do reg. pump fuel? Also what are the chances of getting false detonation and blowing your engine with this stuff?? THAT I DO NOT WANT! I figured the bike would thank me if I led it away from the general watering hole and gave it bottled water instead! But I don't want to have it drinking posion ethier!

Just loooking for some insight and intel. lemme know whatcha think.

[kaw rider]

What type of riding you do and list your mods.

[Rd]

100LL is an alternative about $4.25 gal

[Motorrad]

100LL is an alternative about $4.25 gal

And like all race fuel. Requires differant jetting...  And a few 2 stroke oils SEPERATE in it

[kxpegger]

100LL is an alternative about $4.25 gal

http://www.generalaviationnews.com/2009/11/29/preparing-for-the-end-of-100ll/

[Rd]

http://www.generalaviationnews.com/2009/11/29/preparing-for-the-end-of-100ll/

100ll may be a short term alternative and requires rejetting

[Motorrad]

d**n EPA strikes again..  Bastards

[sandblaster]

Well, it's only time and money to figure out what to use next 

[Hillclimb#42]

Well, there is a great search function for most if not all of the modification questions. The fuel question is a good one. Its my understanding that running the octane that your motor needs is the seceret. When modifying the head, to add compression, your chances of pre-ignition increase. The added compression will ignite the fuel before the spark plug, causing a double fire, which interefere with each other. The results can be anywhere from a new noise to an engine failure.
Pump gas is pretty much junk anymore. The ethanol content really draws moisture, and there is no way to know, if the fuel is fresh fuel. All fuels degrade with exposure to heat, light and air, so its as important to run fresh, clean fuel as possible to have high  enough octane for the new head mods.
Buying fuel with too high of an octane will not cause any damage to my knowledge, but will result in not using all of the potential of that fuel. It may actually hurt performance slightly. Oxygenated fuels are known to be more maintenance. The oxygenated parts are ethers, which evaporate quickly. When the ethers burn the by product is oxygen which is great for combustion. The maintenace comes in when you're done riding. Most guys will drain their fuel to capture as much of the performance as possible in their fuel cans. All Vp fuels come in a sealed metal container which seals their fuel to maintain all of its performance qualities. For the most part, a stock engine can live on pump gas with no issues. The freshness seem to be the important quality there. The shop altering your head should be qualified to also recommend a fuel octane. If you trust them with the head mod, then it should be easy enough to hear their advice about it. No matter what, keep your fuel protected. Out of the sun, in a sealed metal container, do not stock pile quanities, whatever you can do to keep it fresh and clean. They recommend going up 2 main sizes on both the main and slowjet. Thats probably the best way to jet anything start fat, and lean down until all bogging goes away. Too lean will definately melt her down. Do frequent plug checks, until you're positive that you got it right.
Camm II -110-leaded
Turbo Blue -110
Vp C12 -108-leaded non-oxygenated   compression ratios under 15:1
Vp-u4.4 -103-leaded and oxygenated

[delphipro5]

Good stuff hillclimb#42! Wow this is tough for me to figure what I want to do! So, if im getting this right, the C12 and the vp110 has a higher octaine rating than the U4.4.. and in turn will need a higher compression to detonate, which means increased chance of false detonation? Also, they say that U4.4 designed to be a direct replacement for pump gas, so not much should need to be done in the way of compression to run it. right? Well I have been back and forth on this thing and I don't like the idea of having to drain the tank and carb. after every ride BUT it is not that tough to do really. And I know that It is a lot of $$ for fuel but I think it is worth it to get consistencey.  SO...... U4.4 it is!

[delphipro5]

After more thought I am thinking maybe 100LL AV may be the answer. I can prob. get it locally and store and use it rather easily. I NEED to figure this out because I have my Carb. at Dick's racing and I NEED to specifiy which fuel I will be using so they can jet it accordingly. How would I go about telling them I plan on using AV fuel? Will they be cool with that? Also I am sending my head to Larry Wiechman to have his Comp. Re. done and also the head work, so I will need to specify with him also the fuel used so he can machine it accordingly. Down to the wire now, so I need to figure this out this week by wed. 

[kaw rider]

after you get your carb back from Dick's you will have to still rejet it because the K5 jetting will change with mods to motor or how well your motor runs.

[Hillclimb#42]

The octane numbers are a little wacky, delphi. When it comes to the octane numbers and oxygenated fuels, there are alot of things to know and understand. The lower octane number of the u4 is a little deceptive. Its oxygenated properties make that a very effecient fuel that has a tremendous burn rate. Its similar to adding a supercharger, in a way, because you are adding oxygen into the actual combustion. Its not exactly clear to me what fuel is required per what mods. It has been stated many times that it depends on what your motor has done to it, but I have never really got a straight answer on what formula or process takes you to which octane. I had originally thought that the better, highest octane would be the best performance. There is another school of thought, that you just run high enough octane to get the job done, so as not to waste money on something not adding to performance.
  My eventual take on it is, C12 and U4.4 are both awesome fuels. U4 would likely out perform c12 or pump gas, in any motor. The 100LL I have no idea about. There is some confusion in my mind, if a higher octane than 100-110 would be "needed", but guys that have dynos have posted that the Q16 (116+, oxygenated and leaded) shows even better numbers. In general, pump gas is crappy and getting worse. All fuels will be less potent after exposure, but its not a major ordeal, like it seems. Exposed race fuel that has evaporated some, will still be good fuel. Its just that leaving it to vent in your tank, seems silly after you think about it. VP sells and stores every fuel in a sealed metal can, because its the only way to deliver it fresh to you. If you are riding the next day or two, it would be fine in the tank, IMO, just no reason to leave it for a month, race fuel or pump gas.

Jetting varies so much, for someone to tell you exactly what jets that you need would be tough. Some things will make the motor need leaner jetting and others  fatter jetting. Thats a deep subject. I think for the most part you are over thinking it. 100-110 octane is not much different from pump gas. I doubt these or c12 needs jetted much, if at all, and the U4 is probably only up one on the main. The trick is to be ready with a couple sizes of jets and be ready to get knee deep in the carb. Maybe go up one to start and see how it runs on a WFO run. Check plug and really listen and feel how the power comes on, and what it says when tapped. It may take a few runs, but once set-up, it won't change all of the time.
  Snows melting...., its almost time for dirt slingin'...

[delphipro5]

I think I have come to a conclusion.
 The U4.4 is ROUGHLY the same OCT. as the 100LL, yes it is oxy'd but for the most part they shoud both be able to be used with little to no increase in the compression, which means I don't need to go nuts on my dome. Even VP says that U4.4 is to be a direct replacement for pump gas with min. Carb changes ( +2) . And for the most part I THINK I will be using 100LL, IF I can get it at my local airport readily without issue. That I will be finding out early this week! So I don't think I need to freak out calling dicks and telling then to stop everything, I will just call them and tell them what it is I am using and they can get the carb. close. U4.4 and 100LL should be close on thier jetting and if not, no big deal I will just have to jet myself to dial in.
As far as the head work I will specify what it is I will be using and that I really don't want to increase the compression by much. Idealiy I would like to be able to build this to run 100LL, to 50/50 pump 91-100LL(mix), to U4.4 - with nothing more than jetting changes. Which should be doable to my understanding.

If I can come about 100LL with ease this week then that is what I will start with, and work from there. I never thought picking a fuel would be so tough! But they have made it that way with having junk pump gas! 

[kaw rider]

becareful with U4.4 and other vp fuels it doesnt like hot weather or it will vapor lock.