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after reading everything on here and reading all my own thread over pretty much if you got the money and the correct jetting run race fuel.. if you dont want to mess with jetting just run pump gas. As my bike is jetted great i been running U4 in it im bout to buy U4.4 does anyone know if ill need to mess with jetting again or not? Once i jeted my bike running U4 i have not yet once touched the choke and starts by 3rd kick. im 210lbs and my bike has no problems pulling me all over the track. Im sold on race fuel!
 

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TNTminis867 said:
im just going off numbers MDK KTM gave me... they obviously know what they are talking about if they had a factory team i have had 2 pales of U4.2 run 2 jets apart from each other with the same reading on the RAD gage... yeah it makes more power than pump consistantly but still not worth the jetting hassle week in and week out for local races


Dude.. I don't want to call bull**** on this one.. but.. "bull****". You're doing something wrong if your jetting is wrong like that.



If you bought "race gas" that the dude down the street is making with some special sauce in his garage.. sure. But not real live race fuel. Unless the stuff is old as heck or possibly the plastic pour neck was broken or cracked. Either of those are possible, but otherwise, no chance did you do everything right. None.
 

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12:1 stroker on my atc...have to run min 100 or it will ping(detonate)..like a mofo..runs smoothest on 108 though



we try and run c12..but dam **** is expensive

so we just go to the VP station in town..the sell 100 out of the pump..bike runs good on it.
 

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jns855 said:
after reading everything on here and reading all my own thread over pretty much if you got the money and the correct jetting run race fuel.. if you dont want to mess with jetting just run pump gas. As my bike is jetted great i been running U4 in it im bout to buy U4.4 does anyone know if ill need to mess with jetting again or not? Once i jeted my bike running U4 i have not yet once touched the choke and starts by 3rd kick. im 210lbs and my bike has no problems pulling me all over the track. Im sold on race fuel!






Im sold on race fuel to we just got a fresh barrel of VP4.4 and bikes are runnin CLEEEAAANNNNNN ......
 

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avgas is designed for long stints of high rpm. wont really help a dirtbike out




So wrong. Do you even know what kind of RPM's a Lycoming or Continental run? I do, I fly for a living. In the PA31 I fly, we are limited to 2575 RPM's for 3 minutes, and 2400 continuous. Is that high RPM's? Not exactly. The reason for the high octane is the exact opposite of what you are saying. With the amount of power, and the large bore, cylinder pressures are usually high. Add a turbo charger that produces nearly twice the amount of atmospheric pressure (sometime I see nearly 50" of manifold pressure of take off), with no intercooler (to complex/takes up too much space) and the potential for detonation is HUGE! And the only reason the lead is in there is to help cushion detonation if it does happen.



Here are a few picturs from my FB page.



















Edit to add. I found a pic of the center stack/avionics. Look at the tach and MP gauges. This picture was taken on the ground, not running. Notice the MP gauge reads atmospheric pressure.



 

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Racing fules may work for some and yes they smell awesome but,you need to clean your carb out or it clogs things up faster.i used to drain the carb and have a different line to run some pump fule with carb cleaner through it after race day.
 

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waking up a dead thread:



87-91 octane fuel is fine for any engine running under 13.5:1 compression. the pressure is what causes detonation. higher octane is more resistant to pressure detonation



110+ octane would be for 13.6:1 and up



a higher octane will not make you faster (everybody likes to think so) a lower octane gas burns slower and cooler



a lower octane gas burns faster and hotter



myth bust: AV gas is fine for really any engine. its not designed to sustain high rpm for a long time for low oxygen environments or anything, i used to mix that 50/50 with chevron 91 octane and it worked awesome in my 2 stroke and 4 stroke. i have an airport less than 2 miles away.



in a stock style motor, race gas will do absolutely nothing but smell good. might burn cleaner and reduce buildup though. have a correctly jetted motor and it wont build up massive amounts of carbon



race gas is for race engines, nuff said. have an air cooled bike that runs real hot? run a higher octane. burns slower and cooler like i stated above
 
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