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2014 yz250f question

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I have a new yz250f and getting ethanol free fuel is sometimes tricky(will not use ethanol blended fuel) but vp u4.4 is readily available in 5 gallon pails at a few dealers around the area, so I am curious if its safe to use, I have read a lot about lead being bad for four strokes bit everyone says u4.4 is great fuel. I have searched this but never came up with a real solid answer, so can I safely run this fuel without concern or will it cause damage, I am not looking for a full time replacement for pump fuel just a safe alternative for occasional use when needed.

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I too was looking into this. It is fine to run in your bike and is what I had planned on running in mine until I talked to my dyno tuner. I am having him map the bike to run on premium pump gas and a second map to run MR12. He said the U4.4 isn't as stable as the MR12 and he is getting up to a 15% increase in power with the MR12 and correct mapping for running it. I will be testing on the dyno in a couple of weeks. Hopefully I can post results on here when it's all done.

Edited by Charlie755

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Badass Charlie!! :)

I'm really interested in your results. I'm really eying trading in the 09 for one of these "new fangled efi's ".

I'm keeping up with all the testing etc.

Way cool

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we have been using 4.4 since the bike was new with no problems,and if im not mistaken its spose to produce the most power of any of vp fuels,but i really cant say if thats the case on the new yammie since we never tried mr-12.the only other vp fuel that i have any experience with is the pro 5,and now the pro 6.the last three years i built the 250f kawi motors for brothers kyle and jason hussey who raced the lites east,since the fuel rules do not allow 4.4 at the pro level,we did all of our mapping and engine configurations on pro 5,then with pro 6 when vp changed up the formula.i do have a buddy that races the extreme dirt track series on a highly modded 450 honda with a calculated comp ratio of 16.8 to 1,and he runs the mr12 exusively.i think that i may have mentioned before,that on any 250f running on 4.4 fuel,you should see a nice little H.P.increase of up to 1.5H.P.It seems like our new yammie wants all of the fuel you can give it with the power tuner,wich leads me to beleive that the get system with the second injector like the kawi uses,might be the way to go if your really looking to build a true pro-level motor with all of the head work,cams,and piston.along with a carrilo rod,and superfinished internals.If you do build your motor to that level,then you would probly want to use mr12.For us,im stickin with the 4.4,our bike runs great on it.

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on a side note,the 4.4 will leave a light brownish coating on the exhaust valves,which is the burned lead and oxygenates.the pump fuel,and some of the unleaded non-oxygenated race fuels will leave a black gooey carbon like substance on the valves,but either way you are safe to use any of the vp or sunoco or renegade 4stroke compatible fuels.i personally dont trust the pump fuels in our area,(but thats a whole diff subject.lol)i know that all of the four strokes will run on pump fuel,but the new efi systems dont like the dirt and water that are associated with them.hope this helps you out.peace and wheelies!

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If you go with a non oxygenated race fuel,i would try the jay marmount map.with the 4.4 fuel you need to add about ten to 15 percent more fuel on each cell,except the first fuel cell,we left that at 0.The timing is more to dictate the way you like your power.(ie-snappy or more of a smooth long pull,or maybe for slick trac conditions)i dont know how to post up a map,or i would.i just came up with another map for the 4.4 that we will test tomorrow at the track,i will let you know if it works well.

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we have been using 4.4 since the bike was new with no problems,and if im not mistaken its spose to produce the most power of any of vp fuels,but i really cant say if thats the case on the new yammie since we never tried mr-12.the only other vp fuel that i have any experience with is the pro 5,and now the pro 6.the last three years i built the 250f kawi motors for brothers kyle and jason hussey who raced the lites east,since the fuel rules do not allow 4.4 at the pro level,we did all of our mapping and engine configurations on pro 5,then with pro 6 when vp changed up the formula.i do have a buddy that races the extreme dirt track series on a highly modded 450 honda with a calculated comp ratio of 16.8 to 1,and he runs the mr12 exusively.i think that i may have mentioned before,that on any 250f running on 4.4 fuel,you should see a nice little H.P.increase of up to 1.5H.P.It seems like our new yammie wants all of the fuel you can give it with the power tuner,wich leads me to beleive that the get system with the second injector like the kawi uses,might be the way to go if your really looking to build a true pro-level motor with all of the head work,cams,and piston.along with a carrilo rod,and superfinished internals.If you do build your motor to that level,then you would probly want to use mr12.For us,im stickin with the 4.4,our bike runs great on it.

I always do a lot of research on anything I'm going to do engine wise. From what my dyno guy is telling me you can get 5-7% more power out of the MR12 than U4.4. This is with having a properly mapped engine. I am using a power commander V as it it way more tunable than o Vortex or GYTR. He is able to dyno tune in 250 RPM increments. Also note that MR12 is a lower octane fuel (I believe it's around 85 Octane.) So I won't be running a high compression piston.

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thanks guys for the response, fuel is a major concern with me and I am sure everyone these days with this crap pump gas we have now, u4.4 only interests me because its super easy to get, one of my local dealers stocks it all the time and since I can buy it in small amounts im not worried about stability, another dealer stocks renegade p95 sometimes which looks to be safe, as far as I can tell its just a 95 octane unleaded pump alternative so I may give that a shot, but vp is easy to get so why not, the bike wont stay stock for long and with the lack of time to put a lot of hours on I don't mind paying a premium for fuel.

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Badass Charlie!! :)

I'm really interested in your results. I'm really eying trading in the 09 for one of these "new fangled efi's ".

I'm keeping up with all the testing etc.

Way cool

Just an FYI. I held on to my 08 in hopes that Yamaha was gonna come out with a fuel injected 250F in 2011 or 2012. I told myself if they didn't come out with one in 2014 I was going to buy a Honda. I found out I think in September/October Yamaha was going FI on the 2014. Then when I saw pics and found out more details I put my 08 up for sale in December and sold it. I am really excited about this new bike and will share anything I find out about it.

Lastly I think it was dirt rider that did dyno runs on all the 2014 250F's and the YZ came in a close second to only KTM and was putting out 36.66 HP at the rear wheel. Pretty impressive from the 34.5 HP my old 08 was putting out. The 14 puts power out where I like it to be too. It pulls harder from mid to top end which is how I like to ride the 250F's. Not bouncing off the rev limiter but around 10,500-12,500 rpm.

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